AARD code

This XOR-encrypted, self-modifying, and deliberately obfuscated x86 assembly code used a variety of undocumented MS-DOS structures and functions to detect if a machine was running DR DOS. The code was present in the installer, in the WIN.COM file used to load Windows, and in several other EXE and COM files within Windows 3.1.

The AARD code was discovered by Geoff Chappell on 17 April 1992 and further analyzed and documented in a joint research effort with Andrew Schulman. The name "AARD code" came from the letters "AARD" that were found in a hex dump of the Windows 3.1 installer; this turned out to be the signature of Microsoft programmer Aaron R. Reynolds (1955–2008).

Microsoft disabled the AARD code for the final release of Windows 3.1, but did not remove it so it could be later reactivated by the change of a single byte.

DR DOS publisher Digital Research released a patch named "business update" in 1992 to bypass the AARD code.

The rationale for the AARD code came to light when internal memos were released during the United States v. Microsoft Corp. antitrust case in 1999. Internal memos released by Microsoft revealed that the specific focus of these tests was DR DOS. At one point, Microsoft CEO Bill Gates sent a memo to a number of employees that said, "You never sent me a response on the question of what things an app would do that would make it run with MSDOS and not run with DR-DOS. Is there{{sic}} feature they have that might get in our way?" Microsoft Senior Vice President Brad Silverberg later sent another memo, saying, "What the [user] is supposed to do is feel uncomfortable, and when he has bugs, suspect that the problem is dr-dos and then go out to buy ms-dos."

After Novell bought DR DOS and renamed it "Novell DOS", Microsoft Co-President Jim Allchin wrote in a memo, "If you're going to kill someone there isn't much reason to get all worked up about it and angry. Any discussions beforehand are a waste of time. We need to smile at Novell while we pull the trigger."

Novell DOS changed hands again. The new owner, Caldera, Inc., began a lawsuit against Microsoft over the AARD code, Caldera v. Microsoft, which was later settled. It was originally believed that the settlement was around $150 million,{{efn|approximately ${{formatprice|{{inflation|US|150000000|2000}}}} in {{inflation/year|US}}}} but in November 2009, the settlement agreement was released, and the total was revealed to be $280 million.{{efn|approximately ${{formatprice|{{inflation|US|280000000|2000}}}} in {{inflation/year|US}}}}

• Bug compatibility
• Fear, uncertainty, and doubt (FUD)
• Halloween documents

{{notelist}}

{{reflist|refs=

{{cite web |author-first=Geoff |author-last=Chappell |title=Record of AARD Research |date=2011-11-24 |orig-year=1999-09-03, 1992-04-17 |url=http://www.geoffchappell.com/notes/windows/archive/aard/research.htm |access-date=2016-11-25 |url-status=live |archive-url=https://web.archive.org/web/20161125114745/http://www.geoffchappell.com/notes/windows/archive/aard/research.htm |archive-date=2016-11-25}} (Web article published by Geoff Chappell on 3 September 1999 about an e-mail sent to Andrew Schulman on 17 April 1992.)

{{cite web |author-first=Geoff |author-last=Chappell |title=First Public AARD Details |date=2011-11-24 |orig-year=1999-05-08 |url=http://www.geoffchappell.com/notes/windows/archive/aard/firstpublic.htm |url-status=dead |archive-url=https://web.archive.org/web/20130402004936/http://www.geoffchappell.com/notes/windows/archive/aard/firstpublic.htm |archive-date=2013-04-02}}

{{cite journal |title=Examining the Windows AARD Detection Code - A serious message--and the code that produced it |author-first=Andrew |author-last=Schulman |date=September 1993 |journal=Dr. Dobb's Journal |volume=18 |issue=9 |id=#204 |publisher=Miller Freeman, Inc. |pages=42, 44–48, 89 |url=http://www.ddj.com/documents/s=1030/ddj9309d/9309d.htm |access-date=2013-10-05 |url-status=dead |archive-url=https://web.archive.org/web/20051210072152/http://www.ddj.com/documents/s%3D1030/ddj9309d/9309d.htm |archive-date=2005-12-10}}

