* The Creeper virus was an experimental self-replicating program written by Bob Thomas at BBN in 1971. Creeper infected DEC PDP-10 computers running the TENEX operating system. Creeper gained access via the ARPANET and copied itself to the remote system where the message, "I'm the creeper, catch me if you can!" was displayed. The Reaper program was created to delete Creeper.
* The Wabbit virus was not really a virus but more of a fork bomb, a program that multiplies copies of itself on a single computer, named for the speed at which it clogged the system with copies of itself, reducing system performance, before reaching a threshold and crashing.
* ANIMAL was a popular game written for the UNIVAC 1108 which asked a number of questions to the user in an attempt to guess the type of animal that the user was thinking of. When run, the related program PERVADE would also create a copy of itself and ANIMAL in every directory to which the current user had access. It spread across the multi-user UNIVACs when users with overlapping permissions discovered the game, and to other computers when tapes were shared. The program was carefully written to avoid damage to existing file or directory structure, and to not copy itself if permissions did not exist or if damage could result. Its spread was therefore halted by an OS upgrade which changed the format of the file status tables that PERVADE used for safe copying. Though non-malicious, "Pervading Animal" represents the first Trojan "in the wild".
* Jürgen Kraus wrote his master thesis "Selbstreproduktion bei Programmen" (self-reproduction of programs)
* A program called Elk Cloner, written for Apple II systems and created by Richard Skrenta. Apple II was seen as particularly vulnerable due to the storage of its operating system on floppy disk. Elk Cloner's design combined with public ignorance about what malware was and how to protect against it led to Elk Cloner being responsible for the first large-scale computer virus outbreak in history.
* The term 'virus' is coined by Frederick Cohen in describing self-replicating computer programs. In 1984 Cohen uses the phrase "computer virus" to describe the operation of such programs in terms of "infection". He defines a 'virus' as "a program that can 'infect' other programs by modifying them to include a possibly evolved copy of itself."
* November 10, 1983, at Lehigh University, Cohen demonstrates a virus-like program on a VAX11/750 system. The program was able to install itself to, or infect, other system objects.
* January: The Brain boot sector virus (aka Pakistani flu) is released. Brain is considered the first IBM PC compatible virus, and the program responsible for the first IBM PC compatible virus epidemic. The virus is also known as Lahore, Pakistani, Pakistani Brain, as it was created in Lahore, Pakistan by 19 year old Pakistani programmer, Basit Farooq Alvi, and his brother, Amjad Farooq Alvi.
* December 1986: Ralf Burger presented the Virdem model of programs at a meeting of the underground Chaos Computer Club in Germany. The Virdem model represented the first programs that could replicate themselves via addition of their code to executable DOS files in COM format.
* Appearance of the Vienna virus, which was subsequently neutralized--the first time this had happened on the IBM platform.
* Appearance of Lehigh virus, boot sector viruses such as Yale from USA, Stoned from New Zealand, Ping Pong from Italy, and appearance of first self-encrypting file virus, Cascade. Lehigh was stopped on campus before it spread to the wild, and has never been found elsewhere as a result. A subsequent infection of Cascade in the offices of IBM Belgium led to IBM responding with its own antivirus product development. Prior to this, antivirus solutions developed at IBM were intended for staff use only.
* October: The Jerusalem virus, part of the (at that time unknown) Suriv family, is detected in the city of Jerusalem. Jerusalem destroys all executable files on infected machines upon every occurrence of Friday the 13th (except Friday 13 November 1987 making its first trigger date May 13, 1988). Jerusalem caused a worldwide epidemic in 1988.
* November: The SCA virus, a boot sector virus for Amigas appears, immediately creating a pandemic virus-writer storm. A short time later, SCA releases another, considerably more destructive virus, the Byte Bandit.
* December: Christmas Tree EXEC was the first widely disruptive replicating network program, which paralysed several international computer networks in December 1987.
* June: The Festering Hate Apple ProDOS virus spreads from underground pirate BBS systems and starts infecting mainstream networks.
* November 2: The Morris worm, created by Robert Tappan Morris, infects DEC VAX and Sun machines running BSD UNIX connected to the Internet, and becomes the first worm to spread extensively "in the wild", and one of the first well-known programs exploiting buffer overrun vulnerabilities.
