Tor (network)

The core principle of Tor, known as onion routing, was developed in the mid-1990s by United States Naval Research Laboratory employees, mathematician Paul Syverson, and computer scientists Michael G. Reed and David Goldschlag, to protect American intelligence communications online. Onion routing is implemented by means of encryption in the application layer of the communication protocol stack, nested like the layers of an onion. The alpha version of Tor, developed by Syverson and computer scientists Roger Dingledine and Nick Mathewson and then called The Onion Routing project (which was later given the acronym "Tor"), was launched on 20 September 2002.{{cite web |title=History |url=https://www.torproject.org/about/history/ |website=Tor Project |access-date=5 June 2021 |archive-date=13 January 2023 |archive-url=https://web.archive.org/web/20230113015314/https://www.torproject.org/about/history/ |url-status=live }} The first public release occurred a year later.{{Cite mailing list|mailing-list=tor-dev|last=Dingledine|first=Rogert|date=8 October 2003|title=Tor is free|publisher=Tor Project|url=https://lists.torproject.org/pipermail/tor-dev/2003-October/002185.html|access-date=23 September 2016|archive-date=13 February 2017|archive-url=https://web.archive.org/web/20170213031700/https://lists.torproject.org/pipermail/tor-dev/2003-October/002185.html|url-status=live}}

{{Anchor|Tor project}}

In 2004, the Naval Research Laboratory released the code for Tor under a free license, and the Electronic Frontier Foundation (EFF) began funding Dingledine and Mathewson to continue its development. In 2006, Dingledine, Mathewson, and five others founded The Tor Project, a Massachusetts-based 501(c)(3) research-education nonprofit organization responsible for maintaining Tor. The EFF acted as The Tor Project's fiscal sponsor in its early years, and early financial supporters included the U.S. Bureau of Democracy, Human Rights, and Labor and International Broadcasting Bureau, Internews, Human Rights Watch, the University of Cambridge, Google, and Netherlands-based Stichting NLnet.{{cite web|date=2009|title=Tor Project Form 990 2008|url=https://www.torproject.org/about/findoc/2008-TorProject-Form990.pdf|url-status=dead|archive-url=https://web.archive.org/web/20170629102518/https://www.torproject.org/about/findoc/2008-TorProject-Form990.pdf|archive-date=29 June 2017|access-date=30 August 2014|website=Tor Project}}{{cite web|date=2010|title=Tor Project Form 990 2009|url=https://www.torproject.org/about/findoc/2009-TorProject-Form990andPC.pdf|url-status=dead|archive-url=https://web.archive.org/web/20170629102506/https://www.torproject.org/about/findoc/2009-TorProject-Form990andPC.pdf|archive-date=29 June 2017|access-date=30 August 2014|website=Tor Project}} File:Geographies of Tor.png illustrating Tor usage in 2013]]

Over the course of its existence, various Tor vulnerabilities have been discovered and occasionally exploited. Attacks against Tor are an active area of academic research{{cite web|last=Goodin|first=Dan|date=22 July 2014|title=Tor developers vow to fix bug that can uncloak users|url=https://arstechnica.com/security/2014/07/tor-developers-vow-to-fix-bug-that-can-uncloak-users/|url-status=live|archive-url=https://web.archive.org/web/20170708090704/https://arstechnica.com/security/2014/07/tor-developers-vow-to-fix-bug-that-can-uncloak-users/|archive-date=8 July 2017|access-date=15 June 2017|website=Ars Technica}}{{cite web|title=Selected Papers in Anonymity|url=http://freehaven.net/anonbib/#2014|url-status=live|archive-url=https://web.archive.org/web/20180712134223/https://www.freehaven.net/anonbib/#2014|archive-date=12 July 2018|access-date=26 October 2005|website=Free Haven}} that is welcomed by The Tor Project itself.{{cite web|title=Tor Research Home|url=https://research.torproject.org/|url-status=live|archive-url=https://web.archive.org/web/20180626053025/https://research.torproject.org/|archive-date=26 June 2018|access-date=31 July 2014|publisher=torproject.org}}

{{Further|Dark web}}

{{Hidden services 2016}}

Tor enables its users to surf the Internet, chat and send instant messages anonymously, and is used by a wide variety of people for both licit and illicit purposes.{{Cite magazine |last=Zetter |first=Kim |date=17 May 2005 |title=Tor Torches Online Tracking |magazine=Wired |url=http://archive.wired.com/politics/security/news/2005/05/67542?currentPage=all |access-date=30 August 2014 |archive-date=26 July 2014 |archive-url=https://web.archive.org/web/20140726025108/http://archive.wired.com/politics/security/news/2005/05/67542?currentPage=all |url-status=live }} Tor has, for example, been used by criminal enterprises, hacktivism groups, and law enforcement agencies at cross purposes, sometimes simultaneously; likewise, agencies within the U.S. government variously fund Tor (the U.S. State Department, the National Science Foundation, and – through the Broadcasting Board of Governors, which itself partially funded Tor until October 2012 – Radio Free Asia) and seek to subvert it. Tor was one of a dozen circumvention tools evaluated by a Freedom House-funded report based on user experience from China in 2010, which include Ultrasurf, Hotspot Shield, and Freegate.{{Cite web |title=Leaping Over the Firewall: A Review of Censorship Circumvention Tools |url=https://freedomhouse.org/sites/default/files/2020-02/Archived_Special_Report_FH_Censorship_Circumvention_tools.pdf |access-date=December 30, 2023 |website=freedomhouse.org|archive-url=https://web.archive.org/web/20231228031624/https://freedomhouse.org/sites/default/files/2020-02/Archived_Special_Report_FH_Censorship_Circumvention_tools.pdf|archive-date=28 December 2023}}

Tor is not meant to completely solve the issue of anonymity on the web. Tor is not designed to completely erase tracking but instead to reduce the likelihood for sites to trace actions and data back to the user.{{cite web |title=Tor: Overview |url=https://www.torproject.org/about/overview.html.en |website=The Tor Project |access-date=29 April 2015 |archive-date=6 June 2015 |archive-url=https://web.archive.org/web/20150606002957/https://www.torproject.org/about/overview.html.en |url-status=live }}

Tor is also used for illegal activities. These can include privacy protection or censorship circumvention, as well as distribution of child abuse content, drug sales, or malware distribution.{{Cite journal |last1=Jardine |first1=Eric |last2=Lindner |first2=Andrew M. |last3=Owenson |first3=Gareth |date=2020-12-15 |title=The potential harms of the Tor anonymity network cluster disproportionately in free countries |journal=Proceedings of the National Academy of Sciences |language=en |volume=117 |issue=50 |pages=31716–31721 |doi=10.1073/pnas.2011893117 |issn=0027-8424 |pmid=33257555 |pmc=7749358 |bibcode=2020PNAS..11731716J |doi-access=free }}

Tor has been described by The Economist, in relation to Bitcoin and Silk Road, as being "a dark corner of the web". It has been targeted by the American National Security Agency and the British GCHQ signals intelligence agencies, albeit with marginal success, and more successfully by the British National Crime Agency in its Operation Notarise.{{cite web |last1=Boiten |first1=Eerke |last2=Hernandez-Castro |first2=Julio |date=28 July 2014 |title=Can you really be identified on Tor or is that just what the cops want you to believe? |url=http://phys.org/news/2014-07-tor-cops.html |website=Phys.org |access-date=31 July 2014 |archive-date=1 February 2019 |archive-url=https://web.archive.org/web/20190201224220/https://phys.org/news/2014-07-tor-cops.html |url-status=live }} At the same time, GCHQ has been using a tool named "Shadowcat" for "end-to-end encrypted access to VPS over SSH using the Tor network".{{cite web |date=14 July 2014 |title=JTRIG Tools and Techniques |url=https://firstlook.org/theintercept/document/2014/07/14/jtrig-tools-techniques/ |website=The Intercept |access-date=14 July 2014 |archive-date=14 July 2014 |archive-url=https://web.archive.org/web/20140714224430/https://firstlook.org/theintercept/document/2014/07/14/jtrig-tools-techniques/ |url-status=live }}{{cite web |date=5 July 2012 |title=Document from an internal GCHQ wiki lists tools and techniques developed by the Joint Threat Research Intelligence Group |url=https://www.documentcloud.org/documents/1217406-jtrigall.html#document/p4gz |access-date=30 July 2014 |website=documentcoud.org |archive-date=8 August 2014 |archive-url=https://web.archive.org/web/20140808040612/https://www.documentcloud.org/documents/1217406-jtrigall.html#document/p4gz |url-status=live }} Tor can be used for anonymous defamation, unauthorized news leaks of sensitive information, copyright infringement, distribution of illegal sexual content, selling controlled substances, weapons, and stolen credit card numbers,{{Cite news |last=Steinberg |first=Joseph |date=8 January 2015 |title=How Your Teenage Son or Daughter May Be Buying Heroin Online |work=Forbes |url=https://www.forbes.com/sites/josephsteinberg/2015/01/08/how-your-children-can-buy-illegal-drugs-online/ |access-date=6 February 2015 |archive-date=10 February 2015 |archive-url=https://web.archive.org/web/20150210015157/http://www.forbes.com/sites/josephsteinberg/2015/01/08/how-your-children-can-buy-illegal-drugs-online/ |url-status=live }} money laundering, bank fraud,{{cite web |date=5 December 2014 |title=Treasury Dept: Tor a Big Source of Bank Fraud |url=http://krebsonsecurity.com/2014/12/treasury-dept-tor-a-big-source-of-bank-fraud/ |website=Krebs on Security |access-date=7 December 2014 |archive-date=3 February 2019 |archive-url=https://web.archive.org/web/20190203162229/https://krebsonsecurity.com/2014/12/treasury-dept-tor-a-big-source-of-bank-fraud/ |url-status=live }} credit card fraud, identity theft and the exchange of counterfeit currency;{{cite web |last=Farivar |first=Cyrus |date=3 April 2015 |title=How a $3.85 latte paid for with a fake $100 bill led to counterfeit kingpin's downfall |url=https://arstechnica.com/tech-policy/2015/04/how-a-3-85-latte-paid-for-with-a-fake-100-bill-lead-to-counterfeit-kingpins-downfall/ |access-date=19 April 2015 |website=Ars Technica |archive-date=18 April 2015 |archive-url=https://web.archive.org/web/20150418023540/http://arstechnica.com/tech-policy/2015/04/how-a-3-85-latte-paid-for-with-a-fake-100-bill-lead-to-counterfeit-kingpins-downfall/ |url-status=live }} the black market utilizes the Tor infrastructure, at least in part, in conjunction with Bitcoin. It has also been used to brick IoT devices.{{cite web |last=Cimpanu |first=Catalin |date=6 April 2017 |title=New Malware Intentionally Bricks IoT Devices |url=https://www.bleepingcomputer.com/news/security/new-malware-intentionally-bricks-iot-devices/ |website=BleepingComputer |access-date=7 April 2017 |archive-date=19 February 2019 |archive-url=https://web.archive.org/web/20190219020834/https://www.bleepingcomputer.com/news/security/new-malware-intentionally-bricks-iot-devices/ |url-status=live }}

In its complaint against Ross William Ulbricht of Silk Road, the US Federal Bureau of Investigation acknowledged that Tor has "known legitimate uses". According to CNET, Tor's anonymity function is "endorsed by the Electronic Frontier Foundation (EFF) and other civil liberties groups as a method for whistleblowers and human rights workers to communicate with journalists". EFF's Surveillance Self-Defense guide includes a description of where Tor fits in a larger strategy for protecting privacy and anonymity.

In 2014, the EFF's Eva Galperin told Businessweek that "Tor's biggest problem is press. No one hears about that time someone wasn't stalked by their abuser. They hear how somebody got away with downloading child porn."

The Tor Project states that Tor users include "normal people" who wish to keep their Internet activities private from websites and advertisers, people concerned about cyber-spying, and users who are evading censorship such as activists, journalists, and military professionals. In November 2013, Tor had about four million users.{{Cite news |last=Dredge |first=Stuart |date=5 November 2013 |title=What is Tor? A beginner's guide to the privacy tool |work=The Guardian |url=https://www.theguardian.com/technology/2013/nov/05/tor-beginners-guide-nsa-browser |access-date=30 August 2014 |archive-date=15 August 2014 |archive-url=https://web.archive.org/web/20140815233728/http://www.theguardian.com/technology/2013/nov/05/tor-beginners-guide-nsa-browser |url-status=live }} According to the Wall Street Journal, in 2012 about 14% of Tor's traffic connected from the United States, with people in "Internet-censoring countries" as its second-largest user base.{{Cite news |last=Fowler |first=Geoffrey A. |date=17 December 2012 |title=Tor: An Anonymous, And Controversial, Way to Web-Surf |work=The Wall Street Journal |url=https://online.wsj.com/news/articles/SB10001424127887324677204578185382377144280 |access-date=30 August 2014 |archive-date=19 February 2014 |archive-url=https://web.archive.org/web/20140219235003/http://online.wsj.com/news/articles/SB10001424127887324677204578185382377144280 |url-status=live }} Tor is increasingly used by victims of domestic violence and the social workers and agencies that assist them, even though shelter workers may or may not have had professional training on cyber-security matters.{{cite web |last=Tveten |first=Julianne |date=12 April 2017 |title=Where Domestic Violence and Cybersecurity Intersect |url=https://rewire.news/article/2017/04/12/domestic-violence-cybersecurity-intersect/ |access-date=9 August 2017 |website=Rewire |archive-date=10 August 2017 |archive-url=https://web.archive.org/web/20170810052253/https://rewire.news/article/2017/04/12/domestic-violence-cybersecurity-intersect/ |url-status=live }} Properly deployed, however, it precludes digital stalking, which has increased due to the prevalence of digital media in contemporary online life. Along with SecureDrop, Tor is used by news organizations such as The Guardian, The New Yorker, ProPublica and The Intercept to protect the privacy of whistleblowers.{{Cite news |last=Ellis |first=Justin |date=5 June 2014 |title=The Guardian introduces SecureDrop for document leaks |work=Nieman Journalism Lab |url=http://www.niemanlab.org/2014/06/the-guardian-introduces-securedrop-for-document-leaks/ |access-date=30 August 2014 |archive-date=17 August 2014 |archive-url=https://web.archive.org/web/20140817181552/http://www.niemanlab.org/2014/06/the-guardian-introduces-securedrop-for-document-leaks/ |url-status=live }}

In March 2015, the Parliamentary Office of Science and Technology released a briefing which stated that "There is widespread agreement that banning online anonymity systems altogether is not seen as an acceptable policy option in the U.K." and that "Even if it were, there would be technical challenges." The report further noted that Tor "plays only a minor role in the online viewing and distribution of indecent images of children" (due in part to its inherent latency); its usage by the Internet Watch Foundation, the utility of its onion services for whistleblowers, and its circumvention of the Great Firewall of China were touted.{{cite web |last=O'Neill |first=Patrick Howell |date=9 March 2015 |title=U.K. Parliament says banning Tor is unacceptable and impossible |url=http://www.dailydot.com/politics/uk-briefing-tor-child-abuse-minor-role/ |access-date=19 April 2015 |website=The Daily Dot |archive-date=2 April 2015 |archive-url=https://web.archive.org/web/20150402091025/http://www.dailydot.com/politics/uk-briefing-tor-child-abuse-minor-role/ |url-status=live }}

Tor's executive director, Andrew Lewman, also said in August 2014 that agents of the NSA and the GCHQ have anonymously provided Tor with bug reports.{{Cite news |last=Kelion |first=Leo |date=22 August 2014 |title=NSA and GCHQ agents 'leak Tor bugs', alleges developer |work=BBC News |url=https://www.bbc.com/news/technology-28886462 |access-date=21 July 2018 |archive-date=2 February 2019 |archive-url=https://web.archive.org/web/20190202041855/https://www.bbc.com/news/technology-28886462 |url-status=live }}

The Tor Project's FAQ offers supporting reasons for the EFF's endorsement:

{{blockquote|Criminals can already do bad things. Since they're willing to break laws, they already have lots of options available that provide better privacy than Tor provides...

Tor aims to provide protection for ordinary people who want to follow the law. Only criminals have privacy right now, and we need to fix that...

So yes, criminals could in theory use Tor, but they already have better options, and it seems unlikely that taking Tor away from the world will stop them from doing their bad things. At the same time, Tor and other privacy measures can fight identity theft, physical crimes like stalking, and so on.|source=Tor Project FAQ}}

File:Tor Circuit Diagram.svg

Tor aims to conceal its users' identities and their online activity from surveillance and traffic analysis by separating identification and routing. It is an implementation of onion routing, which encrypts and then randomly bounces communications through a network of relays run by volunteers around the globe. These onion routers employ encryption in a multi-layered manner (hence the onion metaphor) to ensure perfect forward secrecy between relays, thereby providing users with anonymity in a network location. That anonymity extends to the hosting of censorship-resistant content by Tor's anonymous onion service feature. Furthermore, by keeping some of the entry relays (bridge relays) secret, users can evade Internet censorship that relies upon blocking public Tor relays.

Because the IP address of the sender and the recipient are not both in cleartext at any hop along the way, anyone eavesdropping at any point along the communication channel cannot directly identify both ends. Furthermore, to the recipient, it appears that the last Tor node (called the exit node), rather than the sender, is the originator of the communication.