{{cite book |author-first1=Andrew |author-last1=Schulman |author-first2=Ralf D. |author-last2=Brown |author-link2=Ralf D. Brown |author-first3=David |author-last3=Maxey |author-first4=Raymond J. |author-last4=Michels |author-first5=Jim |author-last5=Kyle |title=Undocumented DOS: A programmer's guide to reserved MS-DOS functions and data structures - expanded to include MS-DOS 6, Novell DOS and Windows 3.1 |publisher=Addison Wesley |edition=2 |date=1994 |orig-year=November 1993 |isbn=0-201-63287-X |url-access=registration |url=https://archive.org/details/undocumenteddosp00andr_0}} (xviii+856+vi pages, 3.5-inch floppy) Errata: [https://web.archive.org/web/20190417215556/http://www.cs.cmu.edu/afs/cs/user/ralf/pub/books/UndocumentedDOS/errata.ud2][https://web.archive.org/web/20190417212906/https://www.pcjs.org/pubs/pc/programming/Undocumented_DOS/#errata-2nd-edition]

{{cite web |url=http://www.legacy.com/obituaries/seattletimes/obituary.aspx?pid=114850359 |title=Aaron R. Reynolds |work=Seattle Times |series=Obituary |via=Legacy |date=2008-08-04 |url-status=live |archive-date=2016-03-04 |archive-url=https://web.archive.org/web/20160304073802/http://www.legacy.com/obituaries/seattletimes/obituary.aspx?pid=114850359}}

{{cite journal |author-last=Dellert |author-first=Brian |date=1998-10-21 |title=Microsoft Plays Hardball |journal=Eat the State! |volume=3 |issue=7 |url=http://eatthestate.org/03-07/MicrosoftPlaysHardball.htm |access-date=2008-08-21 |url-status=dead |archive-url=https://web.archive.org/web/20080420194217/http://eatthestate.org/03-07/MicrosoftPlaysHardball.htm |archive-date=2008-04-20}}

{{cite web |url=http://jerrypournelle.com/debates/Microsoft1.html |title=The Microsoft Monopoly Debates |access-date=2008-08-21 |author-last=Pournelle |author-first=Jerry |author-link=Jerry Pournelle |date=2000-04-01 |archive-url=https://web.archive.org/web/20080829102926/http://www.jerrypournelle.com/debates/Microsoft1.html |archive-date=2008-08-29 |url-status=dead}}

{{cite web |title=25 years of DR DOS history - Digital Research DOS history |author-first=Matthias R. |author-last=Paul |date=2000-09-18 |publisher=FreeDOS.org |url=http://www.freedos.org/freedos/news/press/2000-drdos-hist.txt |access-date=2013-10-05 |url-status=dead |archive-url=https://web.archive.org/web/20161125115620/http://www.freedos.org/technotes/press/2000-drdos-hist.txt |archive-date=2016-11-25 |quote=See footnote #19 (BDOS 1067h "DR DOS 6.0 Windows 3.1 update, April 1992"; 1992-03, 1992-04-07: "This public DR DOS 6.0 update only includes patches addressing full Windows 3.1 compatibility. There should have been a full "business update" for registered users, shipping a little bit later."), #27 (BDOS 1072h "Novell DOS 7 Panther/Smirnoff BETA 3", 1993-09: "This issue does not have workarounds for Windows 3.1 AARD code."), #29 (BDOS 1072h "Novell DOS 7 German release"; 1994-02-22: "This issue is known to have workarounds for Windows 3.1 AARD code. This should also apply to the earlier English issue.")}}

{{cite web |title=How MS played the incompatibility card against DR-DOS - Real bear-traps, and spurious errors |author-first=Graham |author-last=Lea |author-link=Graham Lea (journalist) |date=1999-11-05 |work=The Register |url=https://www.theregister.co.uk/1999/11/05/how_ms_played_the_incompatibility/ |access-date=2013-09-26 |url-status=live |archive-url=https://web.archive.org/web/20161125041121/https://www.theregister.co.uk/1999/11/05/how_ms_played_the_incompatibility/ |archive-date=2016-11-25}}