* October 1989: Ghostball, the first multipartite virus, is discovered by Friðrik Skúlason.
* Mark Washburn working on an analysis of the Vienna and Cascade viruses with Ralf Burger develops the first family of polymorphic virus: the Chameleon family. Chameleon series debuted with the release of 1260.
* Michelangelo was expected to create a digital apocalypse on March 6, with millions of computers having their information wiped according to mass media hysteria surrounding the virus. Later assessments of the damage showed the aftermath to be minimal.
* "Leandro & Kelly" and "Freddy Krueger" spread quickly due to popularity of BBS and shareware distribution.
* The "Concept virus", the first Macro virus, is created which attacked Microsoft Word documents.
* "Ply" - DOS 16-bit based complicated polymorphic virus appeared with built-in permutation engine.
* June 2: The first version of the CIH virus appears.
* Jan 20: The Happy99 worm invisibly attached itself to emails. Displayed fireworks to hide changes being made and wished you a happy new year. Modified system files related to Outlook Express and Internet Explorer on Windows 95 and Windows 98.
* March 26: The Melissa worm is released, targeting Microsoft Word and Outlook-based systems, and creating considerable network traffic.
* June 6: The ExploreZip worm, which destroys Microsoft Office documents, is first detected.
* December 16: Sub7, or SubSeven, is the name of a popular backdoor program. It is mainly used for causing mischief, such as hiding the computer cursor, changing system settings or loading up pornographic websites. However, it can also be used for more serious criminal applications, such as stealing credit card details with a keystroke logger.
2000 and later
* May: The ILOVEYOU worm appears. As of 2004 this was the most costly virus to businesses, causing upwards of 5.5 to 10 billion dollars in damage. The backdoor trojan to the worm, Barok, was created by Filipino programmer Onel de Guzman; it is not known who created the attack vector or who (inadvertently?) unleashed it; de Guzman himself denies being behind the outbreak although he suggests he may have been duped by someone using his own Barok code as a payload.
* May 8: The Sadmind worm spreads by exploiting holes in both Sun Solaris and Microsoft IIS.
* July: The Sircam worm is released, spreading through Microsoft systems via e-mail and unprotected network shares.
* July 13: The Code Red worm attacking the Index Server ISAPI Extension in Microsoft Internet Information Services is released.
* August 4: A complete re-write of the Code Red worm, Code Red II begins aggressively spreading onto Microsoft systems, primarily in China.
* September 18: The Nimda worm is discovered and spreads through a variety of means including vulnerabilities in Microsoft Windows and backdoors left by Code Red II and Sadmind worm.
* October 26: The Klez worm is first identified.
* Beast is a windows based backdoor trojan horse, more commonly known in the underground cracker community as a RAT (Remote Administration Tool). It is capable of infecting almost all Windows OS i.e. 95 through XP. Written in Delphi and Released first by its author Tataye in 2002, it's most current version was released October 3, 2004
* August 30: Optix Pro is a configurable remote access tool or Trojan, similar to SubSeven or BO2K.
* January 24: The SQL slammer worm, aka the Sapphire worm, attacks vulnerabilities in Microsoft SQL Server and MSDE and causes widespread problems on the Internet.
* April 2: Graybird is a Trojan also known as Backdoor.Graybird.
* June 13: ProRat is a Turkish-made Microsoft Windows based backdoor trojan horse, more commonly known as a RAT (Remote Administration Tool).
* August 12: The Blaster worm, aka the Lovesan worm, rapidly spreads by exploiting a vulnerability in system services present on Windows computers.
* August 18: The Welchia (Nachi) worm is discovered. The worm tries to remove the blaster worm and patch Windows.
* August 19: The Sobig worm (technically the Sobig.F worm) spreads rapidly through Microsoft systems via mail and network shares.
* October 24: The Sober worm is first seen on Microsoft systems and maintains its presence until 2005 with many new variants. The simultaneous attacks on network weakpoints by the Blaster and Sobig worms cause massive amounts of damage.
* Late January: MyDoom emerges, and currently holds the record for the fastest-spreading mass mailer worm.
* March 19: The Witty worm is a record-breaking worm in many regards. It exploited holes in several Internet Security Systems (ISS) products. It was the fastest disclosure to worm, it was the first internet worm to carry a destructive payload and it spread rapidly using a pre-populated list of ground-zero hosts.