A Tor user's SOCKS-aware applications can be configured to direct their network traffic through a Tor instance's SOCKS interface, which is listening on TCP port 9050 (for standalone Tor) or 9150 (for Tor Browser bundle) at localhost.{{cite web |title=TorPCAP – Tor Network Forensics |url=https://www.netresec.com/?page=Blog&month=2018-12&post=TorPCAP---Tor-Network-Forensics |access-date=12 December 2018 |website=Netresec |date = 12 December 2018|archive-date=12 December 2018 |archive-url=https://web.archive.org/web/20181212201750/https://www.netresec.com/?page=Blog&month=2018-12&post=TorPCAP---Tor-Network-Forensics |url-status=live }} Tor periodically creates virtual circuits through the Tor network through which it can multiplex and onion-route that traffic to its destination. Once inside a Tor network, the traffic is sent from router to router along the circuit, ultimately reaching an exit node at which point the cleartext packet is available and is forwarded on to its original destination. Viewed from the destination, the traffic appears to originate at the Tor exit node.

Tor's application independence sets it apart from most other anonymity networks: it works at the Transmission Control Protocol (TCP) stream level. Applications whose traffic is commonly anonymized using Tor include Internet Relay Chat (IRC), instant messaging, and World Wide Web browsing.

{{Anchor|Hidden services}}

{{See also|List of Tor onion services}}

{{Further|Dark web}}

File:Tor Onion Service Diagram.svg.]]

Tor can also provide anonymity to websites and other servers. Servers configured to receive inbound connections only through Tor are called onion services (formerly, hidden services).{{cite journal |last1=Winter |first1=Philipp |last2=Edmundson |first2=Anne |last3=Roberts |first3=Laura M. |last4=Dutkowska-Żuk |first4=Agnieszka |last5=Chetty |first5=Marshini |last6=Feamster |first6=Nick |title=How Do Tor Users Interact With Onion Services? |journal=27th USENIX Security Symposium |date=2018 |pages=411–428 |url=https://www.usenix.org/conference/usenixsecurity18/presentation/winter |access-date=23 September 2024 |language=en}} Rather than revealing a server's IP address (and thus its network location), an onion service is accessed through its onion address, usually via the Tor Browser or some other software designed to use Tor. The Tor network understands these addresses by looking up their corresponding public keys and introduction points from a distributed hash table within the network. It can route data to and from onion services, even those hosted behind firewalls or network address translators (NAT), while preserving the anonymity of both parties. Tor is necessary to access these onion services. Because the connection never leaves the Tor network, and is handled by the Tor application on both ends, the connection is always end-to-end encrypted.

Onion services were first specified in 2003{{cite web |last=Mathewson |first=Nick |title=Add first draft of rendezvous point document |url=https://gitweb.torproject.org/tor.git/commit/?id=3d538f6d702937c23bec33b3bdd62ff9fba9d2a3 |access-date=23 September 2016 |website=Tor Source Code |date=12 June 2003 |archive-date=15 November 2018 |archive-url=https://web.archive.org/web/20181115205018/https://gitweb.torproject.org/tor.git/commit/?id=3d538f6d702937c23bec33b3bdd62ff9fba9d2a3 |url-status=live }} and have been deployed on the Tor network since 2004. They are unlisted by design, and can only be discovered on the network if the onion address is already known,{{cite web |title=Protocol overview |url=https://spec.torproject.org/rend-spec/protocol-overview.html |website=Tor Specifications |publisher=Tor Project |access-date=26 September 2024}} though a number of sites and services do catalog publicly known onion addresses. Popular sources of .onion links include Pastebin, Twitter, Reddit, other Internet forums, and tailored search engines.{{Cite news |last=Koebler |first=Jason |date=23 February 2015 |title=The Closest Thing to a Map of the Dark Net: Pastebin |work=Motherboard |url=http://motherboard.vice.com/read/the-closest-thing-to-a-map-of-the-dark-net-pastebin |access-date=14 July 2015 |archive-date=22 December 2016 |archive-url=https://web.archive.org/web/20161222205738/http://motherboard.vice.com/read/the-closest-thing-to-a-map-of-the-dark-net-pastebin |url-status=live }}

While onion services are often discussed in terms of websites, they can be used for any TCP service, and are commonly used for increased security or easier routing to non-web services, such as secure shell remote login, chat services such as IRC and XMPP, or file sharing. They have also become a popular means of establishing peer-to-peer connections in messaging{{cite web |title=About Ricochet Refresh |url=https://www.ricochetrefresh.net/#about |website=Ricochet Refresh |language=en}}{{cite web |title=Mailbox Properties Client |url=https://code.briarproject.org/briar/briar/-/wikis/Mailbox-Properties-Client |website=briar GitLab |access-date=23 September 2024 |language=en |date=16 May 2022}} and file sharing applications. Web-based onion services can be accessed from a standard web browser without client-side connection to the Tor network using services like Tor2web, which remove client anonymity.{{Cite magazine |last=Zetter |first=Kim |date=12 December 2008 |title=New Service Makes Tor Anonymized Content Available to All |url=https://www.wired.com/threatlevel/2008/12/tor-anonymized/ |magazine=Wired |access-date=22 February 2014 |archive-date=18 March 2014 |archive-url=https://web.archive.org/web/20140318042302/http://www.wired.com/threatlevel/2008/12/tor-anonymized/ |url-status=live }}

Like all software with an attack surface, Tor's protections have limitations, and Tor's implementation or design have been vulnerable to attacks at various points throughout its history.{{cite web |title=TROVE |url=https://gitlab.torproject.org/tpo/core/team/-/wikis/NetworkTeam/TROVE |website=Tor Project Wiki |publisher=Tor Project |access-date=26 September 2024 |language=en}} While most of these limitations and attacks are minor, either being fixed without incident or proving inconsequential, others are more notable.

Tor is designed to provide relatively high performance network anonymity against an attacker with a single vantage point on the connection (e.g., control over one of the three relays, the destination server, or the user's internet service provider). Like all current low-latency anonymity networks, Tor cannot and does not attempt to protect against an attacker performing simultaneous monitoring of traffic at the boundaries of the Tor network—i.e., the traffic entering and exiting the network. While Tor does provide protection against traffic analysis, it cannot prevent traffic confirmation via end-to-end correlation.

There are no documented cases of this limitation being used at scale; as of the 2013 Snowden leaks, law enforcement agencies such as the NSA were unable to perform dragnet surveillance on Tor itself, and relied on attacking other software used in conjunction with Tor, such as vulnerabilities in web browsers.

However, targeted attacks have been able to make use of traffic confirmation on individual Tor users, via police surveillance or investigations confirming that a particular person already under suspicion was sending Tor traffic at the exact times the connections in question occurred.{{cite news |last1=Anderson |first1=Nate |title=Stakeout: how the FBI tracked and busted a Chicago Anon |url=https://arstechnica.com/tech-policy/2012/03/stakeout-how-the-fbi-tracked-and-busted-a-chicago-anon/ |access-date=26 September 2024 |work=Ars Technica |date=7 March 2012 |language=en-us}}{{cite news |title=Failing grade: Alleged Harvard bomb hoaxer needed more than Tor to cover his tracks, experts say |url=https://www.nbcnews.com/technolog/failing-grade-alleged-harvard-bomb-hoaxer-needed-more-tor-cover-2D11767028 |access-date=26 September 2024 |work=NBC News |date=18 December 2013 |language=en}} The relay early traffic confirmation attack also relied on traffic confirmation as part of its mechanism, though on requests for onion service descriptors, rather than traffic to the destination server.

Like many decentralized systems, Tor relies on a consensus mechanism to periodically update its current operating parameters. For Tor, these include network parameters like which nodes are good and bad relays, exits, guards, and how much traffic each can handle. Tor's architecture for deciding the consensus relies on a small number of directory authority nodes voting on current network parameters. Currently, there are nine directory authority nodes, and their health is publicly monitored.{{cite web |url=https://consensus-health.torproject.org/ |title=Consensus health |publisher=Consensus-health.torproject.org |date= |access-date=2024-09-26 |archive-date=12 January 2021 |archive-url=https://web.archive.org/web/20210112221602/https://consensus-health.torproject.org/ |url-status=live }} The IP addresses of the authority nodes are hard coded into each Tor client. The authority nodes vote every hour to update the consensus, and clients download the most recent consensus on startup.{{cite web |title=Getting Started with Tor Development |author=George Tankersley |date=2017-10-04 |url=https://blog.gtank.cc/tor-dev-101/ |access-date=16 January 2021 |archive-date=22 January 2021 |archive-url=https://web.archive.org/web/20210122001011/https://blog.gtank.cc/tor-dev-101/ |url-status=live }}{{cite web |url=https://blog.torproject.org/introducing-bastet-our-new-directory-authority |title=Introducing Bastet, Our New Directory Authority |author=tommy |date=2017-11-02 |publisher=The Tor Project |access-date=16 January 2021 |archive-date=25 November 2020 |archive-url=https://web.archive.org/web/20201125230425/https://blog.torproject.org/introducing-bastet-our-new-directory-authority |url-status=live }}{{cite web |title=10 years of collecting Tor directory data |author=Karsten Loesing |date=2014-05-15 |url=https://blog.torproject.org/10-years-collecting-tor-directory-data |publisher=The Tor Project |access-date=16 January 2021 |archive-date=20 June 2020 |archive-url=https://web.archive.org/web/20200620160219/https://blog.torproject.org/10-years-collecting-tor-directory-data |url-status=live }} A compromise of the majority of the directory authorities could alter the consensus in a way that is beneficial to an attacker. Alternatively, a network congestion attack, such as a DDoS, could theoretically prevent the consensus nodes from communicating, and thus prevent voting to update the consensus (though such an attack would be visible).{{Citation needed|date=April 2022}}

Tor makes no attempt to conceal the IP addresses of exit relays, or hide from a destination server the fact that a user is connecting via Tor.{{cite web |title=You should hide the list of Tor relays, so people can't block the exits. |url=https://support.torproject.org/misc/hide-exits/ |website=Tor Support |publisher=Tor Project}} Operators of Internet sites therefore have the ability to prevent traffic from Tor exit nodes or to offer reduced functionality for Tor users. For example, Wikipedia generally forbids all editing when using Tor or when using an IP address also used by a Tor exit node,{{cite web |title=Wikipedia:Advice to users using Tor |url=https://en.wikipedia.org/wiki/Wikipedia:Advice_to_users_using_Tor |website=Wikipedia |access-date=26 September 2024 |language=en |date=12 November 2022}} and the BBC blocks the IP addresses of all known Tor exit nodes from its iPlayer service.{{cite web |title=BBC iPlayer Help – Why does BBC iPlayer think I'm outside the UK? |url=https://www.bbc.co.uk/iplayer/help/troubleshooting/tv-games-consoles/in_the_uk_message |url-status=dead |archive-url=https://web.archive.org/web/20171228212137/https://www.bbc.co.uk/iplayer/help/troubleshooting/tv-games-consoles/in_the_uk_message |archive-date=28 December 2017 |access-date=10 September 2017 |website=BBC |language=en-GB}}

Apart from intentional restrictions of Tor traffic, Tor use can trigger defense mechanisms on websites intended to block traffic from IP addresses observed to generate malicious or abnormal traffic.{{cite web |title=Tor Browser |url=https://support.torproject.org/tbb/#tbb_website-blocking-tor |website=Support |publisher=Tor Project |access-date=26 September 2024}}{{cite web |last1=Prince |first1=Matthew |title=The Trouble with Tor |url=https://blog.cloudflare.com/the-trouble-with-tor/ |website=The Cloudflare Blog |publisher=Cloudflare |access-date=26 September 2024 |language=en |date=30 March 2016}} Because traffic from all Tor users is shared by a comparatively small number of exit relays, tools can misidentify distinct sessions as originating from the same user, and attribute the actions of a malicious user to a non-malicious user, or observe an unusually large volume of traffic for one IP address. Conversely, a site may observe a single session connecting from different exit relays, with different Internet geolocations, and assume the connection is malicious, or trigger geo-blocking. When these defense mechanisms are triggered, it can result in the site blocking access, or presenting captchas to the user.

{{Anchor |Relay early attack}}

{{Further|CERT Coordination Center#Operation Onymous |Operation Onymous#Tor 0-day exploit}}

In July 2014, the Tor Project issued a security advisory for a "relay early traffic confirmation" attack, disclosing the discovery of a group of relays attempting to de-anonymize onion service users and operators.{{cite web |last=Dingledine |first=Roger |date=30 July 2014 |title=Tor security advisory: "relay early" traffic confirmation attack |url=https://blog.torproject.org/tor-security-advisory-relay-early-traffic-confirmation-attack |publisher=The Tor Project |access-date=9 July 2018 |archive-date=24 May 2019 |archive-url=https://web.archive.org/web/20190524031037/https://blog.torproject.org/tor-security-advisory-relay-early-traffic-confirmation-attack |url-status=live }} A set of onion service directory nodes (i.e., the Tor relays responsible for providing information about onion services) were found to be modifying traffic of requests. The modifications made it so the requesting client's guard relay, if controlled by the same adversary as the onion service directory node, could easily confirm that the traffic was from the same request. This would allow the adversary to simultaneously know the onion service involved in the request, and the IP address of the client requesting it (where the requesting client could be a visitor or owner of the onion service).

The attacking nodes joined the network on 30 January, using a Sybil attack to comprise 6.4% of guard relay capacity, and were removed on 4 July. In addition to removing the attacking relays, the Tor application was patched to prevent the specific traffic modifications that made the attack possible.

In November 2014, there was speculation in the aftermath of Operation Onymous, resulting in 17 arrests internationally, that a Tor weakness had been exploited. A representative of Europol was secretive about the method used, saying: "This is something we want to keep for ourselves. The way we do this, we can't share with the whole world, because we want to do it again and again and again."{{Cite magazine |last=Greenberg |first=Andy |date=7 November 2014 |title=Global Web Crackdown Arrests 17, Seizes Hundreds Of Dark Net Domains |url=https://www.wired.com/2014/11/operation-onymous-dark-web-arrests |magazine=Wired |access-date=9 August 2015 |archive-date=9 August 2015 |archive-url=https://web.archive.org/web/20150809113102/http://www.wired.com/2014/11/operation-onymous-dark-web-arrests/ |url-status=live }}

A BBC source cited a "technical breakthrough"{{Cite news |last=Wakefield |first=Jane |date=7 November 2014 |title=Huge raid to shut down 400-plus dark net sites – |work=BBC News |url=https://www.bbc.co.uk/news/technology-29950946 |access-date=9 August 2015 |archive-date=21 August 2015 |archive-url=https://web.archive.org/web/20150821232538/http://www.bbc.co.uk/news/technology-29950946 |url-status=live }}

that allowed tracking physical locations of servers, and the initial number of infiltrated sites led to the exploit speculation. A Tor Project representative downplayed this possibility, suggesting that execution of more traditional police work was more likely.{{cite web |last=O'Neill |first=Patrick Howell |date=7 November 2014 |title=The truth behind Tor's confidence crisis |website=The Daily Dot |url=http://www.dailydot.com/politics/tor-crisis-of-confidence/ |access-date=10 November 2014 |archive-url=https://web.archive.org/web/20141110122301/http://www.dailydot.com/politics/tor-crisis-of-confidence/ |archive-date=10 November 2014 |url-status=live }}{{cite web |last=Knight |first=Shawn |date=7 November 2014 |title=Operation Onymous seizes hundreds of darknet sites, 17 arrested globally |url=http://www.techspot.com/news/58751-operation-onymous-seizes-hundreds-darknet-sites-17-arrested.html |access-date=8 November 2014 |website=Techspot |archive-date=8 November 2014 |archive-url=https://web.archive.org/web/20141108205443/http://www.techspot.com/news/58751-operation-onymous-seizes-hundreds-darknet-sites-17-arrested.html |url-status=live }}

In November 2015, court documents suggested a connection between the attack and arrests, and raised concerns about security research ethics.{{cite web |date=11 November 2015 |title=Court Docs Show a University Helped FBI Bust Silk Road 2, Child Porn Suspects |url=http://motherboard.vice.com/read/court-docs-show-a-university-helped-fbi-bust-silk-road-2-child-porn-suspects |access-date=20 November 2015 |website=Motherboard |archive-date=21 November 2015 |archive-url=https://web.archive.org/web/20151121155246/http://motherboard.vice.com/read/court-docs-show-a-university-helped-fbi-bust-silk-road-2-child-porn-suspects |url-status=live }}{{cite web |date=11 November 2015 |title=Did the FBI Pay a University to Attack Tor Users? |url=https://blog.torproject.org/blog/did-fbi-pay-university-attack-tor-users |access-date=20 November 2015 |website=torproject.org |archive-date=18 November 2015 |archive-url=https://web.archive.org/web/20151118131446/https://blog.torproject.org/blog/did-fbi-pay-university-attack-tor-users |url-status=live }} The documents revealed that the FBI obtained IP addresses of onion services and their visitors from a "university-based research institute", leading to arrests. Reporting from Motherboard found that the timing and nature of the relay early traffic confirmation attack matched the description in the court documents. Multiple experts, including a senior researcher with the ICSI of UC Berkeley, Edward Felten of Princeton University, and the Tor Project agreed that the CERT Coordination Center of Carnegie Mellon University was the institute in question.{{cite web |last=Felten|first= Ed|date=31 July 2014 |title=Why were CERT researchers attacking Tor? |publisher=Freedom to Tinker, Center for Information Technology Policy, Princeton University |url=https://freedom-to-tinker.com/blog/felten/why-were-cert-researchers-attacking-tor/ |access-date=9 July 2018 |archive-url=https://web.archive.org/web/20160905235550/https://freedom-to-tinker.com/blog/felten/why-were-cert-researchers-attacking-tor/ |archive-date=5 September 2016 |url-status=live }} Concerns raised included the role of an academic institution in policing, sensitive research involving non-consenting users, the non-targeted nature of the attack, and the lack of disclosure about the incident.