{{cite news |title=Windows Warning Resurfaces in Suit |author-first=Ted |author-last=Bridis |work=Associated Press |date=1998-08-28 |url=https://apnews.com/f98bb622c4df848fee85f8ede1f32f72 |access-date=2016-11-25 |url-status=live |archive-url=https://web.archive.org/web/20161125043840/http://www.apnewsarchive.com/1998/Windows-Warning-Resurfaces-in-Suit/id-f98bb622c4df848fee85f8ede1f32f72 |archive-date=2016-11-25}}

{{cite web |title=In the United States District Court - District of Utah, Central Division - Caldera, Inc. vs. Microsoft Corporation - Consolidated statement of facts in support of its responses to motions for summary judgement by Microsoft Corporation - Case No. 2:96CV 0645B |author-first1=Stephen Daily |author-last1=Susman |author-link1=Stephen Daily Susman |author-first2=Charles R. |author-last2=Eskridge III |author-link2=Charles R. Eskridge III |author-first3=James T. |author-last3=Southwick |author-first4=Harry P. |author-last4=Susman |author-first5=Parker C. |author-last5=Folse III |author-first6=Ralph H. |author-last6=Palumbo |author-first7=Matthew R. |author-last7=Harris |author-first8=Philip S. |author-last8=McCune |author-first9=Lynn M. |author-last9=Engel |author-first10=Stephen J. |author-last10=Hill |author-first11=Ryan E. |author-last11=Tibbitts |date=April 1999 |type=Court document |publisher=Caldera, Inc. |url=http://www.maxframe.com/DR/Info/fullstory/factstat.html |access-date=2018-08-05 |url-status=dead |archive-url=https://web.archive.org/web/20180805184350/http://www.maxframe.com/DR/Info/fullstory/factstat.html |archive-date=2018-08-05}}

{{cite web |title=In the United States District Court - District of Utah, Central Division - Caldera, Inc. vs. Microsoft Corporation - Case No. 2:96CV 0645B - Caldera, Inc.'s Memorandum in opposition to defendant's motion for partial Summary Judgment on plaintiff's "Technological Tying" claim |author-first1=Stephen Daily |author-last1=Susman |author-link1=Stephen Daily Susman |author-first2=Charles R. |author-last2=Eskridge III |author-link2=Charles R. Eskridge III |author-first3=Harry P. |author-last3=Susman |author-first4=James T. |author-last4=Southwick |author-first5=Parker C. |author-last5=Folse III |author-first6=Timothy K. |author-last6=Borchers |author-first7=Ralph H. |author-last7=Palumbo |author-first8=Matthew R. |author-last8=Harris |author-first9=Lynn M. |author-last9=Engel |author-first10=Philip S. |author-last10=McCune |author-first11=Lawrence C. |author-last11=Locker |author-first12=Max D. |author-last12=Wheeler |author-first13=Stephen J. |author-last13=Hill |author-first14=Ryan E. |author-last14=Tibbitts |date=May 1999 |type=Court document |publisher=Caldera, Inc. |url=http://www.maxframe.com/DR/Info/fullstory/tech.html |access-date=2018-08-05 |url-status=dead |archive-url=https://web.archive.org/web/20180805142843/http://www.maxframe.com/DR/Info/fullstory/tech.html |archive-date=2018-08-05}}

{{cite web |title=Caldera submits evidence to counter Microsoft's motions for partial summary judgment |author-first=Lyle |author-last=Ball |author-link=Lyle Ball (Caldera) |publisher=Caldera, Inc. |date=1999-04-28 |type=Press release |url=http://www.maxframe.com/DR/Info/fullstory/factrel.html |access-date=2018-08-05 |url-status=live |archive-url=https://web.archive.org/web/20180805143119/http://www.maxframe.com/DR/Info/fullstory/factrel.html |archive-date=2018-08-05}}