* May 1: The Sasser worm emerges by exploiting a vulnerability in LSASS and causes problems in networks, even interrupting business in some cases.
* August 16: Nuclear RAT (short for Nuclear Remote Administration Tool) is a backdoor trojan horse that infects Windows NT family systems (Windows 2000, XP, 2003).
* August 20: Vundo, or the Vundo Trojan (also known as Virtumonde or Virtumondo and sometimes referred to as MS Juan) is a Trojan horse that is known to cause popups and advertising for rogue antispyware programs, and sporadically other misbehavior including performance degradation and denial of service with some websites including Google and Facebook.
* October 12, 2004: Bitfrost, also known as Bitfrose, is a backdoor trojan which can infect Windows 95 through Vista. Bifrost uses the typical server, server builder, and client backdoor program configuration to allow a remote attack.
* December: Santy, the first known "webworm" is launched. It exploited a vulnerability in phpBB and used Google in order to find new targets. It infected around 40000 sites before Google filtered the search query used by the worm, preventing it from spreading.
* August 16: The Zotob worm and several variations of malware are discovered on Microsoft systems. The effect was overblown because several United States media outlets were infected.
* October 13: The Samy XSS worm becomes the fastest spreading virus by some definitions as of 2006.
* October 31: Sony BMG was found to have purposefully infected music CDs with a rootkit in an attempt to prevent illegal copying of music.
* Late 2005: The Zlob Trojan, also known as Trojan.Zlob, is a trojan horse which masquerades as a required video codec in the form of ActiveX. It was first detected in late 2005.
* 2005: Bandook or Bandook Rat (Bandook Remote Administration Tool) is a backdoor trojan horse that infects the Windows family. It uses a server creator, a client and a server to take control over the remote computer. It uses process hijacking / Kernel Patching to bypass the firewall, and allow the server component to hijack processes and gain rights for accessing the Internet.
* January 20: The Nyxem worm was discovered. It spread by mass-mailing. Its payload, which activates on the third of every month, starting on February 3, attempts to disable security-related and file sharing software, and destroy files of certain types, such as Microsoft Office files.
* February 16: discovery of the first-ever malware for Mac OS X, a low-threat trojan-horse known as OSX/Leap-A or OSX/Oompa-A, is announced.
* Late September: Stration or Warezov worm first discovered.
* January 17: Storm Worm identified as a fast spreading email spamming threat to Microsoft systems. It begins gathering infected computers into the Storm botnet. By around June 30 it had infected 1.7 million computers, comprised between 1 and 10 million computers by September. Thought to have originated from Russia, it disguises itself as a news email containing a film about bogus news stories asking you to download the attachment which it claims is a film.
* January 17: MacSweeper is the first known rogue software for Mac OS X.
* February 17: Mocmex is a trojan, which was found in a digital photo frame in February 2008. It was the first serious computer virus on a digital photo frame. The virus was traced back to a group in China.
* March 3: Torpig, also known as Sinowal and Mebroot, is a Trojan horse which affects Windows, turning off anti-virus applications. It allows others to access the computer, modifies data, steals confidential information (such as user passwords and other sensitive data) and installs more malware on the victim's computer.
* May 6: Rustock.C, a hitherto-rumoured spambot-type malware with advanced rootkit capabilities, was announced to have been detected on Microsoft systems and analyzed, having been in the wild and undetected since October 2007 at the very least.
* July 6: Bohmini.A is a configurable remote access tool or trojan that exploits security flaws in Adobe Flash 9.0.115 with Internet Explorer 7.0 and Firefox 2.0 under Windows XP SP2.
* July 31: Koobface is a computer worm that targets the users of the social networking websites Facebook and Myspace.
* January: Computer worm Conficker infects nearly 20 million Microsoft server systems running everything from Windows 2000 to the Windows 7 Beta and Windows Server 2000 & Windows Server 2008. French air force, Royal Navy warships and submarines, Sheffield Hospital network, UK Ministry of Defence, German Bundeswehr and Norwegian Police were all affected. Microsoft has allocated $250,000 to identify its creator. The worm is set to activate on April 1st, 2009, to look for updates whose objectives are currently unknown.