Many attacks targeted at Tor users result from flaws in applications used with Tor, either in the application itself, or in how it operates in combination with Tor. E.g., researchers with Inria in 2011 performed an attack on BitTorrent users by attacking clients that established connections both using and not using Tor, then associating other connections shared by the same Tor circuit.

When using Tor, applications may still provide data tied to a device, such as information about screen resolution, installed fonts, language configuration, or supported graphics functionality, reducing the set of users a connection could possibly originate from, or uniquely identifying them.{{cite web |title=Anti-Fingerprinting |url=https://tb-manual.torproject.org/anti-fingerprinting/ |website=Tor Browser Manual |publisher=Tor Project |access-date=26 September 2024}} This information is known as the device fingerprint, or browser fingerprint in the case of web browsers. Applications implemented with Tor in mind, such as Tor Browser, can be designed to minimize the amount of information leaked by the application and reduce its fingerprint.{{cite web |title=What Is Fingerprinting? |url=https://ssd.eff.org/module/what-fingerprinting |website=Surveillance Self-Defense |publisher=Electronic Frontier Foundation |access-date=26 September 2024}}

Tor cannot encrypt the traffic between an exit relay and the destination server.

If an application does not add an additional layer of end-to-end encryption between the client and the server, such as Transport Layer Security (TLS, used in HTTPS) or the Secure Shell (SSH) protocol, this allows the exit relay to capture and modify traffic.{{cite web |title=Tor security advisory: exit relays running sslstrip in May and June 2020 |url=https://blog.torproject.org/bad-exit-relays-may-june-2020/ |website=Tor Blog |publisher=Tor Project |access-date=26 September 2024}}{{cite web |title=Secure Connections |url=https://tb-manual.torproject.org/secure-connections/ |website=Tor Browser Manual |publisher=Tor Project |access-date=26 September 2024}} Attacks from malicious exit relays have recorded usernames and passwords, and modified Bitcoin addresses to redirect transactions.{{cite news |last1=Nichols |first1=Shaun |title=This is node joke. Tor battles to fend off swarm of Bitcoin-stealing evil exit relays making up about 25% of outgoing capacity at its height |url=https://www.theregister.com/2020/08/12/tor_exit_nodes/ |access-date=26 September 2024 |work=The Register |date=12 August 2020}}

Some of these attacks involved actively removing the HTTPS protections that would have otherwise been used. To attempt to prevent this, Tor Browser has since made it so only connections via onion services or HTTPS are allowed by default.{{cite web |title=New Release: Tor Browser 11.5 |url=https://blog.torproject.org/new-release-tor-browser-115/ |website=Tor Blog |publisher=Tor Project |access-date=26 September 2024}}

{{Anchor|EgotisticalGiraffe}}

In 2011, the Dutch authority investigating child pornography discovered the IP address of a Tor onion service site from an unprotected administrator's account and gave it to the FBI, who traced it to Aaron McGrath.{{cite web |title=United States v. McGrath |url=https://www.courtlistener.com/docket/26742968/united-states-v-mcgrath |website=Courtlistener.com |publisher=Free Law Project |access-date=2 March 2024 |language=English |date=12 December 2013}} After a year of surveillance, the FBI launched "Operation Torpedo" which resulted in McGrath's arrest and allowed them to install their Network Investigative Technique (NIT) malware on the servers for retrieving information from the users of the three onion service sites that McGrath controlled.{{Cite magazine |last=Poulsen |first=Kevin |date=8 May 2014 |title=Visit the Wrong Website, and the FBI Could End Up in Your Computer |url=https://www.wired.com/2014/08/operation_torpedo/ |magazine=Wired |access-date=12 March 2017 |archive-date=11 January 2018 |archive-url=https://web.archive.org/web/20180111024650/https://www.wired.com/2014/08/operation_torpedo/ |url-status=live }} The technique exploited a vulnerability in Firefox/Tor Browser that had already been patched, and therefore targeted users that had not updated. A Flash application sent a user's IP address directly back to an FBI server,{{cite web |date=16 July 2015 |title=Feds bust through huge Tor-hidden child porn site using questionable malware |url=https://arstechnica.com/tech-policy/2015/07/feds-bust-through-huge-tor-hidden-child-porn-site-using-questionable-malware/ |website=Ars Technica |access-date=26 July 2018 |archive-date=24 March 2020 |archive-url=https://web.archive.org/web/20200324213851/https://arstechnica.com/tech-policy/2015/07/feds-bust-through-huge-tor-hidden-child-porn-site-using-questionable-malware/ |url-status=live }}{{cite web |title=FBI Tor busting 227 1 |url=https://www.documentcloud.org/documents/2124281-fbi-tor-busting-227-1.html |access-date=26 July 2018 |archive-date=2 July 2018 |archive-url=https://web.archive.org/web/20180702204642/https://www.documentcloud.org/documents/2124281-fbi-tor-busting-227-1.html |url-status=live }}{{Cite journal |last1=Miller |first1=Matthew |last2=Stroschein |first2=Joshua |last3=Podhradsky |first3=Ashley |date=25 May 2016 |title=Reverse Engineering a NIT That Unmasks Tor Users |url=https://commons.erau.edu/adfsl/2016/wednesday/10/ |journal=Annual ADFSL Conference on Digital Forensics, Security and Law |access-date=26 July 2018 |archive-date=2 July 2018 |archive-url=https://web.archive.org/web/20180702204544/https://commons.erau.edu/adfsl/2016/wednesday/10/ |url-status=live }}{{Cite magazine |date=16 December 2014 |title=The FBI Used the Web's Favorite Hacking Tool to Unmask Tor Users |url=https://www.wired.com/2014/12/fbi-metasploit-tor/ |magazine=Wired |access-date=26 July 2018 |archive-date=22 February 2019 |archive-url=https://web.archive.org/web/20190222011924/https://www.wired.com/2014/12/fbi-metasploit-tor/ |url-status=live }} and resulted in revealing at least 25 US users as well as numerous users from other countries.{{Cite magazine |date=27 August 2014 |title=Federal Cybersecurity Director Found Guilty on Child Porn Charges |url=https://www.wired.com/2014/08/federal-cybersecurity-director-guilty-child-porn-charges/ |magazine=Wired |access-date=26 July 2018 |archive-date=23 February 2019 |archive-url=https://web.archive.org/web/20190223085543/https://www.wired.com/2014/08/federal-cybersecurity-director-guilty-child-porn-charges/ |url-status=live }} McGrath was sentenced to 20 years in prison in early 2014, while at least 18 others (including a former Acting HHS Cyber Security Director) were sentenced in subsequent cases.{{cite web |date=5 January 2015 |title=Former Acting HHS Cyber Security Director Sentenced to 25 Years in Prison for Engaging in Child Pornography Enterprise |url=https://www.justice.gov/opa/pr/former-acting-hhs-cyber-security-director-sentenced-25-years-prison-engaging-child |url-status=live |archive-url=https://web.archive.org/web/20180702233127/https://www.justice.gov/opa/pr/former-acting-hhs-cyber-security-director-sentenced-25-years-prison-engaging-child |archive-date=2 July 2018 |publisher=US Department of Justice}}{{cite web |date=17 December 2015 |title=New York Man Sentenced to Six Years in Prison for Receiving and Accessing Child Pornography |url=https://www.justice.gov/opa/pr/new-york-man-sentenced-six-years-prison-receiving-and-accessing-child-pornography |url-status=live |archive-url=https://web.archive.org/web/20180705062657/https://www.justice.gov/opa/pr/new-york-man-sentenced-six-years-prison-receiving-and-accessing-child-pornography |archive-date=5 July 2018 |publisher=US Department of Justice}}

In August 2013, it was discovered{{Cite magazine|last=Poulsen|first=Kevin|date=2013-08-05|title=Feds Are Suspects in New Malware That Attacks Tor Anonymity|magazine=Wired|url=https://www.wired.com/2013/08/freedom-hosting/|access-date=12 March 2017|archive-date=29 April 2014|archive-url=https://web.archive.org/web/20140429202100/http://www.wired.com/2013/08/freedom-hosting/|url-status=live}}{{cite web|last=Krebs|first=Brian|date=2013-08-13|title=Firefox Zero-Day Used in Child Porn Hunt?|url=https://krebsonsecurity.com/2013/08/firefox-zero-day-used-in-child-porn-hunt/|access-date=2020-12-26|website=Krebs on Security|archive-date=13 December 2020|archive-url=https://web.archive.org/web/20201213180903/https://krebsonsecurity.com/2013/08/firefox-zero-day-used-in-child-porn-hunt/|url-status=live}} that the Firefox browsers in many older versions of the Tor Browser Bundle were vulnerable to a JavaScript-deployed shellcode attack, as NoScript was not enabled by default. Attackers used this vulnerability to extract users' MAC and IP addresses and Windows computer names. News reports linked this to a FBI operation targeting Freedom Hosting's owner, Eric Eoin Marques, who was arrested on a provisional extradition warrant issued by a United States' court on 29 July.{{Cite news|last=O'Faolain|first=Aodhan|date=2013-08-08|title=Man sought in US on child porn charges further remanded in custody|newspaper=The Irish Times|url=https://www.irishtimes.com/news/ireland/irish-news/man-sought-in-us-on-child-porn-charges-further-remanded-in-custody-1.1488624|access-date=2020-12-26|archive-date=9 August 2013|archive-url=https://web.archive.org/web/20130809222019/http://www.irishtimes.com/news/ireland/irish-news/man-sought-in-us-on-child-porn-charges-further-remanded-in-custody-1.1488624|url-status=live}} The FBI extradited Marques from Ireland to the state of Maryland on 4 charges: distributing; conspiring to distribute; and advertising child pornography, as well as aiding and abetting advertising of child pornography.[https://www.theguardian.com/us-news/2021/sep/16/man-behind-worlds-biggest-source-of-child-abuse-imagery-is-jailed-for-27-years Man behind world's biggest source of child abuse imagery is jailed for 27 years] {{Webarchive|url=https://web.archive.org/web/20211005095259/https://www.theguardian.com/us-news/2021/sep/16/man-behind-worlds-biggest-source-of-child-abuse-imagery-is-jailed-for-27-years |date=5 October 2021 }}, the guardian.com, 2021/09/16 The FBI acknowledged the attack in a 12 September 2013 court filing in Dublin; further technical details from a training presentation leaked by Edward Snowden revealed the code name for the exploit as "EgotisticalGiraffe".

In 2022, Kaspersky researchers found that when looking up "Tor Browser" in Chinese on YouTube, one of the URLs provided under the top-ranked Chinese-language video actually pointed to malware disguised as Tor Browser. Once installed, it saved browsing history and form data that genuine Tor forgot by default, and downloaded malicious components if the device's IP addresses was in China. Kaspersky researchers noted that the malware was not stealing data to sell for profit, but was designed to identify users.{{Cite web|url= https://www.theverge.com/2022/10/4/23386979/tor-malware-chinese-youtube-anonymity-vpn-kaspersky|title= Someone is tricking Chinese YouTube users with a spyware version of the Tor Browser|work= The Verge|date= 2022-10-04|access-date= 18 October 2022|archive-date= 18 October 2022|archive-url= https://web.archive.org/web/20221018162609/https://www.theverge.com/2022/10/4/23386979/tor-malware-chinese-youtube-anonymity-vpn-kaspersky|url-status= live}}

Like client applications that use Tor, servers relying on onion services for protection can introduce their own weaknesses. Servers that are reachable through Tor onion services and the public Internet can be subject to correlation attacks, and all onion services are susceptible to misconfigured services (e.g., identifying information included by default in web server error responses), leaking uptime and downtime statistics, intersection attacks, or various user errors. The OnionScan program, written by independent security researcher Sarah Jamie Lewis, comprehensively examines onion services for such flaws and vulnerabilities.{{cite web |last=Cox |first=Joseph |date=6 April 2016 |title=A Tool to Check If Your Dark Web Site Really Is Anonymous: 'OnionScan' will probe dark web sites for security weaknesses |url=https://motherboard.vice.com/en_us/article/kb7bg3/onionscan-checks-if-your-dark-web-site-really-is-anonymous |access-date=7 July 2017 |website=Motherboard |archive-date=16 August 2017 |archive-url=https://web.archive.org/web/20170816012653/https://motherboard.vice.com/en_us/article/kb7bg3/onionscan-checks-if-your-dark-web-site-really-is-anonymous |url-status=live }}

{{See also|The Tor Project#Tools|Guardian Project (software)#Projects}}

The main implementation of Tor is written primarily in C.

{{Infobox software

| name = Tor Browser

| screenshot = 250px

| logo = Tor Browser icon (New).png

| logo size = 70px

| caption = Tor Browser showing its start page – about:tor

| developer = Tor Project

| ver layout = stacked

| latest release version = {{Multiple releases

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}}

| latest preview version = {{Multiple releases

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|branch2=Linux

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|branch4=Windows

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}}

| repo = {{URL|https://gitweb.torproject.org/tor-browser.git/}}

| engine = Gecko

| operating system = {{flatlist|

• Windows 10{{cite web|title=Tor Browser Manual: Installation|url=https://tb-manual.torproject.org/installation/|website=torproject.org|access-date=20 January 2025}} and later
• Unix-like (inc. macOS)
• Android}}

| size = {{Nowrap|90–165 MB}}

| language = 37 languages{{cite web|url=https://www.torproject.org/download/languages/|title=Download Tor Browser in your language|publisher=The Tor Project, Inc.|access-date=19 Dec 2022|archive-date=3 June 2021|archive-url=https://web.archive.org/web/20210603225308/https://www.torproject.org/download/languages/|url-status=live}}

| genre = Onion routing, anonymity, web browser, feed reader

| license = Mozilla Public License{{cite web|title=Tor Project: FAQ |url=https://torproject.org/docs/faq.html.en |website=torproject.org |access-date=31 October 2019 |archive-date=24 March 2019 |archive-url=https://web.archive.org/web/20190324153623/https://www.torproject.org/docs/faq.html.en |url-status=live}}

| website = {{URL|torproject.org}}

}}

The Tor Browser{{cite web |date=23 June 2014 |title=Tor Browser Bundle |url=https://www.torproject.org/projects/torbrowser.html.en |archive-url=https://web.archive.org/web/20140623203436/https://www.torproject.org/projects/torbrowser.html.en |archive-date=23 June 2014 |access-date=21 May 2017 |website=Tor Project}} is a web browser capable of accessing the Tor network. It was created as the Tor Browser Bundle by Steven J. Murdoch and announced in January 2008.{{Cite mailing list |last=Murdoch |first=Steven J. |author-link=Steven J. Murdoch |date=30 January 2008 |title=New Tor distribution for testing: Tor Browser Bundle |mailing-list=tor-talk |url=https://lists.torproject.org/pipermail/tor-talk/2008-January/007837.html |access-date=13 January 2020 |archive-date=5 March 2020 |archive-url=https://web.archive.org/web/20200305015731/https://lists.torproject.org/pipermail/tor-talk/2008-January/007837.html |url-status=live }} The Tor Browser consists of a modified Mozilla Firefox ESR web browser, the TorButton, TorLauncher, NoScript and the Tor proxy. Users can run the Tor Browser from removable media. It can operate under Microsoft Windows, macOS, Android and Linux.

