Netcat

{{Redirect|Ncat||NCAT (disambiguation){{!}}NCAT}}

{{Infobox software

| name = netcat

| logo =

| screenshot = frameless

| caption = The {{code|netcat}} command

| author = *Hobbit*

| developer = Avian Research

| released = {{Start date and age|1995|10|28}}{{cite web

| url=https://seclists.org/bugtraq/1995/Oct/28

| title=New tool available: Netcat

| author=Hobbit

| date=1995-10-28

| work=Bugtraq mailing list

| access-date=2019-06-05}}

| latest_release_version = 1.10

| latest_release_date = {{Start date and age|1996|03||df=yes}}

| operating_system = Unix and Unix-like, DOS, Microsoft Windows, Windows CE

| genre = Network utility

| license = Original version: custom, permissive license
GNU version: GPL
OpenBSD version: BSD

| website = {{URL|nc110.sourceforge.io}}

| discontinued = yes

}}

netcat (often abbreviated to nc) is a computer networking utility for reading from and writing to network connections using TCP or UDP. The command is designed to be a dependable back-end that can be used directly or easily driven by other programs and scripts. At the same time, it is a feature-rich network debugging and investigation tool, since it can produce almost any kind of connection its user could need and has a number of built-in capabilities.

It is able to perform port scanning, file transferring and port listening.

Features

The original netcat's features include:{{Cite book |last=Vacca |first=John R. |title=Guide to Wireless Network Security |publisher=Springer Publishing |year=2006 |isbn=978-0387954257 |pages=266 |language=en}}

Outbound or inbound connections, TCP or UDP, to or from any ports
Full DNS forward/reverse checking, with appropriate warnings
Ability to use any local source port
Ability to use any locally configured network source address
Built-in port-scanning capabilities, with randomization
Built-in loose source-routing capability
Can read command line arguments from standard input
Slow-send mode, one line every N seconds
Hex dump of transmitted and received data
Optional ability to let another program service establish connections
Optional telnet-options responder

Rewrites like GNU's and OpenBSD's support additional features. For example, OpenBSD's nc supports TLS, and GNU netcat natively supports a tunneling mode supporting UDP and TCP (optionally allowing one to be tunneled over the other) in a single command,{{cite web

| url = http://netcat.sourceforge.net/

| title = The GNU Netcat project

| author = Giovanni Giacobbi

| date = 2006-11-01

| access-date = 2020-03-22}} where other versions may require piping data from one netcat instance to another.

Ports and reimplementations

The original version of netcat was a Unix program. The last version (1.10) was released in March 1996.{{cite web |date=2008-02-14 |title=Netcat 1.10 |url=http://nc110.sourceforge.net/ |access-date=2019-06-05 |website=nc110.sourceforge.net}}

There are several implementations on POSIX systems, including rewrites from scratch like GNU netcat{{cite web

| url = http://netcat.sourceforge.net/

| title = The GNU Netcat project

| author = Giovanni Giacobbi

| date = 2006-11-01

| access-date = 2019-06-05}} or OpenBSD netcat,{{cite web

| url = https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/nc/

| title = OpenBSD CVSWeb: /src/usr.bin/nc/

| publisher = OpenBSD

| access-date = 2019-06-05}}

the latter of which supports IPv6 and TLS. The OpenBSD version has been ported to the FreeBSD base,{{cite web

| url = https://svnweb.freebsd.org/base/release/5.4.0/usr.bin/nc/Makefile?revision=141394&view=markup

| title = Contents of /release/5.4.0/usr.bin/nc/Makefile

| author = delphij

| date = 2005-02-06

| publisher=FreeBSD

| access-date = 2019-06-05}}

Windows/Cygwin,{{cite web

| url = https://www.daemon.de/Netcat

| title = Netcat OpenBSD Cygwin Port 1.10.2.3

| author = Thomas Linden

| website = Daemon.de

| date = 2011-03-02

| access-date = 2019-06-05}}

and Linux.[https://tracker.debian.org/pkg/netcat-openbsd Debian netcat-openbsd]