{{cite journal |title=In the United States District Court - District of Utah, Central Division - Caldera, Inc. vs. Microsoft Corporation - Case No. 2:96CV 0645B - First amended complaint and jury demand |type=Court document |author-first1=Max D. |author-last1=Wheeler |author-first2=Stephen J. |author-last2=Hill |author-first3=Ryan E. |author-last3=Tibbitts |author-first4=Stephen Daily |author-last4=Susman |author-link4=Stephen Daily Susman |author-first5=Charles R. |author-last5=Eskridge III |author-link5=Charles R. Eskridge III |author-first6=Thomas W. |author-last6=Paterson |author-first7=Stuart J. |author-last7=Dow |author-first8=Ralph H. |author-last8=Palumbo |author-first9=Parker C. |author-last9=Folse III |author-first10=Timothy K. |author-last10=Borchers |journal=Tech Law Journal |url=http://www.techlawjournal.com/courts/caldera/Default.htm |url-status=live |archive-url=https://web.archive.org/web/20161125044920/http://www.techlawjournal.com/courts/caldera/Default.htm |archive-date=2016-11-25}}

{{cite news |author-first=Dan |author-last=Goodin |title=Microsoft emails focus on DR-DOS threat |url=http://news.cnet.com/2100-1001-225129.html |work=CNET News |date=1999-04-28 |access-date=2008-08-21 |url-status=live |archive-url=https://web.archive.org/web/20160310065721/https://www.cnet.com/news/microsoft-emails-focus-on-dr-dos-threat/ |archive-date=2016-03-10}}

{{cite news |author-first=Graham |author-last=Lea |author-link=Graham Lea (journalist) |title=Caldera vs Microsoft - the settlement |url=http://news.bbc.co.uk/2/hi/business/600488.stm |work=BBC News |date=2000-01-13 |access-date=2008-08-21 |archive-url=https://web.archive.org/web/20081005102243/http://news.bbc.co.uk/2/hi/business/600488.stm |archive-date=2008-10-05 |url-status=live}}

{{cite news |author-first=Joe |author-last=Wilcox |title=Caldera settlement shows a new side of Microsoft |url=http://news.cnet.com/2100-1001-235465.html |publisher=cnet |date=2000-01-11 |access-date=2009-01-19 |url-status=live |archive-url=https://web.archive.org/web/20161125113400/https://www.cnet.com/news/caldera-settlement-shows-a-new-side-of-microsoft/ |archive-date=2016-11-25}}

{{cite web |author-first=Pamela |author-last=Jones |author-link=Pamela Jones |title=Exhibits to Microsoft's Cross Motion for Summary Judgment in Novell WordPerfect Case |url=http://www.groklaw.net/article.php?story=20091120165256836 |work=Groklaw |date=2009-11-23 |access-date=2011-10-22 |url-status=live |archive-url=https://archive.today/20130821080038/http://www.groklaw.net/article.php?story=20091120165256836 |archive-date=2013-08-21 |quote=[…] exhibits attached to Microsoft's Memorandum of Law in support of Microsoft's cross motion for summary judgment in the Novell v. Microsoft antitrust litigation. We finally find out what Microsoft paid Caldera to settle the DrDOS litigation back in 2000: $280 million. We even get to read the settlement agreement. It's attached as an exhibit. […] The settlement terms were sealed for all these years, but […] now that mystery is solved. […] We also find out what Caldera/Canopy then paid Novell from that $280 million: $35.5 million at first, and then after Novell successfully sued Canopy in 2004, Caldera's successor-in-interest on this matter, an additional $17.7 million, according to page 16 of the Memorandum. Microsoft claims that Novell is not the real party in interest in this antitrust case, and so it can't sue Microsoft for the claims it has lodged against it, because, Microsoft says, Novell sold its antitrust claims to Caldera when it sold it DrDOS. So the exhibits are trying to demonstrate that Novell got paid in full, so to speak, via that earlier litigation. As a result, we get to read a number of documents from the Novell v. Canopy litigation. Novell responds it retained its antitrust claims in the applications market. […]}}

{{cite journal |title=Microsoft: Vorgetäuschter Bug legte DR-DOS lahm |language=de |author-first=Egbert |author-last=Meyer |date=1998-08-27 |journal=Heise Online |publisher=Verlag Heinz Heise |url=https://www.heise.de/newsticker/meldung/Microsoft-Vorgetaeuschter-Bug-legte-DR-DOS-lahm-14173.html |access-date=2018-07-14 |url-status=live |archive-url=https://web.archive.org/web/20180714175147/https://www.heise.de/newsticker/meldung/Microsoft-Vorgetaeuschter-Bug-legte-DR-DOS-lahm-14173.html |archive-date=2018-07-14}} [https://heise.de/-14173]