The default search engine is DuckDuckGo (until version 4.5, Startpage.com was its default). The Tor Browser automatically starts Tor background processes and routes traffic through the Tor network. Upon termination of a session the browser deletes privacy-sensitive data such as HTTP cookies and the browsing history. This is effective in reducing web tracking and canvas fingerprinting, and it also helps to prevent creation of a filter bubble.{{citation needed|date=April 2022}}

To allow download from places where accessing the Tor Project URL may be risky or blocked, a GitHub repository is maintained with links for releases hosted in other domains.{{cite web |date=23 September 2020 |title=This repository contains TorBrowser Releases. |website=GitHub |url=https://github.com/TheTorProject/gettorbrowser |access-date=23 September 2020 |archive-date=23 September 2020 |archive-url=https://web.archive.org/web/20200923155534/https://github.com/TheTorProject/gettorbrowser |url-status=live }}

{{Infobox software

| name = Tor Messenger

| logo = 128px

| logo alt =

| screenshot =

| caption =

| author =

| developer = The Tor Project

| released = {{Start date and age|2015|10|29|df=yes}}{{cite web |last=Singh |first=Sukhbir |date=29 October 2015 |title=Tor Messenger Beta: Chat over Tor, Easily |url=https://blog.torproject.org/blog/tor-messenger-beta-chat-over-tor-easily |access-date=31 October 2015 |website=The Tor Blog |publisher=The Tor Project |archive-date=30 October 2015 |archive-url=https://web.archive.org/web/20151030223028/https://blog.torproject.org/blog/tor-messenger-beta-chat-over-tor-easily |url-status=live }}

| discontinued = yes

| latest release version = 0.5.0-beta-1

| latest release date = {{Start date and age|2017|09|28|df=yes}}{{cite web |last=Singh |first=Sukhbir |date=28 September 2017 |title=Tor Messenger 0.5.0b1 is released |url=https://blog.torproject.org/tor-messenger-050b1-released |access-date=6 October 2017 |website=sukhbir's blog |publisher=The Tor Project |archive-date=6 October 2017 |archive-url=https://web.archive.org/web/20171006112837/https://blog.torproject.org/tor-messenger-050b1-released |url-status=live }}{{cite web |last=Singh |first=Sukhbir |date=2 April 2018 |title=Sunsetting Tor Messenger |url=https://blog.torproject.org/sunsetting-tor-messenger |access-date=9 April 2020 |archive-date=2 April 2020 |archive-url=https://web.archive.org/web/20200402233906/https://blog.torproject.org/sunsetting-tor-messenger |url-status=live }}

| repo = https://gitweb.torproject.org/tor-messenger-build.git

| programming language = C/C++, JavaScript, CSS, XUL

| operating system = {{flatlist|

• Windows XP and later
• Unix-like (inc. macOS)}}

| size =

| language = English

| genre =

| license =

| website = {{URL|https://trac.torproject.org/projects/tor/wiki/doc/TorMessenger}}

}}

On 29 October 2015, the Tor Project released Tor Messenger Beta, an instant messaging program based on Instantbird with Tor and OTR built in and used by default. Like Pidgin and Adium, Tor Messenger supports multiple different instant messaging protocols; however, it accomplishes this without relying on libpurple, implementing all chat protocols in the memory-safe language JavaScript instead.{{cite web |date=13 July 2015 |title=Tor Messenger Design Document |url=https://trac.torproject.org/projects/tor/wiki/doc/TorMessenger/DesignDoc |access-date=22 November 2015 |website=The Tor Project |archive-date=22 November 2015 |archive-url=https://web.archive.org/web/20151122170840/https://trac.torproject.org/projects/tor/wiki/doc/TorMessenger/DesignDoc |url-status=live }}{{cite web |title=Sunsetting Tor Messenger {{!}} Tor Project |url=https://blog.torproject.org/sunsetting-tor-messenger/ |access-date=2022-05-07 |website=blog.torproject.org |archive-date=22 April 2022 |archive-url=https://web.archive.org/web/20220422231716/https://blog.torproject.org/sunsetting-tor-messenger/ |url-status=live }}

According to Lucian Armasu of Toms Hardware, in April 2018, the Tor Project shut down the Tor Messenger project for three reasons: the developers of "Instabird" {{sic}} discontinued support for their own software, limited resources and known metadata problems.{{cite web |last=Aemasu |first=Lucian |date=3 April 2018 |title=Tor Project Shuts Down Development Of Tor Messenger |url=http://www.tomshardware.com/news/tor-project-ends-tor-messenger,36811.html |access-date=3 April 2018 |website=Tom's Hardware |language=en}} The Tor Messenger developers explained that overcoming any vulnerabilities discovered in the future would be impossible due to the project relying on outdated software dependencies.{{cite web |last=Sharwood |first=Simon |date=3 April 2018 |title=Tor 'sunsets' secure Messenger that never exited beta |url=https://www.theregister.co.uk/2018/04/03/tor_messenger_sunset/ |url-status=live |archive-url=https://web.archive.org/web/20180715115016/https://www.theregister.co.uk/2018/04/03/tor_messenger_sunset/ |archive-date=15 July 2018 |access-date=2 October 2019 |website=The Register |language=en}}

In 2016, Tor developer Mike Perry announced a prototype tor-enabled smartphone based on CopperheadOS.{{Cite web |title=Tor Mobile {{!}} Tor Project {{!}} Support |url=https://support.torproject.org/tormobile/ |access-date=2021-02-14 |website=support.torproject.org}}{{Cite web |date=2014-10-08 |title=How to anonymize all of your apps on Android |url=https://www.dailydot.com/debug/anonymous-android-apps-orbot-orwall-orweb/ |access-date=2021-02-14 |website=The Daily Dot |language=en-US}} It was meant as a direction for Tor on mobile.{{Cite web |last=Staff |first=Ars |date=2016-11-22 |title=Tor phone is antidote to Google "hostility" over Android, says developer |url=https://arstechnica.com/information-technology/2016/11/tor-phone-prototype-google-hostility-android-open-source/ |access-date=2021-02-14 |website=Ars Technica |language=en-us}} The project was called 'Mission Improbable'. Copperhead's then lead developer Daniel Micay welcomed the prototype.{{Cite web |last=Staff |first=Ars |date=2016-11-22 |title=Tor phone is antidote to Google "hostility" over Android, says developer |url=https://arstechnica.com/information-technology/2016/11/tor-phone-prototype-google-hostility-android-open-source/ |url-status=live |archive-url=https://web.archive.org/web/20220813072819/https://arstechnica.com/information-technology/2016/11/tor-phone-prototype-google-hostility-android-open-source/ |archive-date=13 August 2022 |access-date=2022-08-13 |website=Ars Technica |language=en-us}}

The Vuze (formerly Azureus) BitTorrent client, Bitmessage anonymous messaging system, and TorChat instant messenger include Tor support. The Briar messenger routes all messaging via Tor by default. OnionShare allows users to share files using Tor.{{cite book |last1=Hassan |first1=Nihad |last2=Hijazi |first2=Rami |title=Data Hiding Techniques in Windows OS: A Practical Approach to Investigation and Defense |year=2016 |publisher=Syngress |isbn=978-0-12-804496-4 |page=184 |url=https://books.google.com/books?id=sy2lCgAAQBAJ&pg=PA184 |access-date=5 July 2022 |archive-date=5 July 2022 |archive-url=https://web.archive.org/web/20220705191255/https://books.google.com/books?id=sy2lCgAAQBAJ&pg=PA184 |url-status=live }}

The Guardian Project is actively developing a free and open-source suite of applications and firmware for the Android operating system to improve the security of mobile communications. The applications include the ChatSecure instant messaging client, Orbot Tor implementation (also available for iOS),{{Citation |title=Orbot iOS |date=2022-08-25 |url=https://github.com/guardianproject/orbot-ios |publisher=Guardian Project |access-date=2022-08-25 |archive-date=25 August 2022 |archive-url=https://web.archive.org/web/20220825200802/https://github.com/guardianproject/orbot-ios |url-status=live }} Orweb (discontinued) privacy-enhanced mobile browser,{{cite web |last=n8fr8 |date=30 June 2015 |title=Orfox: Aspiring to bring Tor Browser to Android |url=https://guardianproject.info/2015/06/30/orfox-aspiring-to-bring-tor-browser-to-android/ |access-date=17 August 2015 |website=guardianproject.info |quote=Our plan is to actively encourage users to move from Orweb to Orfox, and stop active development of Orweb, even removing to from the Google Play Store. |archive-date=13 September 2015 |archive-url=https://web.archive.org/web/20150913130030/https://guardianproject.info/2015/06/30/orfox-aspiring-to-bring-tor-browser-to-android/ |url-status=live }} Orfox, the mobile counterpart of the Tor Browser, ProxyMob Firefox add-on, and ObscuraCam.

Onion Browser[https://mtigas/OnionBrowser/blob/2.X/LICENSE Endless / Onion Browser License (OBL)]{{Dead link|date=March 2023 |bot=InternetArchiveBot |fix-attempted=yes }} is open-source, privacy-enhancing web browser for iOS, which uses Tor.{{cite web |title=Tor at the Heart: Onion Browser (and more iOS Tor) |publisher=The Tor Blog |url=https://blog.torproject.org/blog/tor-heart-onion-browser-and-more-ios-tor |format= |access-date= |last= |date= |year= |language= |pages= |archive-date=28 August 2017 |archive-url=https://web.archive.org/web/20170828041621/https://blog.torproject.org/blog/tor-heart-onion-browser-and-more-ios-tor |url-status=live }} It is available in the iOS App Store,{{Cite web|url=https://apps.apple.com/en/app/onion-browser/id519296448|title=Onion Browser on the App Store}} and source code is available on GitHub.{{cite web|title=OnionBrowser/OnionBrowser|periodical=GitHub|url=https://github.com/OnionBrowser/OnionBrowser|format=|access-date=|last=|date=2021-06-30|language=en|pages=|archive-date=17 November 2021|archive-url=https://web.archive.org/web/20211117151444/https://github.com/OnionBrowser/OnionBrowser|url-status=live}}

Brave added support for Tor in its desktop browser's private-browsing mode.{{cite web|last=Shankland|first=Stephen|title=Brave advances browser privacy with Tor-powered tabs|url=https://www.cnet.com/news/brave-advances-browser-privacy-with-tor-powered-tabs/|publisher=CNET|date=28 June 2018|access-date=27 September 2018|archive-date=27 September 2018|archive-url=https://web.archive.org/web/20180927204204/https://www.cnet.com/news/brave-advances-browser-privacy-with-tor-powered-tabs/|url-status=live}}{{cite web|last=Brave|date=2020-10-05|title=Brave.com now has its own Tor Onion Service, providing more users with secure access to Brave|url=https://brave.com/new-onion-service/|access-date=2021-01-22|website=Brave Browser|archive-date=6 October 2020|archive-url=https://web.archive.org/web/20201006004823/https://brave.com/new-onion-service/|url-status=live}}

File:Orbot-logo.svg|Orbot logo

File:Orbot, running under Samsung Internet.png|Orbot 16.6.3, running under Samsung Internet

File:Onion Browser on iPad.png|Onion Browser on iPad

In September of 2024, it was announced that Tails, a security-focused operating system, had become part of the Tor Project.{{cite news |last1=Sawers |first1=Paul |title=The Tor Project merges with Tails, a Linux-based portable OS focused on privacy |url=https://techcrunch.com/2024/09/26/the-tor-project-merges-with-tails-a-linux-based-portable-os-focused-on-privacy/ |access-date=26 September 2024 |work=TechCrunch |date=26 September 2024}} Other security-focused operating systems that make or made extensive use of Tor include Hardened Linux From Scratch, Incognito, Liberté Linux, Qubes OS, Subgraph, Parrot OS, Tor-ramdisk, and Whonix.

File:TorPluggable transports-animation.webm

Tor has been praised for providing privacy and anonymity to vulnerable Internet users such as political activists fearing surveillance and arrest, ordinary web users seeking to circumvent censorship, and people who have been threatened with violence or abuse by stalkers.{{Cite news |last=Brandom |first=Russell |date=9 May 2014 |title=Domestic violence survivors turn to Tor to escape abusers |work=The Verge |url=https://www.theverge.com/2014/5/9/5699600/domestic-violence-survivors-turn-to-tor-to-escape-abusers |access-date=30 August 2014 |archive-date=2 September 2014 |archive-url=https://web.archive.org/web/20140902093440/http://www.theverge.com/2014/5/9/5699600/domestic-violence-survivors-turn-to-tor-to-escape-abusers |url-status=live }}{{Cite news |last=Gurnow |first=Michael |date=1 July 2014 |title=Seated Between Pablo Escobar and Mahatma Gandhi: The Sticky Ethics of Anonymity Networks |work=Dissident Voice |url=http://dissidentvoice.org/2013/06/seated-between-pablo-escobar-and-mahatma-gandhi/ |access-date=17 July 2014 |archive-date=6 October 2014 |archive-url=https://web.archive.org/web/20141006101844/http://dissidentvoice.org/2013/06/seated-between-pablo-escobar-and-mahatma-gandhi/ |url-status=live }} The U.S. National Security Agency (NSA) has called Tor "the king of high-secure, low-latency Internet anonymity", and BusinessWeek magazine has described it as "perhaps the most effective means of defeating the online surveillance efforts of intelligence agencies around the world". Other media have described Tor as "a sophisticated privacy tool",{{Cite magazine |last=Zetter |first=Kim |date=1 June 2010 |title=WikiLeaks Was Launched With Documents Intercepted From Tor |magazine=Wired |url=https://www.wired.com/2010/06/wikileaks-documents/ |access-date=30 August 2014 |archive-date=12 August 2014 |archive-url=https://web.archive.org/web/20140812114104/http://www.wired.com/2010/06/wikileaks-documents/ |url-status=live }} "easy to use"{{Cite news |last=Lee |first=Timothy B. |date=10 June 2013 |title=Five ways to stop the NSA from spying on you |newspaper=The Washington Post |url=https://www.washingtonpost.com/blogs/wonkblog/wp/2013/06/10/five-ways-to-stop-the-nsa-from-spying-on-you/ |access-date=30 August 2014 |archive-date=4 October 2014 |archive-url=https://web.archive.org/web/20141004072624/http://www.washingtonpost.com/blogs/wonkblog/wp/2013/06/10/five-ways-to-stop-the-nsa-from-spying-on-you/ |url-status=live }} and "so secure that even the world's most sophisticated electronic spies haven't figured out how to crack it".{{Cite news |last1=Harris |first1=Shane |last2=Hudson |first2=John |date=4 October 2014 |title=Not Even the NSA Can Crack the State Department's Favorite Anonymous Service |work=Foreign Policy |url=http://thecable.foreignpolicy.com/posts/2013/10/04/not_even_the_nsa_can_crack_the_state_departments_online_anonymity_tool |access-date=30 August 2014 |archive-date=20 July 2014 |archive-url=https://web.archive.org/web/20140720045913/http://thecable.foreignpolicy.com/posts/2013/10/04/not_even_the_nsa_can_crack_the_state_departments_online_anonymity_tool |url-status=live }}

Advocates for Tor say it supports freedom of expression, including in countries where the Internet is censored, by protecting the privacy and anonymity of users. The mathematical underpinnings of Tor lead it to be characterized as acting "like a piece of infrastructure, and governments naturally fall into paying for infrastructure they want to use".{{cite web |last=Norton |first=Quinn |date=9 December 2014 |title=Clearing the air around Tor |url=http://pando.com/2014/12/09/clearing-the-air-around-tor/ |website=PandoDaily |access-date=10 December 2014 |archive-date=25 May 2019 |archive-url=https://web.archive.org/web/20190525115617/https://pando.com/2014/12/09/clearing-the-air-around-tor/ |url-status=live }}

The project was originally developed on behalf of the U.S. intelligence community and continues to receive U.S. government funding, and has been criticized as "more resembl[ing] a spook project than a tool designed by a culture that values accountability or transparency".{{Cite news|last=Levine|first=Yasha|date=16 July 2014|title=Almost everyone involved in developing Tor was (or is) funded by the US government|work=Pando Daily|url=http://pando.com/2014/07/16/tor-spooks/|url-status=live|access-date=21 April 2016|archive-url=https://web.archive.org/web/20160411185901/https://pando.com/2014/07/16/tor-spooks/|archive-date=11 April 2016}} {{as of|2012}}, 80% of The Tor Project's $2M annual budget came from the United States government, with the U.S. State Department, the Broadcasting Board of Governors, and the National Science Foundation as major contributors, aiming "to aid democracy advocates in authoritarian states".{{Cite news|date=3 July 2014|title=NSA targets the privacy-conscious|work=Panorama|publisher=Norddeutscher Rundfunk|url=http://daserste.ndr.de/panorama/aktuell/nsa230_page-1.html|url-status=live|access-date=4 July 2014|archive-url=https://web.archive.org/web/20140703215350/http://daserste.ndr.de/panorama/aktuell/nsa230_page-1.html|archive-date=3 July 2014|vauthors=Appelbaum J, Gibson A, Goetz J, Kabisch V, Kampf L, Ryge L}} Other public sources of funding include DARPA, the U.S. Naval Research Laboratory, and the Government of Sweden. Some have proposed that the government values Tor's commitment to free speech, and uses the darknet to gather intelligence.Moore, Daniel; Rid, Thomas. "Cryptopolitik and the Darknet". Survival. Feb2016, Vol. 58 Issue 1, p7-38. 32p.{{Request quotation | date=July 2018}} Tor also receives funding from NGOs including Human Rights Watch, and private sponsors including Reddit and Google.Inc., The Tor Project,. "Tor: Sponsors". www.torproject.org. Retrieved 28 October 2016. Dingledine said that the United States Department of Defense funds are more similar to a research grant than a procurement contract. Tor executive director Andrew Lewman said that even though it accepts funds from the U.S. federal government, the Tor service did not collaborate with the NSA to reveal identities of users.