Mac OS X comes with netcat installed as of OSX 10.13 or users can use MacPorts to install a variant.{{cite web

| url = https://www.macports.org/ports.php?by=name&substr=netcat

| title = MacPorts Portfiles: netcat

| publisher = MacPorts

| access-date = 2019-06-05}}

A DOS version of netcat called NTOOL is included in the FreeDOS Package group Networking.{{cite web

| url=https://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/distributions/1.2/repos/pkg-html/group-net.html

| title=ibiblio.org FreeDOS Group -- Networking

| date=2019-03-03

| publisher=ibiblio

| access-date=2019-06-05}} It is based on the WatTCP stack and licensed under the European Union Public Licence Version 1.1.{{cite web

| url=https://www.bttr-software.de/products/jhoffmann/

| title=various tools

| author=Jürgen Hoffmann

| date=2018-11-03

| access-date=2019-06-05}}

Known ports for embedded systems includes versions for Windows CE (named "Netcat 4 wince"{{cite web

| url = https://www.dr-bischoff.de/wince/Andreas_WINCE_stuff.html#netcat

| title = Netcat 4 wince

| author = Andreas Bischoff

| date = 2010-06-07

| access-date = 2019-06-05}}) or for the iPhone.{{cite web

| url = http://svn.telesphoreo.org/trunk/data/netcat/

| title = Revision 835: /trunk/data/netcat

| date = 2008-08-18

| access-date = 2019-06-05}}

BusyBox includes by default a lightweight version of netcat named mini-netcat.{{Cite web|url=https://git.busybox.net/busybox/tree/networking/nc.c?h=1_37_0|title=nc: mini-netcat - built from the ground up for LRP|website=git.busybox.net}} Another version with more features, named bloaty nc, is also available.{{Cite web|url=https://git.busybox.net/busybox/tree/networking/nc_bloaty.c?h=1_37_0|title=busybox - bloaty nc|website=git.busybox.net}}

Solaris 11 includes netcat implementation based on OpenBSD netcat.{{Cite web|url=https://docs.oracle.com/cd/E36784_01/html/E37476/gnqeb.html|title= Oracle Solaris 11.2 Information Library - Performing TCP and UDP Administration With the netcat Utility|website=docs.oracle.com}}

Socat{{cite web

| url = http://www.dest-unreach.org/socat/

| title = socat - Multipurpose relay

| date = 2019-04-06

| access-date = 2019-06-05}} is a more complex variant of netcat. It is larger and more flexible and has more options that must be configured for a given task. On February 1, 2016, Santiago Zanella-Beguelin and Microsoft Vulnerability Research issued a security advisory regarding a composite Diffie-Hellman parameter which had been hard-coded into the OpenSSL implementation of socat.{{cite web

| url=http://www.dest-unreach.org/socat/contrib/socat-secadv7.html

| title=Socat security advisory 7

| date=2016-02-01

| access-date=2019-06-05}} The implausibility that a composite might have been unintentionally introduced where a prime number is required has led to the suspicion of sabotage to introduce a backdoor software vulnerability.{{cite web

| url=https://www.theregister.co.uk/2016/02/03/socat_backdoor_fix/

| title=Socat slams backdoor, sparks thrilling whodunit

| first=Richard

| last=Chirgwin

| date=2016-02-03

| publisher=The Register

| access-date=2019-06-05}} This socat bug affected version 1.7.3.0 and 2.0.0-b8 it was corrected in following releases from 1.7.3.1 and 2.0.0-b9.

Cryptcat{{cite web

| url = http://cryptcat.sourceforge.net/

| title = CryptCat Project

| date = 2005-10-18

| access-date = 2019-06-05}} is a version of netcat with integrated transport encryption capabilities.

In the middle of 2005, Nmap announced another netcat incarnation called Ncat.{{cite web

| url = https://nmap.org/ncat/

| title = Ncat - Netcat for the 21st Century

| publisher = Nmap

| date = 2009-07-08

| access-date = 2019-06-05}} It features new possibilities such as "Connection Brokering", TCP/UDP Redirection, SOCKS4 client and server support, ability to "Chain" Ncat processes, HTTP CONNECT proxying (and proxy chaining), SSL connect/listen support and IP address/connection filtering. Like Nmap, Ncat is cross-platform.

On some systems, modified versions or similar netcat utilities go by the command name(s) nc, ncat, pnetcat, socat, sock, socket, sbd.

=ncat=

Ncat is a similar tool to netcat provided by Nmap suite. "While Ncat isn't built on any code from the “traditional” Netcat (or any other implementation), Ncat is most definitely based on Netcat in spirit and functionality."{{Cite web

| url=https://manpages.debian.org/stretch/nmap/ncat.1.en.html

| title=ncat(1) - Ncat Reference Guide

| date=2016-12-18

| website=manpages.debian.org

| access-date=2019-06-05}}

Ncat features includes: ability to chain Ncats together, redirect both TCP and UDP ports to other sites, SSL support, and proxy connections via SOCKS4 or HTTP (CONNECT method) proxies (with optional proxy authentication as well).{{Cite web|url=https://nmap.org/ncat/|title = Ncat - Netcat for the 21st Century}}