{{cite web |title=Microsoft's memorandum in opposition to Novell's renewed motion for summary judgement on Microsoft's affirmative defenses and in support of Microsoft's cross-motion for summary judgement |author-first1=Richard J. |author-last1=Wallis |author-first2=Steven J. |author-last2=Aeschbacher |author-first3=Mark M. |author-last3=Bettilyon |author-first4=G. Stewar |author-last4=Webb, Jr. |author-first5=David B. |author-last5=Tulchin |author-first6=Steven L. |author-last6=Holley |date=2009-11-13 |location=United States District Court, District of Maryland |type=Court document |id=Novell, Inc. v. Microsoft Corporation, Civil Action No. JFM-05-1087 |page=16 |url=http://www.groklaw.net/pdf2/NovvMS-104-2.pdf |access-date=2018-08-03 |url-status=live |archive-url=https://web.archive.org/web/20190524154518/http://www.groklaw.net/pdf2/NovvMS-104-2.pdf |archive-date=2019-05-24 |quote=[…] Microsoft paid $280 million to Caldera to settle the case, and $35.5 million of the settlement proceeds were provided by Caldera to Novell as a so-called "royalty." […] Dissatisfied with that amount, Novell filed suit in June 2000 against Caldera (succeeded by The Canopy Group), alleging that Novell was entitled to even more. […] Novell ultimately prevailed, adding $17.7 million to its share of the monies paid by Microsoft to Caldera, for a total of more than $53 million […]}}

{{cite web |title=Settlement agreement - Microsoft Corporation and Caldera, Inc. reach agreement to settle antitrust lawsuit |author-first1=Thomas W. |author-last1=Burt |author-first2=Bryan Wayne |author-last2=Sparks |author-link2=Bryan Wayne Sparks |date=2000-01-07 |id=Case 1:05-cv-01087-JFM, Document 104-8, Filed 2009-11-13; NOV00107061-NOV00107071; LT2288-LT2298; Lan12S311263739.1; Exhibit A |type=Faxed court document |url=http://www.groklaw.net/pdf2/NovvMS-104-8.pdf |access-date=2018-08-03 |url-status=live |archive-url=https://web.archive.org/web/20170704220659/http://groklaw.net/pdf2/NovvMS-104-8.pdf |archive-date=2017-07-04 |quote=[…] Microsoft will pay to Caldera, by wire transfer in accordance with written instructions provided by Caldera, the amount of two hundred eighty million dollars ($280,000,000), as full settlement of all claims or potential claims covered by this agreement […]}} (NB. This document of the Caldera v. Microsoft case was an exhibit in the Novell v. Microsoft and Comes v. Microsoft cases.)

{{cite news |title=Microsoft Will Pay $275 Million To Settle Lawsuit From Caldera |author-first=Lee |author-last=Gomes |date=2000-01-11 |newspaper=The Wall Street Journal |url=https://www.wsj.com/articles/SB947543007415899052 |access-date=2019-11-24 |url-status=live |archive-url=https://web.archive.org/web/20161231130504/http://www.wsj.com/articles/SB947543007415899052 |archive-date=2016-12-31 |quote=Microsoft Corp. agreed to pay an estimated $275 million to settle an antitrust lawsuit by Caldera Inc., heading off a trial that was likely to air nasty allegations from a decade ago. […] Microsoft and Caldera, a small Salt Lake City software company that brought the suit in 1996, didn't disclose terms of the settlement. Microsoft, though, said it would take a charge of three cents a share for the agreement in the fiscal third quarter ending March 31 […] the company has roughly 5.5 billion shares outstanding […]}}

{{cite web |title=msdos detection - hot job for you |date=1993-02-24 |orig-year=1991-12-06 |author-first=Aaron R. |author-last=Reynolds |type=Court document |id=MS-PCA 1164868-1164869; X0532177-X0532178; Comes v. Microsoft Exhibit 1133; Gates Deposition Exhibit 85 |url=http://antitrust.slated.org/www.iowaconsumercase.org/011607/1000/PX01133.pdf |access-date=2018-08-04 |url-status=live |archive-url=https://web.archive.org/web/20180803194008/http://antitrust.slated.org/www.iowaconsumercase.org/011607/1000/PX01133.pdf |archive-date=2018-08-03}} (NB. This court document is a copy of a mail by Aaron Reynolds written in 1991 and forwarded by one of its recipients, Phil Barrett, in 1993.)