Critics say that Tor is not as secure as it claims,{{Cite news |date=2 September 2013 |title=Tor is Not as Safe as You May Think |work=Infosecurity magazine |url=http://www.infosecurity-magazine.com/news/tor-is-not-as-safe-as-you-may-think/ |access-date=30 August 2014 |archive-date=27 August 2014 |archive-url=https://web.archive.org/web/20140827203552/http://www.infosecurity-magazine.com/news/tor-is-not-as-safe-as-you-may-think/ |url-status=live }} pointing to U.S. law enforcement's investigations and shutdowns of Tor-using sites such as web-hosting company Freedom Hosting and online marketplace Silk Road. In October 2013, after analyzing documents leaked by Edward Snowden, The Guardian reported that the NSA had repeatedly tried to crack Tor and had failed to break its core security, although it had had some success attacking the computers of individual Tor users. The Guardian also published a 2012 NSA classified slide deck, entitled "Tor Stinks", which said: "We will never be able to de-anonymize all Tor users all the time", but "with manual analysis we can de-anonymize a very small fraction of Tor users".{{Cite news |date=4 October 2014 |title='Tor Stinks' presentation – read the full document |work=The Guardian |url=https://www.theguardian.com/world/interactive/2013/oct/04/tor-stinks-nsa-presentation-document |access-date=30 August 2014 |archive-date=29 August 2014 |archive-url=https://web.archive.org/web/20140829193451/http://www.theguardian.com/world/interactive/2013/oct/04/tor-stinks-nsa-presentation-document |url-status=live }} When Tor users are arrested, it is typically due to human error, not to the core technology being hacked or cracked.{{cite web |last=O'Neill |first=Patrick Howell |date=2 October 2014 |title=The real chink in Tor's armor |url=http://www.dailydot.com/crime/silk-road-tor-arrests/ |website=The Daily Dot |access-date=3 October 2014 |archive-date=25 May 2019 |archive-url=https://web.archive.org/web/20190525124144/https://www.dailydot.com/crime/silk-road-tor-arrests/ |url-status=live }} On 7 November 2014, for example, a joint operation by the FBI, ICE Homeland Security investigations and European Law enforcement agencies led to 17 arrests and the seizure of 27 sites containing 400 pages.{{Dubious | reason=The operation is so successful most likely because of Tor's protocol weakness. Not a good example. (See "Relay early traffic confirmation attack" above.) |date=July 2018}} A late 2014 report by Der Spiegel using a new cache of Snowden leaks revealed, however, that {{as of|2012|lc=y}} the NSA deemed Tor on its own as a "major threat" to its mission, and when used in conjunction with other privacy tools such as OTR, Cspace, ZRTP, RedPhone, Tails, and TrueCrypt was ranked as "catastrophic," leading to a "near-total loss/lack of insight to target communications, presence..."

In March 2011, The Tor Project received the Free Software Foundation's 2010 Award for Projects of Social Benefit. The citation read, "Using free software, Tor has enabled roughly 36 million people around the world to experience freedom of access and expression on the Internet while keeping them in control of their privacy and anonymity. Its network has proved pivotal in dissident movements in both Iran and more recently Egypt."

Iran tried to block Tor at least twice in 2011. One attempt simply blocked all servers with 2-hour-expiry security certificates; it was successful for less than 24 hours.{{cite web |last1=Lambert |first1=Patrick |title=How the TOR Project defeated Iran filters inside 24 hours |url=https://www.techrepublic.com/article/how-the-tor-project-defeated-iran-filters-inside-24-hours/ |website=TechRepublic |date=21 September 2011 |access-date=15 October 2022 |archive-date=15 October 2022 |archive-url=https://web.archive.org/web/20221015202425/https://www.techrepublic.com/article/how-the-tor-project-defeated-iran-filters-inside-24-hours/ |url-status=live }}{{cite web |title=Iranian block on Tor traffic quickly foiled – The H Security: News and Features |url=http://www.h-online.com/security/news/item/Iranian-block-on-Tor-traffic-quickly-foiled-1344762.html |website=www.h-online.com |access-date=15 October 2022 |archive-date=18 October 2022 |archive-url=https://web.archive.org/web/20221018042001/http://www.h-online.com/security/news/item/Iranian-block-on-Tor-traffic-quickly-foiled-1344762.html |url-status=live }}

In 2012, Foreign Policy magazine named Dingledine, Mathewson, and Syverson among its Top 100 Global Thinkers "for making the web safe for whistleblowers".

In 2013, Jacob Appelbaum described Tor as a "part of an ecosystem of software that helps people regain and reclaim their autonomy. It helps to enable people to have agency of all kinds; it helps others to help each other and it helps you to help yourself. It runs, it is open and it is supported by a large community spread across all walks of life."

In June 2013, whistleblower Edward Snowden used Tor to send information about PRISM to The Washington Post and The Guardian.

In 2014, the Russian government offered a $111,000 contract to "study the possibility of obtaining technical information about users and users' equipment on the Tor anonymous network".

In September 2014, in response to reports that Comcast had been discouraging customers from using the Tor Browser, Comcast issued a public statement that "We have no policy against Tor, or any other browser or software."{{cite web |url=https://corporate.comcast.com/comcast-voices/setting-the-record-straight-on-tor |title=Setting the Record Straight on Tor |first=Jason |last=Livingood |date=2014-09-15 |quote=The report may have generated a lot of clicks but is totally inaccurate. Comcast is not asking customers to stop using Tor, or any other browser for that matter. We have no policy against Tor, or any other browser or software. Customers are free to use their Xfinity Internet service to visit any website, use any app, and so forth. ... Comcast doesn't monitor our customer's browser software, web surfing or online history. |access-date=5 January 2021 |archive-date=4 January 2021 |archive-url=https://web.archive.org/web/20210104165011/https://corporate.comcast.com/comcast-voices/setting-the-record-straight-on-tor |url-status=live }}

In October 2014, The Tor Project hired the public relations firm Thomson Communications to improve its public image (particularly regarding the terms "Dark Net" and "hidden services," which are widely viewed as being problematic) and to educate journalists about the technical aspects of Tor.{{cite web |last=O'Neill |first=Patrick Howell |date=26 March 2015 |title=Tor's great rebranding |url=http://www.dailydot.com/politics/tor-media-public-relations-perception/ |access-date=19 April 2015 |website=The Daily Dot |archive-date=12 April 2015 |archive-url=https://web.archive.org/web/20150412172355/http://www.dailydot.com/politics/tor-media-public-relations-perception/ |url-status=live }}

Turkey blocked downloads of Tor Browser from the Tor Project.{{cite web |last1=Galperin |first1=Eva |title=When Is a Tor Block Not a Tor Block? |url=https://www.eff.org/deeplinks/2014/03/when-tor-block-not-tor-block |website=Electronic Frontier Foundation |language=en |date=27 March 2014 |access-date=15 October 2022 |archive-date=15 October 2022 |archive-url=https://web.archive.org/web/20221015225028/https://www.eff.org/deeplinks/2014/03/when-tor-block-not-tor-block |url-status=live }}

In June 2015, the special rapporteur from the United Nations' Office of the High Commissioner for Human Rights specifically mentioned Tor in the context of the debate in the U.S. about allowing so-called backdoors in encryption programs for law enforcement purposes{{Cite news |last=Peterson |first=Andrea |date=28 May 2015 |title=U.N. report: Encryption is important to human rights — and backdoors undermine it |url=https://www.washingtonpost.com/blogs/the-switch/wp/2015/05/28/un-report-encryption-is-important-to-human-rights-and-backdoors-undermine-it |newspaper=The Washington Post |access-date=17 September 2017 |archive-date=23 June 2015 |archive-url=https://web.archive.org/web/20150623030700/http://www.washingtonpost.com/blogs/the-switch/wp/2015/05/28/un-report-encryption-is-important-to-human-rights-and-backdoors-undermine-it/ |url-status=live }} in an interview for The Washington Post.

In July 2015, the Tor Project announced an alliance with the Library Freedom Project to establish exit nodes in public libraries.{{cite web |title=Tor Exit Nodes in Libraries – Pilot (phase one) |url=https://blog.torproject.org/blog/tor-exit-nodes-libraries-pilot-phase-one |access-date=15 September 2015 |website=Tor Project.org |archive-date=8 September 2015 |archive-url=https://web.archive.org/web/20150908012811/https://blog.torproject.org/blog/tor-exit-nodes-libraries-pilot-phase-one |url-status=live }}{{cite web |title=Library Freedom Project |url=https://libraryfreedomproject.org/ |access-date=15 September 2015 |website=libraryfreedomproject.org |archive-date=19 September 2015 |archive-url=https://web.archive.org/web/20150919100044/https://libraryfreedomproject.org/ |url-status=live }} The pilot program, which established a middle relay running on the excess bandwidth afforded by the Kilton Library in Lebanon, New Hampshire, making it the first library in the U.S. to host a Tor node, was briefly put on hold when the local city manager and deputy sheriff voiced concerns over the cost of defending search warrants for information passed through the Tor exit node. Although the Department of Homeland Security (DHS) had alerted New Hampshire authorities to the fact that Tor is sometimes used by criminals, the Lebanon Deputy Police Chief and the Deputy City Manager averred that no pressure to strong-arm the library was applied, and the service was re-established on 15 September 2015.{{cite web |last=Doyle-Burr |first=Nora |date=16 September 2015 |title=Despite Law Enforcement Concerns, Lebanon Board Will Reactivate Privacy Network Tor at Kilton Library |url=http://www.vnews.com/photos/inthenews/18620952-95/despite-law-enforcement-concerns-lebanon-board-will-reactivate-privacy-network-tor-at-kilton-library |url-status=dead |archive-url=https://web.archive.org/web/20150918031540/http://www.vnews.com/photos/inthenews/18620952-95/despite-law-enforcement-concerns-lebanon-board-will-reactivate-privacy-network-tor-at-kilton-library |archive-date=18 September 2015 |access-date=20 November 2015 |website=Valley News}} U.S. Rep. Zoe Lofgren (D-Calif) released a letter on 10 December 2015, in which she asked the DHS to clarify its procedures, stating that "While the Kilton Public Library's board ultimately voted to restore their Tor relay, I am no less disturbed by the possibility that DHS employees are pressuring or persuading public and private entities to discontinue or degrade services that protect the privacy and anonymity of U.S. citizens."{{cite web |date=10 December 2015 |title=Lofgren questions DHS policy towards Tor Relays |url=https://lofgren.house.gov/news/documentsingle.aspx?DocumentID=398038 |url-status=dead |archive-url=https://web.archive.org/web/20160603144959/https://lofgren.house.gov/news/documentsingle.aspx?DocumentID=398038 |archive-date=3 June 2016 |access-date=4 June 2016 |website=house.gov}}{{cite web |last=Geller |first=Eric |date=11 December 2015 |title=Democratic lawmaker wants to know if DHS is sabotaging plans for Tor exit relays |url=http://www.dailydot.com/politics/tor-libraries-dhs-zoe-lofgren-letter/ |access-date=4 June 2016 |website=The Daily Dot |archive-date=10 June 2016 |archive-url=https://web.archive.org/web/20160610194930/http://www.dailydot.com/politics/tor-libraries-dhs-zoe-lofgren-letter/ |url-status=live }}{{cite web |last=Kopfstein |first=Janus |date=12 December 2015 |title=Congresswoman Asks Feds Why They Pressured a Library to Disable Its Tor Node |url=https://motherboard.vice.com/read/congresswoman-asks-feds-why-they-pressured-a-library-to-disable-its-tor-node |url-status=live |archive-url=https://web.archive.org/web/20151222171028/http://motherboard.vice.com/read/congresswoman-asks-feds-why-they-pressured-a-library-to-disable-its-tor-node |archive-date=22 December 2015 |website=Motherboard}} In a 2016 interview, Kilton Library IT Manager Chuck McAndrew stressed the importance of getting libraries involved with Tor: "Librarians have always cared deeply about protecting privacy, intellectual freedom, and access to information (the freedom to read). Surveillance has a very well-documented chilling effect on intellectual freedom. It is the job of librarians to remove barriers to information."{{Cite news |date=4 August 2016 |title=Tor crusader discuss privacy, freedom with ExpressVPN |language=en-US |work=Home of internet privacy |url=https://www.expressvpn.com/blog/chuck-mcandrew-defends-tor/ |access-date=11 September 2017 |archive-date=31 August 2017 |archive-url=https://web.archive.org/web/20170831090756/https://www.expressvpn.com/blog/chuck-mcandrew-defends-tor/ |url-status=live }} The second library to host a Tor node was the Las Naves Public Library in Valencia, Spain, implemented in the first months of 2016.{{Cite news |last=Gonzalo |first=Marilín |date=26 January 2016 |title=Esta biblioteca valenciana es la segunda del mundo en unirse al proyecto Tor |language=es |work=El Diario |url=http://www.eldiario.es/cultura/tecnologia/privacidad/biblioteca-Valencia-primera-Unidos-Tor_0_476303147.html |access-date=4 March 2016 |archive-date=7 March 2016 |archive-url=https://web.archive.org/web/20160307091514/http://www.eldiario.es/cultura/tecnologia/privacidad/biblioteca-Valencia-primera-Unidos-Tor_0_476303147.html |url-status=live }}

In August 2015, an IBM security research group, called "X-Force", put out a quarterly report that advised companies to block Tor on security grounds, citing a "steady increase" in attacks from Tor exit nodes as well as botnet traffic.{{cite web |last=Broersma |first=Matthew |date=26 August 2015 |title=IBM Tells Companies To Block Tor Anonymisation Network |url=http://www.techweekeurope.co.uk/security/ibm-companies-tor-175468 |access-date=15 September 2015 |website=TechWeekEurope UK |archive-date=10 September 2015 |archive-url=https://web.archive.org/web/20150910211854/http://www.techweekeurope.co.uk/security/ibm-companies-tor-175468 |url-status=live }}

In September 2015, Luke Millanta created OnionView (now defunct), a web service that plots the location of active Tor relay nodes onto an interactive map of the world. The project's purpose was to detail the network's size and escalating growth rate.{{Cite magazine |last=Greenberg |first=Andy |date=14 September 2015 |title=Mapping How Tor's Anonymity Network Spread Around the World |url=https://www.wired.com/2015/09/mapping-tors-anonymity-network-spread-around-world/ |magazine=Wired |access-date=9 February 2016 |archive-date=3 February 2016 |archive-url=https://web.archive.org/web/20160203154307/http://www.wired.com/2015/09/mapping-tors-anonymity-network-spread-around-world |url-status=live }}

In December 2015, Daniel Ellsberg (of the Pentagon Papers),{{cite web |date=26 December 2015 |title=This is What a Tor Supporter Looks Like: Daniel Ellsberg |url=https://blog.torproject.org/blog/what-tor-supporter-looks-daniel-ellsberg |access-date=4 June 2016 |website=The Tor Blog |archive-date=4 March 2016 |archive-url=https://web.archive.org/web/20160304100212/https://blog.torproject.org/blog/what-tor-supporter-looks-daniel-ellsberg |url-status=live }} Cory Doctorow (of Boing Boing),{{cite web |date=18 December 2015 |title=This is What a Tor Supporter Looks Like: Cory Doctorow |url=https://blog.torproject.org/blog/what-tor-supporter-looks-cory-doctorow |access-date=4 June 2016 |website=The Tor Blog |archive-date=16 June 2016 |archive-url=https://web.archive.org/web/20160616210816/https://blog.torproject.org/blog/what-tor-supporter-looks-cory-doctorow |url-status=live }} Edward Snowden,{{cite web |date=30 December 2015 |title=This is What a Tor Supporter Looks Like: Edward Snowden |url=https://blog.torproject.org/blog/what-tor-supporter-looks-edward-snowden |access-date=4 June 2016 |website=The Tor Blog |archive-date=9 April 2016 |archive-url=https://web.archive.org/web/20160409024736/https://blog.torproject.org/blog/what-tor-supporter-looks-edward-snowden |url-status=live }} and artist-activist Molly Crabapple,{{cite web |date=9 December 2015 |title=This is what a Tor Supporter looks like: Molly Crabapple |url=https://blog.torproject.org/blog/what-tor-supporter-looks-molly-crabapple |access-date=4 June 2016 |website=The Tor Blog |archive-date=16 June 2016 |archive-url=https://web.archive.org/web/20160616210748/https://blog.torproject.org/blog/what-tor-supporter-looks-molly-crabapple |url-status=live }} amongst others, announced their support of Tor.

In March 2016, New Hampshire state representative Keith Ammon introduced a bill{{cite web |date=10 March 2016 |title=House Bill 1508: An Act allowing public libraries to run certain privacy software |url=http://www.gencourt.state.nh.us/bill_status/billText.aspx?id=796&txtFormat=html |access-date=4 June 2016 |website=New Hampshire State Government |archive-date=11 April 2017 |archive-url=https://web.archive.org/web/20170411043230/http://www.gencourt.state.nh.us/bill_status/billText.aspx?id=796&txtFormat=html |url-status=live }} allowing public libraries to run privacy software. The bill specifically referenced Tor. The text was crafted with extensive input from Alison Macrina, the director of the Library Freedom Project.{{cite web |last=O'Neill |first=Patrick Howell |date=18 February 2016 |title=New Hampshire bill allows for libraries' usage of encryption and privacy software |url=http://www.dailydot.com/politics/new-hampshire-tor-library-legislation/ |access-date=10 March 2016 |website=The Daily Dot |archive-date=11 March 2016 |archive-url=https://web.archive.org/web/20160311073326/http://www.dailydot.com/politics/new-hampshire-tor-library-legislation/ |url-status=live }} The bill was passed by the House 268–62.{{cite web |title=New Hampshire HB1508 – 2016 – Regular Session |url=https://legiscan.com/NH/text/HB1508/id/1288060 |access-date=4 June 2016 |website=legiscan.com |archive-date=29 July 2016 |archive-url=https://web.archive.org/web/20160729171429/https://legiscan.com/NH/text/HB1508/id/1288060 |url-status=live }}

Also in March 2016, the first Tor node, specifically a middle relay, was established at a library in Canada, the Graduate Resource Centre (GRC) in the Faculty of Information and Media Studies (FIMS) at the University of Western Ontario.{{cite web |date=14 March 2016 |title=Library in FIMS joins global network fighting back against digital surveillance, censorship, and the obstruction of information |url=http://www.fims.uwo.ca/news/2016/library_in_fims_joins_global_network_fighting_back_against_digital_surveillance_censorship_and_the_obstruction_of_information.html |access-date=16 March 2016 |website=FIMS News |archive-date=20 March 2016 |archive-url=https://web.archive.org/web/20160320112332/http://www.fims.uwo.ca/news/2016/library_in_fims_joins_global_network_fighting_back_against_digital_surveillance_censorship_and_the_obstruction_of_information.html |url-status=live }} Given that the running of a Tor exit node is an unsettled area of Canadian law,{{cite web |last=Pearson |first=Jordan |date=25 September 2015 |title=Can You Be Arrested for Running a Tor Exit Node In Canada? |url=https://motherboard.vice.com/read/can-you-be-arrested-for-running-a-tor-exit-node-in-canada |access-date=16 March 2016 |website=Motherboard |archive-date=23 March 2016 |archive-url=https://web.archive.org/web/20160323231601/https://motherboard.vice.com/read/can-you-be-arrested-for-running-a-tor-exit-node-in-canada |url-status=live }} and that in general institutions are more capable than individuals to cope with legal pressures, Alison Macrina of the Library Freedom Project has opined that in some ways she would like to see intelligence agencies and law enforcement attempt to intervene in the event that an exit node were established.{{cite web |last=Pearson |first=Jordan |date=16 March 2016 |title=Canadian Librarians Must Be Ready to Fight the Feds on Running a Tor Node |url=https://motherboard.vice.com/en_ca/read/canadian-librarians-must-be-ready-to-fight-the-feds-on-running-a-tor-node-western-library-freedom-project |access-date=16 March 2016 |website=Motherboard |archive-date=19 March 2016 |archive-url=https://web.archive.org/web/20160319083936/http://motherboard.vice.com/en_ca/read/canadian-librarians-must-be-ready-to-fight-the-feds-on-running-a-tor-node-western-library-freedom-project |url-status=live }}

On 16 May 2016, CNN reported on the case of core Tor developer "isis agora lovecruft",{{cite web |url=https://twitter.com/isislovecruft/status/1258515495851921408 |last=lovecruft |first=isis agora |title=May 7, 2020 Tweet |date=2020-05-07 |quote=my name is isis agora lovecruft not Isis Agora Lovecruft |access-date=7 April 2021 |archive-date=27 May 2021 |archive-url=https://web.archive.org/web/20210527215141/https://twitter.com/isislovecruft/status/1258515495851921408 |url-status=live }} who had fled to Germany under the threat of a subpoena by the FBI during the Thanksgiving break of the previous year. The Electronic Frontier Foundation legally represented lovecruft.{{cite web |last=Pagliery |first=Jose |date=17 May 2016 |title=Developer of anonymous Tor software dodges FBI, leaves US |url=https://money.cnn.com/2016/05/17/technology/tor-developer-fbi/index.html |access-date=17 May 2016 |website=CNN |archive-date=17 May 2016 |archive-url=https://web.archive.org/web/20160517153400/http://money.cnn.com/2016/05/17/technology/tor-developer-fbi/index.html |url-status=live }}

On 2 December 2016, The New Yorker reported on burgeoning digital privacy and security workshops in the San Francisco Bay Area, particularly at the hackerspace Noisebridge, in the wake of the 2016 United States presidential election; downloading the Tor browser was mentioned.{{Cite magazine |last=Weiner |first=Anna |date=2 December 2016 |title=Trump Preparedness: Digital Security 101 |url=https://www.newyorker.com/culture/culture-desk/trump-preparedness-digital-security-101 |magazine=The New Yorker |access-date=20 February 2020 |archive-date=25 October 2020 |archive-url=https://web.archive.org/web/20201025144947/https://www.newyorker.com/culture/culture-desk/trump-preparedness-digital-security-101 |url-status=live }} Also, in December 2016, Turkey has blocked the usage of Tor, together with ten of the most used VPN services in Turkey, which were popular ways of accessing banned social media sites and services.{{cite web |date=19 December 2016 |title=Turkey Partially Blocks Access to Tor and Some VPNs |url=https://www.bleepingcomputer.com/news/government/turkey-partially-blocks-access-to-tor-and-some-vpns/ |access-date=24 September 2017 |archive-date=20 December 2016 |archive-url=https://web.archive.org/web/20161220220147/https://www.bleepingcomputer.com/news/government/turkey-partially-blocks-access-to-tor-and-some-vpns/ |url-status=live }}

Tor (and Bitcoin) was fundamental to the operation of the dark web marketplace AlphaBay, which was taken down in an international law enforcement operation in July 2017.{{cite web |date=20 July 2017 |title=Forfeiture Complaint |url=https://www.justice.gov/opa/press-release/file/982821/download |publisher=Justice.gov |page=27 |access-date=28 July 2017 |archive-date=23 September 2020 |archive-url=https://web.archive.org/web/20200923012828/https://www.justice.gov/opa/press-release/file/982821/download |url-status=live }} Despite federal claims that Tor would not shield a user, however,{{cite web |last=Leyden |first=John |date=20 July 2017 |title=Cops harpoon two dark net whales in megabust: AlphaBay and Hansa : Tor won't shield you, warn Feds |url=https://www.theregister.co.uk/2017/07/20/dark_net_megabust/ |access-date=21 July 2017 |website=The Register |archive-date=23 May 2020 |archive-url=https://web.archive.org/web/20200523085637/https://www.theregister.co.uk/2017/07/20/dark_net_megabust/ |url-status=live }} elementary operational security errors outside of the ambit of the Tor network led to the site's downfall.{{cite web |last=McCarthy |first=Kieren |date=20 July 2017 |title=Alphabay shutdown: Bad boys, bad boys, what you gonna do? Not use your Hotmail... ...or the Feds will get you ♪ |url=https://www.theregister.co.uk/2017/07/20/alphabay_hotmail_fbi/ |access-date=21 July 2017 |website=The Register |archive-date=23 May 2020 |archive-url=https://web.archive.org/web/20200523085638/https://www.theregister.co.uk/2017/07/20/alphabay_hotmail_fbi/ |url-status=live }}

In June 2017 the Democratic Socialists of America recommended intermittent Tor usage for politically active organizations and individuals as a defensive mitigation against information security threats.{{cite web |url=https://www.dsausa.org/organize/info_security/ |title=Information Security Memo for Members |date=2017-07-11 |publisher=Democratic Socialists of America |access-date=20 January 2021 |archive-date=20 January 2021 |archive-url=https://web.archive.org/web/20210120104155/https://www.dsausa.org/organize/info_security/ |url-status=live }}{{cite web |url=https://www.dsausa.org/files/2017/07/DSAInformationSecurityRecommendations_June2017.pdf |title=INFORMATION SECURITY RECOMMENDATIONS |date=June 2017 |publisher=Democratic Socialists of America |access-date=20 January 2021 |archive-date=7 September 2020 |archive-url=https://web.archive.org/web/20200907193927/https://www.dsausa.org/files/2017/07/DSAInformationSecurityRecommendations_June2017.pdf |url-status=live }} And in August 2017, according to reportage, cybersecurity firms which specialize in monitoring and researching the dark web (which relies on Tor as its infrastructure) on behalf of banks and retailers routinely share their findings with the FBI and with other law enforcement agencies "when possible and necessary" regarding illegal content. The Russian-speaking underground offering a crime-as-a-service model is regarded as being particularly robust.{{cite web |last=Johnson |first=Tim |date=2 August 2017 |title=Shocked by gruesome crime, cyber execs help FBI on dark web |url=http://www.idahostatesman.com/news/nation-world/national/article164797842.html |website=Idaho Statesman}}

In June 2018, Venezuela blocked access to the Tor network. The block affected both direct connections to the network and connections being made via bridge relays.{{cite web |last=Brandom |first=Russell |date=25 June 2018 |title=Venezuela is blocking access to the Tor network 16 Just days after new web blocks were placed on local media outlets |url=https://www.theverge.com/2018/6/25/17503680/venezuela-tor-blocked-web-censorship |access-date=26 June 2018 |website=The Verge |archive-date=26 June 2018 |archive-url=https://web.archive.org/web/20180626000651/https://www.theverge.com/2018/6/25/17503680/venezuela-tor-blocked-web-censorship |url-status=live }}

On 20 June 2018, Bavarian police raided the homes of the board members of the non-profit Zwiebelfreunde, a member of torservers.net, which handles the European financial transactions of riseup.net in connection with a blog post there which apparently promised violence against the upcoming Alternative for Germany convention.{{cite web |last=Grauer |first=Yael |date=4 July 2018 |title=German police raid homes of Tor-linked group's board members One board member described the police's justification for the raids as a "tenuous" link between the privacy group, a blog, and its email address |url=https://www.zdnet.com/article/german-police-raid-homes-of-tor-linked-groups-board-members/ |access-date=6 July 2018 |website=ZDNet |archive-date=6 July 2018 |archive-url=https://web.archive.org/web/20180706000125/https://www.zdnet.com/article/german-police-raid-homes-of-tor-linked-groups-board-members/ |url-status=live }}{{cite web |last=n/a |first=46halbe |date=4 July 2018 |title=Police searches homes of "Zwiebelfreunde" board members as well as "OpenLab" in Augsburg |url=https://www.ccc.de/en/updates/2018/hausdurchsuchungen-bei-vereinsvorstanden-der-zwiebelfreunde-und-im-openlab-augsburg |access-date=6 July 2018 |website=Chaos Computer Club |archive-date=4 July 2018 |archive-url=https://web.archive.org/web/20180704101613/https://www.ccc.de/en/updates/2018/hausdurchsuchungen-bei-vereinsvorstanden-der-zwiebelfreunde-und-im-openlab-augsburg |url-status=live }} Tor came out strongly against the raid on its support organization, which provides legal and financial aid for the setting up and maintenance of high-speed relays and exit nodes.{{cite web |last=Stelle |first=Sharon |date=5 July 2018 |title=In Support of Torservers |url=https://blog.torproject.org/support-torservers |access-date=6 July 2018 |website=TorProject.org |archive-date=7 July 2018 |archive-url=https://web.archive.org/web/20180707042439/https://blog.torproject.org/support-torservers |url-status=live }} According to torservers.net, on 23 August 2018 the German court at Landgericht München ruled that the raid and seizures were illegal. The hardware and documentation seized had been kept under seal, and purportedly were neither analyzed nor evaluated by the Bavarian police.{{cite web |date=24 August 2018 |title=Gericht urteilt: Durchsuchung bei Zwiebelfreunden war rechtswidrig [Update] |url=https://netzpolitik.org/2018/gericht-urteilt-durchsuchung-bei-zwiebelfreunden-war-rechtswidrig/ |access-date=1 December 2019 |archive-date=12 October 2019 |archive-url=https://web.archive.org/web/20191012011235/https://netzpolitik.org/2018/gericht-urteilt-durchsuchung-bei-zwiebelfreunden-war-rechtswidrig/ |url-status=live }}{{cite web |title=LG München I: Hausdurchsuchungen bei Verein Zwiebelfreunde waren rechtswidrig |url=https://rsw.beck.de/aktuell/meldung/lg-muenchen-i-hausdurchsuchungen-bei-netzaktivisten-rechtswidrig |website=Aktuell |access-date=1 December 2019 |archive-date=15 February 2021 |archive-url=https://web.archive.org/web/20210215083404/https://rsw.beck.de/aktuell/daily/meldung/detail/lg-muenchen-i-hausdurchsuchungen-bei-netzaktivisten-rechtswidrig |url-status=live }}

Since October 2018, Chinese online communities within Tor have begun to dwindle due to increased efforts to stop them by the Chinese government.{{cite web |year=2018 |title=China's clampdown on Tor pushes its hackers into foreign backyards |website=The Register |url=https://www.theregister.co.uk/2018/10/10/russia_china_hacker_forum_comparison |access-date=10 October 2018 |archive-date=10 October 2018 |archive-url=https://web.archive.org/web/20181010184728/https://www.theregister.co.uk/2018/10/10/russia_china_hacker_forum_comparison/ |url-status=live }}

In November 2019, Edward Snowden called for a full, unabridged simplified Chinese translation of his autobiography, Permanent Record, as the Chinese publisher had violated their agreement by expurgating all mentions of Tor and other matters deemed politically sensitive by the Chinese Communist Party.{{cite web |last=Stegner |first=Isabella |date=12 November 2019 |title=Edward Snowden blew the whistle on how Chinese censors scrubbed his book |url=https://qz.com/1746780/edward-snowden-calls-out-chinese-censorship-of-his-book/ |url-status=live |archive-url=https://web.archive.org/web/20191115103544/https://qz.com/1746780/edward-snowden-calls-out-chinese-censorship-of-his-book/ |archive-date=15 November 2019 |access-date=12 November 2019 |website=Quartz}}{{cite web |last=Snowden |first=Edward |date=11 November 2019 |title=The Chinese edition of my new book, #PermanentRecord, has just been censored. |url=https://twitter.com/Snowden/status/1194092273170038784 |url-status=live |archive-url=https://web.archive.org/web/20191112032031/https://twitter.com/Snowden/status/1194092273170038784 |archive-date=12 November 2019 |access-date=8 December 2019 |website=Twitter (@Snowden) |language=en }}

On 8 December 2021, the Russian government agency Roskomnadzor announced it has banned Tor and six VPN services for failing to abide by the Russian Internet blacklist.{{cite web|date=2021-12-08|title=Russia Bans More VPN Products and TOR – December 8, 2021|url=https://dailynewsbrief.com/2021/12/08/russia-bans-more-vpn-products-and-tor/|access-date=2021-12-11|website=Daily NewsBrief|language=en-US|archive-date=8 December 2021|archive-url=https://web.archive.org/web/20211208161518/https://dailynewsbrief.com/2021/12/08/russia-bans-more-vpn-products-and-tor/|url-status=live}} Russian ISPs unsuccessfully attempted to block Tor's main website as well as several bridges beginning on 1 December 2021.{{cite web |title=Russia Ratchets up Internet Control by Blocking Privacy Service Tor |url=https://www.usnews.com/news/technology/articles/2021-12-08/russia-ratchets-up-internet-crackdown-with-block-of-privacy-service-tor |website=U.S. News & World Report |access-date=8 December 2021 |language=en |archive-date=8 December 2021 |archive-url=https://web.archive.org/web/20211208181755/https://www.usnews.com/news/technology/articles/2021-12-08/russia-ratchets-up-internet-crackdown-with-block-of-privacy-service-tor |url-status=live }} The Tor Project has appealed to Russian courts over this ban.{{cite web |title=Tor Project appeals Russian court's decision to block access to Tor |url=https://www.bleepingcomputer.com/news/security/tor-project-appeals-russian-courts-decision-to-block-access-to-tor/ |access-date=2022-03-08 |website=BleepingComputer |language=en-us |archive-date=8 March 2022 |archive-url=https://web.archive.org/web/20220308021038/https://www.bleepingcomputer.com/news/security/tor-project-appeals-russian-courts-decision-to-block-access-to-tor/ |url-status=live }}

In response to Internet censorship during the Russian invasion of Ukraine, the BBC and VOA have directed Russian audiences to Tor.{{cite web |url=https://www.wsj.com/articles/russia-rolls-down-internet-iron-curtain-but-gaps-remain-11647087321 |title=Russia Rolls Down Internet Iron Curtain, but Gaps Remain |work=The Wall Street Journal |last1=Schechner |first1=Sam |last2=Hagey |first2=Keach |date=12 March 2022 |access-date=17 March 2022 |archive-date=17 March 2022 |archive-url=https://web.archive.org/web/20220317075321/https://www.wsj.com/articles/russia-rolls-down-internet-iron-curtain-but-gaps-remain-11647087321 |url-status=live }} The Russian government increased efforts to block access to Tor through technical and political means, while the network reported an increase in traffic from Russia, and increased Russian use of its anti-censorship Snowflake tool.{{cite magazine |url=https://www.wired.com/story/tor-browser-russia-blocks/ |title=How Tor Is Fighting—and Beating—Russian Censorship |first=Matt |last=Burgess |magazine=WIRED |date=July 28, 2022 |access-date=2022-07-30 |archive-date=8 August 2022 |archive-url=https://web.archive.org/web/20220808043854/https://www.wired.com/story/tor-browser-russia-blocks/ |url-status=live }}