{{cite web |title=Customers and Novell |date=1993-09-18 |author-first=James Edward |author-last=Allchin |author-link=James Edward Allchin |type=Court document |id=MS 0186262-0186263; Comes v. Microsoft Exhibit 1793; Allchin Deposition Exhibit 14 |pages=72–73 |url=http://antitrust.slated.org/www.iowaconsumercase.org/assets/attachments/PLEX01793.pdf |access-date=2018-08-04 |url-status=live |archive-url=https://web.archive.org/web/20180803203234/http://antitrust.slated.org/www.iowaconsumercase.org/assets/attachments/PLEX01793.pdf |archive-date=2018-08-03}}

{{cite magazine |title=DR DOS 6.0 does Windows 3.1 |date=1992-04-20 |magazine=Computerworld |series=News Shorts |page=6 |url=https://books.google.com/books?id=w1yCn870hscC&pg=PA6 |access-date=2019-07-22 |url-status=live |archive-url=https://archive.today/20190722175928/https://books.google.nl/books?id=w1yCn870hscC&pg=PA6&lpg=PA6&redir_esc=y%23v=onepage&q&f=false |archive-date=2019-07-22}}

}}

• {{cite web |author-first=Larry |author-last=Osterman |title=AARDvarks in your code |date=2004-08-12 |url=http://blogs.msdn.com/larryosterman/archive/2004/08/12/213681.aspx |access-date=2016-11-25 |url-status=live |archive-url=https://web.archive.org/web/20161125120335/https://blogs.msdn.microsoft.com/larryosterman/2004/08/12/aardvarks-in-your-code/ |archive-date=2016-11-25}}
• {{cite web |author-first=Larry |author-last=Osterman |title=So why didn't the Windows guys just remove the AARD code from the system? |url=http://blogs.msdn.com/larryosterman/archive/2004/08/13/214338.aspx |access-date=2016-11-25 |date=2004-08-13 |url-status=live |archive-url=https://web.archive.org/web/20161125120727/https://blogs.msdn.microsoft.com/larryosterman/2004/08/13/so-why-didnt-the-windows-guys-just-remove-the-aard-code-from-the-system/ |archive-date=2016-11-25}}
• {{cite web |author-first=Geoff |author-last=Chappell |title=The AARD Code |date=1999-05-08 |url=http://members.ozemail.com.au/~geoffch@ozemail.com.au/editorial/aard/ |url-status=dead |archive-url=https://web.archive.org/web/20100113064451/http://members.ozemail.com.au/~geoffch%40ozemail.com.au/editorial/aard/ |archive-date=2010-01-13}} (Details and initial discovery)
• {{cite journal |title=Old e-mail dogs Microsoft in fighting antitrust suits |author-first=John R. |author-last=Wilke |date=1998 |journal=The Wall Street Journal |publisher=Dow Jones & Company, Inc. |url=http://alumni.media.mit.edu/~cwren/windoze95/190860.html |access-date=2016-11-25 |url-status=live |archive-url=https://web.archive.org/web/20161125121459/http://alumni.media.mit.edu/~cwren/windoze95/190860.html |archive-date=2016-11-25}} (Caldera v. Microsoft details)
• {{cite web |title=Survey Says: "MS OK", but Dr. John is not convinced |author=Dr John |date=1999 |work=KickAss Gear |url=http://kickassgear.com/Articles/Microsoft.htm |access-date=2016-11-25 |url-status=live |archive-url=https://web.archive.org/web/20161125122036/http://kickassgear.com/Articles/Microsoft.htm |archive-date=2016-11-25}} (Site with email excerpts from Microsoft and an example of tripping the AARD code (XMS error))

{{DEFAULTSORT:Aard Code}}

Category:Windows components

Category:Microsoft criticisms and controversies