Russian courts temporarily lifted the blockade on Tor's website (but not connections to relays) on May 24, 2022{{cite web |title=Russian court lifts block on Tor Project – for now |url=https://www.techradar.com/news/russian-court-lifts-block-on-tor-project-for-now |access-date=2022-12-29 |website=TechRadar |date=24 May 2022 |language=en-us |archive-date=30 December 2022 |archive-url=https://web.archive.org/web/20221230055129/https://www.techradar.com/news/russian-court-lifts-block-on-tor-project-for-now |url-status=live }} due to Russian law requiring that the Tor Project be involved in the case. However, the blockade was reinstated on July 21, 2022.{{cite web |title=Tor GitLab – [Russia] Some ISPs are blocking Tor |url=https://gitlab.torproject.org/tpo/community/support/-/issues/40050 |access-date=2022-12-29 |website=TechRadar |date=2 December 2021 |language=en-us |archive-date=30 December 2022 |archive-url=https://web.archive.org/web/20221230055138/https://gitlab.torproject.org/tpo/community/support/-/issues/40050 |url-status=live }}

Iran implemented rolling internet blackouts during the Mahsa Amini protests, and Tor and Snowflake were used to circumvent them.{{cite news |last1=Browne |first1=Ryan |title=VPN use skyrockets in Iran as citizens navigate internet censorship under Tehran's crackdown |url=https://www.cnbc.com/2022/10/07/vpn-use-skyrockets-in-iran-as-citizens-navigate-internet-censorship.html |work=CNBC |language=en |access-date=11 October 2022 |archive-date=10 October 2022 |archive-url=https://web.archive.org/web/20221010185748/https://www.cnbc.com/2022/10/07/vpn-use-skyrockets-in-iran-as-citizens-navigate-internet-censorship.html |url-status=live }}{{cite news |last1=Küchemann |first1=Fridtjof |title=Per Snowflake ins TOR-Netzwerk: Online-Gasse für Menschen in Iran |url=https://www.faz.net/aktuell/feuilleton/medien/zugang-fuer-iraner-per-snowflake-ins-tor-netzwerk-18346679.html |work=Frankfurter Allgemeine Zeitung |date=September 27, 2022 |language=de |access-date=11 October 2022 |archive-date=10 October 2022 |archive-url=https://web.archive.org/web/20221010215912/https://www.faz.net/aktuell/feuilleton/medien/zugang-fuer-iraner-per-snowflake-ins-tor-netzwerk-18346679.html |url-status=live }}{{cite news |last1=Schwarzer |first1=Matthias |title=Netzsperre im Iran umgehen: Wie "Snowflake" einen Weg ins freie Internet ermöglicht – so kann der Westen helfen |url=https://www.rnd.de/digital/netzsperre-im-iran-umgehen-wie-snowflake-einen-weg-ins-freie-internet-ermoeglicht-so-kann-der-westen-SE3LNI5BKNHJHGJJK2UZHWHXRA.html |access-date=10 October 2022 |work=Redaktions Netzwerk Deutschland |publisher=www.rnd.de |date=September 30, 2022 |language=de |archive-date=10 October 2022 |archive-url=https://web.archive.org/web/20221010215914/https://www.rnd.de/digital/netzsperre-im-iran-umgehen-wie-snowflake-einen-weg-ins-freie-internet-ermoeglicht-so-kann-der-westen-SE3LNI5BKNHJHGJJK2UZHWHXRA.html |url-status=live }}{{cite web |last1=Quintin |first1=Cooper |title=Snowflake Makes It Easy For Anyone to Fight Censorship |url=https://www.eff.org/deeplinks/2022/10/snowflake-makes-it-easy-anyone-fight-censorship |website=Electronic Frontier Foundation |language=en |date=4 October 2022 |access-date=11 October 2022 |archive-date=10 October 2022 |archive-url=https://web.archive.org/web/20221010215913/https://www.eff.org/deeplinks/2022/10/snowflake-makes-it-easy-anyone-fight-censorship |url-status=live }}

China, with its highly centralized control of its internet, had effectively blocked Tor.

Tor responded to earlier vulnerabilities listed above by patching them and improving security. In one way or another, human (user) errors can lead to detection. The Tor Project website provides the best practices (instructions) on how to properly use the Tor browser. When improperly used, Tor is not secure. For example, Tor warns its users that not all traffic is protected; only the traffic routed through the Tor browser is protected. Users are also warned to use HTTPS versions of websites, not to torrent with Tor, not to enable browser plugins, not to open documents downloaded through Tor while online, and to use safe bridges.{{cite web |title=The Tor Project | Privacy & Freedom Online |url=https://torproject.org/ |website=torproject.org |access-date=31 October 2019 |archive-date=31 October 2019 |archive-url=https://web.archive.org/web/20191031195458/https://www.torproject.org/ |url-status=live }} Users are also warned that they cannot provide their name or other revealing information in web forums over Tor and stay anonymous at the same time.{{cite web |title=Tor: Overview – Staying anonymous |url=https://www.torproject.org/about/overview.html.en |access-date=21 September 2016 |archive-date=6 June 2015 |archive-url=https://web.archive.org/web/20150606002957/https://www.torproject.org/about/overview.html.en |url-status=live }}

Despite intelligence agencies' claims that 80% of Tor users would be de-anonymized within 6 months in the year 2013,{{cite web |date=31 August 2016 |title=Building a new Tor that can resist next-generation state surveillance |url=https://arstechnica.com/security/2016/08/building-a-new-tor-that-withstands-next-generation-state-surveillance/ |access-date=13 September 2016 |website=arstechnica.com |archive-date=11 September 2016 |archive-url=https://web.archive.org/web/20160911030754/http://arstechnica.com/security/2016/08/building-a-new-tor-that-withstands-next-generation-state-surveillance/ |url-status=live }} that has still not happened. In fact, as late as September 2016, the FBI could not locate, de-anonymize and identify the Tor user who hacked into the email account of a staffer on Hillary Clinton's email server.{{cite web |first1=Elias |last1=Groll |first2=David |last2=Francis |title=FBI: An Account on Clinton's Private Email Server Was Hacked |url=https://foreignpolicy.com/2016/09/02/fbi-an-account-on-clintons-private-email-server-was-hacked/ |access-date=2020-10-28 |website=Foreign Policy |date=2 September 2016 |language=en-US |archive-date=31 October 2020 |archive-url=https://web.archive.org/web/20201031022316/https://foreignpolicy.com/2016/09/02/fbi-an-account-on-clintons-private-email-server-was-hacked/ |url-status=live }}

The best tactic of law enforcement agencies to de-anonymize users appears to remain with Tor-relay adversaries running poisoned nodes, as well as counting on the users themselves using the Tor browser improperly. For example, downloading a video through the Tor browser and then opening the same file on an unprotected hard drive while online can make the users' real IP addresses available to authorities.{{cite web |date=16 August 2016 |title=Aussie cops ran child porn site for months, revealed 30 US IPs |url=https://arstechnica.com/tech-policy/2016/08/aussie-cops-ran-child-porn-site-for-months-revealed-30-us-ips/ |access-date=13 September 2016 |website=arstechnica.com |archive-date=8 September 2016 |archive-url=https://web.archive.org/web/20160908002444/http://arstechnica.com/tech-policy/2016/08/aussie-cops-ran-child-porn-site-for-months-revealed-30-us-ips/ |url-status=live }}

When properly used, odds of being de-anonymized through Tor are said to be extremely low. Tor project's co-founder Nick Mathewson explained that the problem of "Tor-relay adversaries" running poisoned nodes means that a theoretical adversary of this kind is not the network's greatest threat:

{{quotation|"No adversary is truly global, but no adversary needs to be truly global," he says. "Eavesdropping on the entire Internet is a several-billion-dollar problem. Running a few computers to eavesdrop on a lot of traffic, a selective denial of service attack to drive traffic to your computers, that's like a tens-of-thousands-of-dollars problem." At the most basic level, an attacker who runs two poisoned Tor nodes—one entry, one exit—is able to analyse traffic and thereby identify the tiny, unlucky percentage of users whose circuit happened to cross both of those nodes. In 2016 the Tor network offers a total of around 7,000 relays, around 2,000 guard (entry) nodes and around 1,000 exit nodes. So the odds of such an event happening are one in two million ({{Frac|1|2000}} × {{Frac|1|1000}}), give or take."}}

Tor does not provide protection against end-to-end timing attacks: if an attacker can watch the traffic coming out of the target computer, and also the traffic arriving at the target's chosen destination (e.g. a server hosting a .onion site), that attacker can use statistical analysis to discover that they are part of the same circuit.

A similar attack has been used by German authorities to track down users related to Boystown.{{cite web | url=https://www.heise.de/news/Boystown-Ermittlungen-Mit-der-Stoppuhr-auf-Taeterfang-im-Darknet-9885038.html | title=Darknet: Ermittler nutzten Timing-Analyse zur Deanonymisierung von Tor-Nutzern | date=19 September 2024 }}

Depending on individual user needs, Tor browser offers three levels of security located under the Security Level (the small gray shield at the top-right of the screen) icon > Advanced Security Settings. In addition to encrypting the data, including constantly changing an IP address through a virtual circuit comprising successive, randomly selected Tor relays, several other layers of security are at a user's disposal:{{Cite web |last=Ajaz |first=Shigraf |date=2023-01-26 |title=Tor Browser Privacy Setting-How to Setup Properly? |url=https://beencrypted.com/privacy/anonymous-browsing/tor-browser-privacy-setting/ |access-date=2023-02-06 |website=Beencrypted |language=en-US |archive-date=6 February 2023 |archive-url=https://web.archive.org/web/20230206134734/https://beencrypted.com/privacy/anonymous-browsing/tor-browser-privacy-setting/ |url-status=live }}{{Cite web |title=SECURITY SETTINGS {{!}} Tor Project {{!}} Tor Browser Manual |url=https://tb-manual.torproject.org/security-settings/ |access-date=2023-02-06 |website=tb-manual.torproject.org |archive-date=6 February 2023 |archive-url=https://web.archive.org/web/20230206134739/https://tb-manual.torproject.org/security-settings/ |url-status=live }}

At this level, all features from the Tor Browser and other websites are enabled.

This level eliminates website features that are often pernicious to the user. This may cause some sites to lose functionality. JavaScript is disabled on all non-HTTPS sites; some fonts and mathematical symbols are disabled. Also, audio and video (HTML5 media) are click-to-play.

This level only allows website features required for static sites and basic services. These changes affect images, media, and scripts. Javascript is disabled by default on all sites; some fonts, icons, math symbols, and images are disabled; audio and video (HTML5 media) are click-to-play.

In 2023, Tor unveiled a new defense mechanism to safeguard its onion services against denial of service (DoS) attacks. With the release of Tor 0.4.8, this proof-of-work (PoW) defense promises to prioritize legitimate network traffic while deterring malicious attacks.{{Cite web |author= Pavel (Tor blog writer) |date=23 August 2023 |title=Introducing Proof-of-Work Defense for Onion Services |url=https://blog.torproject.org/introducing-proof-of-work-defense-for-onion-services/ }}

{{Div col|colwidth=20em|small=yes}}

• Anonymous P2P
• Anonymous web browsing
• Crypto-anarchism
• Darknet
• Deep web
• Freedom of information
• Freenet
• GNUnet
• I2P
• Internet censorship circumvention
• Internet privacy
• Signal
• Privacy software
• Privoxy
• Proxy server
• Psiphon
• Tor Phone

{{div col end}}

{{Portal bar| Anarchism |Free and open-source software |Freedom of speech |Internet }}

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{{Cite news |last=Schneier |first=Bruce |date=4 October 2013 |title=Attacking Tor: how the NSA targets users' online anonymity |work=The Guardian |url=https://www.theguardian.com/world/2013/oct/04/tor-attacks-nsa-users-online-anonymity |access-date=22 December 2013 |archive-date=7 August 2017 |archive-url=https://web.archive.org/web/20170807074531/https://www.theguardian.com/world/2013/oct/04/tor-attacks-nsa-users-online-anonymity |url-status=live }}

{{Cite news |last1=Ball |first1=James |last2=Schneier |first2=Bruce |last3=Greenwald |first3=Glenn |date=4 October 2013 |title=NSA and GCHQ target Tor network that protects anonymity of web users |work=The Guardian |url=https://www.theguardian.com/world/2013/oct/04/nsa-gchq-attack-tor-network-encryption |url-status=live |access-date=5 October 2013 |archive-url=https://web.archive.org/web/20190228060200/https://www.theguardian.com/world/2013/oct/04/nsa-gchq-attack-tor-network-encryption |archive-date=28 February 2019}}

{{Cite news |date=4 October 2013 |title=Peeling back the layers of Tor with EgotisticalGiraffe |work=The Guardian |url=https://www.theguardian.com/world/interactive/2013/oct/04/egotistical-giraffe-nsa-tor-document |access-date=5 October 2013 |archive-date=5 October 2013 |archive-url=https://web.archive.org/web/20131005030818/http://www.theguardian.com/world/interactive/2013/oct/04/egotistical-giraffe-nsa-tor-document |url-status=live }}

{{cite web |title=About |url=https://guardianproject.info/ |access-date=10 May 2011 |website=The Guardian Project |archive-date=16 April 2011 |archive-url=https://web.archive.org/web/20110416232400/http://guardianproject.info/ |url-status=live }}

{{cite web |title=ChatSecure: Private Messaging |url=https://guardianproject.info/apps/chatsecure/ |access-date=20 September 2014 |website=The Guardian Project |archive-date=24 September 2014 |archive-url=https://web.archive.org/web/20140924064840/https://guardianproject.info/apps/chatsecure/ |url-status=live }}

{{cite web |title=Orbot: Mobile Anonymity + Circumvention |url=https://guardianproject.info/apps/orbot/ |access-date=10 May 2011 |website=The Guardian Project |archive-date=11 May 2011 |archive-url=https://web.archive.org/web/20110511074732/https://guardianproject.info/apps/orbot/ |url-status=live }}

{{cite web |title=Orweb: Privacy Browser |url=https://guardianproject.info/apps/orweb/ |access-date=10 May 2011 |website=The Guardian Project |archive-date=11 May 2011 |archive-url=https://web.archive.org/web/20110511074727/https://guardianproject.info/apps/orweb/ |url-status=dead }}

{{cite web |title=ProxyMob: Firefox Mobile Add-on |url=https://guardianproject.info/apps/proxymob-firefox-add-on/ |access-date=10 May 2011 |website=The Guardian Project |archive-date=11 May 2011 |archive-url=https://web.archive.org/web/20110511074722/https://guardianproject.info/apps/proxymob-firefox-add-on/ |url-status=dead }}

{{cite web |title=Obscura: Secure Smart Camera |url=https://guardianproject.info/apps/obscuracam/ |access-date=19 September 2014 |website=The Guardian Project |archive-date=24 September 2014 |archive-url=https://web.archive.org/web/20140924040527/https://guardianproject.info/apps/obscuracam/ |url-status=live }}

{{cite web |last=Samson |first=Ted |date=5 August 2013 |title=Tor Browser Bundle for Windows users susceptible to info-stealing attack |url=http://www.infoworld.com/t/data-security/tor-browser-bundle-windows-users-susceptible-info-stealing-attack-224157 |access-date=28 April 2014 |website=InfoWorld |archive-date=29 April 2014 |archive-url=https://web.archive.org/web/20140429044651/http://www.infoworld.com/t/data-security/tor-browser-bundle-windows-users-susceptible-info-stealing-attack-224157 |url-status=live }}

{{Cite book |last=Jones |first=Robert |url=https://archive.org/details/internetforensic0000jone/page/133 |title=Internet forensics |publisher=O'Reilly |year=2005 |isbn=978-0-596-10006-3 |page=[https://archive.org/details/internetforensic0000jone/page/133 133]}}

{{cite web |last=Knight |first=John |date=1 September 2011 |title=Tor Browser Bundle-Tor Goes Portable |url=http://www.linuxjournal.com/content/tor-browser-bundle-tor-goes-portable |access-date=28 April 2014 |website=Linux Journal |archive-date=29 April 2014 |archive-url=https://web.archive.org/web/20140429050524/http://www.linuxjournal.com/content/tor-browser-bundle-tor-goes-portable |url-status=live }}

{{Cite news |last=Best |first=Jessica |date=21 January 2014 |title=Man branded 'largest facilitator of child porn on the planet' remanded in custody again |work=Daily Mirror |url=https://www.mirror.co.uk/news/world-news/eric-eoin-marques-man-branded-3046701 |access-date=29 April 2014 |archive-url=https://web.archive.org/web/20140529103734/http://www.mirror.co.uk/news/world-news/eric-eoin-marques-man-branded-3046701 |archive-date=29 May 2014 |url-status=live }}

{{cite web |last=Morisy |first=Michael |date=8 June 2012 |title=Hunting for child porn, FBI stymied by Tor undernet |url=http://www.muckrock.com/news/archives/2012/jun/08/hunting-child-porn-fbi-stymied-tor-undernet/ |access-date=6 August 2012 |website=Muckrock |archive-url=https://web.archive.org/web/20120616185438/http://www.muckrock.com/news/archives/2012/jun/08/hunting-child-porn-fbi-stymied-tor-undernet/ |archive-date=16 June 2012 |url-status=live }}

{{cite web |url=https://www.openhub.net/p/tor |title=Tor |website=Open HUB |access-date=27 May 2021 |archive-date=3 September 2014 |archive-url=https://web.archive.org/web/20140903192951/https://www.openhub.net/p/tor |url-status=live }}

{{cite conference |chapter-url=http://www.onion-router.net/Publications/locating-hidden-servers.pdf |chapter=Locating Hidden Servers |first1=Lasse |last1=Øverlier |first2=Paul |last2=Syverson |title=2006 IEEE Symposium on Security and Privacy (S&P'06) |conference=IEEE Symposium on Security and Privacy |conference-url=http://www.ieee-security.org/TC/SP-Index.html |book-title=Proceedings of the 2006 IEEE Symposium on Security and Privacy |page=1 |publisher=IEEE CS Press |date=21 June 2006 |location=Oakland, Calif. |doi=10.1109/SP.2006.24 |isbn=0-7695-2574-1 |url=http://www.onion-router.net/Publications/locating-hidden-servers.pdf |archive-date=10 August 2013 |archive-url=https://web.archive.org/web/20130810105459/http://www.onion-router.net/Publications/locating-hidden-servers.pdf |url-status=live }}

{{cite web |url=http://www.pcworld.com/article/2458420/russian-government-offers-money-for-identifying-tor-users.html |title=Russian government offers huge reward for help unmasking anonymous Tor users |first=Constantin |last=Lucian |website=PC World |date=25 July 2014 |access-date=26 July 2014 |archive-date=26 July 2014 |archive-url=https://web.archive.org/web/20140726073307/http://www.pcworld.com/article/2458420/russian-government-offers-money-for-identifying-tor-users.html |url-status=live }}

{{cite mailing list |url=http://archives.seul.org/or/dev/Sep-2002/msg00019.html |title=Pre-alpha: run an onion proxy now! |last=Dingledine |first=Roger |mailing-list=or-dev@freehaven.net |date=20 September 2002 |access-date=17 July 2008 |url-status=live |archive-date=26 July 2011 |archive-url= https://web.archive.org/web/20110726062025/http://archives.seul.org/or/dev/Sep-2002/msg00019.html}}

{{cite web |title=Tor at heart of embassy passwords leak |last=Goodin |first=Dan |website=The Register |date=10 September 2007 |access-date=20 September 2007 |url=https://www.theregister.co.uk/2007/09/10/misuse_of_tor_led_to_embassy_password_breach/ |archive-url=https://web.archive.org/web/20070925124202/http://www.theregister.co.uk/2007/09/10/misuse_of_tor_led_to_embassy_password_breach/ |archive-date=25 September 2007 |url-status=live }}

{{cite web |url=http://www.scmagazine.com.au/News/246707,egyptians-turn-to-tor-to-organise-dissent-online.aspx |title=Egyptians turn to Tor to organise dissent online |first=Nate |last=Cochrane |website=SC Magazine |date=2 February 2011 |access-date=10 December 2011 |archive-url=https://web.archive.org/web/20111213154629/http://www.scmagazine.com.au/News/246707,egyptians-turn-to-tor-to-organise-dissent-online.aspx |archive-date=13 December 2011 |url-status=live }}

{{cite web |url=https://www.torproject.org/projects/torbrowser/design/ |title=The Design and Implementation of the Tor Browser [DRAFT] |first1=Mike |last1=Perry |first2=Erinn |last2=Clark |first3=Steven |last3=Murdoch |website=Tor Project |date=15 March 2013 |access-date=28 April 2014 |url-status=live |archive-date=15 August 2014 |archive-url= https://web.archive.org/web/20140815233238/https://www.torproject.org/projects/torbrowser/design/}}

{{cite web |url=https://www.torproject.org/docs/bridges |title=Tor: Bridges |website=Tor Project |access-date=9 January 2011 |archive-date=12 May 2012 |archive-url=https://web.archive.org/web/20120512012603/https://www.torproject.org/docs/bridges |url-status=live }}

{{cite web |url=https://www.torproject.org/docs/tor-onion-service |title=Configuring Onion Services for Tor |website=Tor Project |access-date=13 December 2018 |archive-date=15 December 2018 |archive-url=https://web.archive.org/web/20181215205835/https://www.torproject.org/docs/tor-onion-service |url-status=live }}

{{cite web |url=https://www.torproject.org/about/corepeople |title=Tor Project: Core People |website=Tor Project |access-date=17 July 2008 |archive-url=https://web.archive.org/web/20110118075745/http://www.torproject.org/about/corepeople |archive-date=18 January 2011 |url-status=dead }}

{{cite web |url=https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ?action=recall&rev=554#EntryGuards |title=TheOnionRouter/TorFAQ |access-date=18 September 2007 |quote=Tor (like all current practical low-latency anonymity designs) fails when the attacker can see both ends of the communications channel |archive-date=16 September 2020 |archive-url=https://web.archive.org/web/20200916073309/https://trac.torproject.org/projects/tor/wiki/doc/TorFAQ?action=recall&rev=554#EntryGuards |url-status=live }}

{{cite web |url=https://www.torproject.org/docs/faq#WhyCalledTor |title=Tor FAQ: Why is it called Tor? |website=Tor Project |access-date=1 July 2011 |archive-date=17 January 2016 |archive-url=https://web.archive.org/web/20160117155232/https://www.torproject.org/docs/faq#WhyCalledTor |url-status=live }}

{{cite web |url=https://www.torproject.org/docs/faq-abuse.html.en#WhatAboutCriminals |title=Doesn't Tor enable criminals to do bad things? |website=Tor Project |access-date=28 August 2013 |archive-date=17 August 2013 |archive-url=https://web.archive.org/web/20130817133027/https://www.torproject.org/docs/faq-abuse.html.en#WhatAboutCriminals |url-status=live }}

{{cite web |url=https://community.torproject.org/onion-services/overview/ |title=Tor: How do Onion Services work? |website=Tor Project |access-date=26 September 2024 }}

{{cite web |url=https://blog.torproject.org/blog/tor-security-advisory-old-tor-browser-bundles-vulnerable |title=Tor security advisory: Old Tor Browser Bundles vulnerable |first=Roger |last=Dingledine |website=Tor Project |date=5 August 2013 |access-date=28 April 2014 |archive-date=26 March 2014 |archive-url=https://web.archive.org/web/20140326223617/https://blog.torproject.org/blog/tor-security-advisory-old-tor-browser-bundles-vulnerable |url-status=live }}

{{cite web |url=https://blog.torproject.org/blog/one-cell-enough |title=One cell is enough to break Tor's anonymity |first=Roger |last=Dingledine |website=Tor Project |date=18 February 2009 |access-date=9 January 2011 |archive-date=20 September 2010 |archive-url=https://web.archive.org/web/20100920113629/http://blog.torproject.org/blog/one-cell-enough |url-status=live }}

{{cite web |url=https://www.torproject.org/about/sponsors.html.en |title=Tor: Sponsors |website=Tor Project |access-date=11 December 2010 |archive-date=27 July 2011 |archive-url=https://web.archive.org/web/20110727154342/https://www.torproject.org/about/sponsors.html.en |url-status=live }}

{{cite web |url=https://metrics.torproject.org/networksize.html |title=Tor Server Status |publisher=Tor Project – Metrics |access-date=7 July 2021 |archive-date=7 June 2020 |archive-url=https://web.archive.org/web/20200607104824/https://metrics.torproject.org/networksize.html |url-status=live }}

{{cite conference |url=https://www.usenix.org/events/leet11/tech/full_papers/LeBlond.pdf |title=One Bad Apple Spoils the Bunch: Exploiting P2P Applications to Trace and Profile Tor Users |first1=Stevens |last1=Le Blond |first2=Pere |last2=Manils |first3=Abdelberi |last3=Chaabane |first4=Mohamed |last4=Ali Kaafar |first5=Claude |last5=Castelluccia |first6=Arnaud |last6=Legout |first7=Walid |last7=Dabbous |conference=4th USENIX Workshop on Large-Scale Exploits and Emergent Threats (LEET '11) |publisher=National Institute for Research in Computer Science and Control |date=March 2011 |access-date=13 April 2011 |archive-date=27 April 2011 |archive-url=https://web.archive.org/web/20110427023454/https://www.usenix.org/events/leet11/tech/full_papers/LeBlond.pdf |url-status=live }}

{{cite conference |last1=Dingledine |first1=Roger |last2=Mathewson |first2=Nick |last3=Syverson |first3=Paul |title=Tor: The Second-Generation Onion Router |book-title=Proc. 13th USENIX Security Symposium |place=San Diego, California |date=13 August 2004 |url=http://www.usenix.org/events/sec04/tech/dingledine.html |access-date=17 November 2008 |conference= |archive-date=9 August 2011 |archive-url=https://web.archive.org/web/20110809060244/http://www.usenix.org/events/sec04/tech/dingledine.html |url-status=live }}

{{cite web |url=http://wiki.vuze.com/w/Tor |title=Tor |website=Vuze |access-date=3 March 2010 |archive-date=30 April 2013 |archive-url=https://web.archive.org/web/20130430035208/http://wiki.vuze.com/w/Tor |url-status=live }}

{{cite web |url=https://www.theverge.com/2013/3/11/4091186/interview-uncut-jacob-appelbaum |title=Interview uncut: Jacob Appelbaum |author=Sirius, R. U. |website=theverge.com |date=11 March 2013 |access-date=17 September 2017 |archive-date=20 October 2014 |archive-url=https://web.archive.org/web/20141020223354/http://www.theverge.com/2013/3/11/4091186/interview-uncut-jacob-appelbaum |url-status=live }}

{{cite magazine |url=https://www.wired.com/threatlevel/2013/09/freedom-hosting-fbi/ |title=FBI Admits It Controlled Tor Servers Behind Mass Malware Attack |first=Kevin |last=Poulsen |magazine=Wired |date=13 September 2013 |access-date=22 December 2013 |archive-date=21 December 2013 |archive-url=https://web.archive.org/web/20131221024649/http://www.wired.com/threatlevel/2013/09/freedom-hosting-fbi/ |url-status=live }}

{{cite magazine |url=https://www.wired.com/2013/08/freedom-hosting/ |title=Feds Are Suspects in New Malware That Attacks Tor Anonymity |first=Kevin |last=Poulsen |magazine=Wired |date=8 May 2013 |access-date=29 April 2014 |archive-date=29 April 2014 |archive-url=https://web.archive.org/web/20140429202100/http://www.wired.com/2013/08/freedom-hosting/ |url-status=live }}

{{cite news |url=https://www.wired.com/politics/security/news/2007/09/embassy_hacks?currentPage=all |title=Rogue Nodes Turn Tor Anonymizer Into Eavesdropper's Paradise |first1=Kim |last1=Zetter |author-link=Kim Zetter |newspaper=Wired |date=10 September 2007 |access-date=16 September 2007 |archive-date=31 December 2008 |archive-url=https://web.archive.org/web/20081231175940/http://www.wired.com/politics/security/news/2007/09/embassy_hacks?currentPage=all |url-status=live }}

{{cite news |url=https://www.washingtonpost.com/blogs/the-switch/wp/2013/09/06/the-feds-pays-for-60-percent-of-tors-development-can-users-trust-it/ |title=The feds pay for 60 percent of Tor's development. Can users trust it? |first=Brian |last=Fung |work=The Switch |publisher=Washington Post |date=6 September 2013 |access-date=6 February 2014 |archive-date=9 September 2013 |archive-url=https://archive.today/20130909202619/http://www.washingtonpost.com/blogs/the-switch/wp/2013/09/06/the-feds-pays-for-60-percent-of-tors-development-can-users-trust-it/ |url-status=live }}

{{cite news |url=https://www.wsj.com/articles/SB10001424127887324677204578185382377144280 |title=Tor: an anonymous, and controversial, way to web-surf |first=Geoffrey A. |last=Fowler |work=Wall Street Journal |date=17 December 2012 |access-date=19 May 2013 |archive-date=11 March 2015 |archive-url=https://web.archive.org/web/20150311064250/http://www.wsj.com/articles/SB10001424127887324677204578185382377144280 |url-status=live }}

{{cite web |url=http://www.webupd8.org/2013/12/tor-browser-bundle-ubuntu-ppa.html |title=Tor Browser Bundle Ubuntu PPA |first=Andrei |last=Alin |website=Web Upd8 |date=2 December 2013 |access-date=28 April 2014 |archive-date=21 April 2014 |archive-url=https://web.archive.org/web/20140421220450/http://www.webupd8.org/2013/12/tor-browser-bundle-ubuntu-ppa.html |url-status=live }}

{{cite web |url=http://eng.xakep.ru/link/51074/ |title=Включаем Tor на всю катушку |trans-title=Make Tor go the whole hog |first=Антон |last=Жуков |website=Xakep |date=15 December 2009 |access-date=28 April 2014 |url-status=dead |archive-url=https://web.archive.org/web/20130901035137/http://eng.xakep.ru/link/51074/ |archive-date=1 September 2013 }}

{{Cite news |url=https://www.bbc.co.uk/news/technology-29987373 |title=Dark net experts trade theories on 'de-cloaking' after raids |date=7 November 2014 |access-date=12 November 2014 |newspaper=BBC News |last1=Lee |first1=Dave |archive-date=12 November 2014 |archive-url=https://web.archive.org/web/20141112165655/http://www.bbc.co.uk/news/technology-29987373 |url-status=live }}

{{cite web |url=https://gitlab.torproject.org/tpo/core/tor/-/graphs/main/charts |title=Repository Analytics |website=Tor Project GitLab |access-date=24 August 2022 |url-status=live |archive-date=24 June 2022 |archive-url=https://web.archive.org/web/20220624025354/https://gitlab.torproject.org/tpo/core/tor/-/graphs/main/charts }}

}}

{{Refbegin}}

• {{Cite book |title=Tor: From the Dark Web to the Future of Privacy |first=Ben |last=Collier |isbn=9780262378925 |publisher=MIT Press |url=https://direct.mit.edu/books/oa-monograph/5761/TorFrom-the-Dark-Web-to-the-Future-of-Privacy |date=2024}}
• {{cite journal |last1=Lund |first1=Brady |first2=Matt |last2=Beckstrom |date=2021 |title=The Integration of Tor into Library Services: An Appeal to the Core Mission and Values of Libraries |journal=Public Library Quarterly |volume=40 |issue=1 |pages=60–76 |doi=10.1080/01616846.2019.1696078 |s2cid=214213117 }}
• {{Cite book |title=Understanding the Usage of Anonymous Onion Services: Empirical Experiments to Study Criminal Activities in the Tor Network |first=Juha |last=Nurmi |isbn=978-952-03-1091-2 |date=24 May 2019 }}
• {{Cite book |title=Applied Cryptography |first=Bruce |last=Schneier |author-link=Bruce Schneier |isbn=978-0-471-11709-4|date=1 November 1995 |publisher=Wiley }}
• {{Cite book |title=Email Security |first=Bruce |last=Schneier |author-link=Bruce Schneier |isbn=978-0-471-05318-7 |date=25 January 1995 |publisher=Wiley |url-access=registration |url=https://archive.org/details/emailsecurityhow0000schn }}

{{Refend}}

{{Commons category|Tor project}}

• {{Official website}}
• [https://freehaven.net/anonbib/ Anonymity Bibliography]
• [https://2019.www.torproject.org Old website]
• [https://web.archive.org/web/20171220172642/https://www.torproject.org/getinvolved/mirrors.html.en Archived: Official List of mirror websites]
• [https://www.youtube.com/watch?v=JWII85UlzKw&t=0 "How Tor Browser Protects Your Privacy and Identity Online"]—Animated introduction on YouTube
• [https://media.ccc.de/v/31c3_-_6112_-_en_-_saal_2_-_201412301715_-_tor_hidden_services_and_deanonymisation_-_dr_gareth_owen Tor: Hidden Services and Deanonymisation]—Presentation at the 31st Chaos Computer Conference
• [https://torflow.uncharted.software/ TorFlow], a dynamic visualization of data flowing over the Tor network
• [https://media.ccc.de/v/32c3-7322-tor_onion_services_more_useful_than_you_think Tor onion services: more useful than you think] in a 2016 presentation at the 32nd Annual Chaos Communication Congress
• [https://www.youtube.com/watch?v=xGIE7KTJiBY&t=0 A core Tor developer lectures] at the Radboud University Nijmegen in The Netherlands on anonymity systems in 2016
• [https://web.archive.org/web/20161019151220/https://people.torproject.org/~isis/slides/2016-10-13-waterloo-handout.pdf A technical presentation] given at the University of Waterloo in Canada: Tor's Circuit-Layer Cryptography: Attacks, Hacks, and Improvements
• [https://www.youtube.com/watch?v=ShrZ4B9R3NQ&t=0 A Presentation at the March 2017 BSides Vancouver Conference on security practices on Tor's hidden services] given by Sarah Jamie Lewis

{{Tor project}}

{{Tor hidden services}}

{{Internet censorship circumvention technologies}}

{{Navboxes|list=

{{Cryptographic software}}

{{Privacy}}

{{Routing software}}

{{Web browsers|desktop}}

}}

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