1. 1949
Theories for self-replicating programs are first developed.
1981
Apple Viruses 1, 2, and 3 are some of the first viruses “in the wild,” or in the public domain.
Found on the Apple II operating system, the viruses spread through Texas A&M via pirated
computer games.
1983
Fred Cohen, while working on his dissertation, formally defines a computer virus as “a computer
program that can affect other computer programs by modifying them in such a way as to include a
(possibly evolved) copy of itself.”
1986
Two programmers named Basit and Amjad replace the executable code in the boot sector of a
floppy disk with their own code designed to infect each 360kb floppy accessed on any drive.
Infected floppies had “© Brain” for a volume label.
1987
The Lehigh virus, one of the first file viruses, infects command.com files.
1988
One of the most common viruses, Jerusalem, is unleashed. Activated every Friday the 13th, the
virus affects both .exe and .com files and deletes any programs run on that day.
MacMag and the Scores virus cause the first major Macintosh outbreaks.
1990
Symantec launches Norton AntiVirus, one of the first antivirus programs developed by a large
company.
1991
Tequila is the first widespread polymorphic virus found in the wild. Polymorphic viruses make
detection difficult for virus scanners by changing their appearance with each new infection.
1992
1300 viruses are in existence, an increase of 420% from December of 1990.
The Dark Avenger Mutation Engine (DAME) is created. It is a toolkit that turns ordinary viruses
into polymorphic viruses. The Virus Creation Laboratory (VCL) is also made available. It is the first
actual virus creation kit.
1994
Good Times email hoax tears through the computer community. The hoax warns of a malicious
virus that will erase an entire hard drive just by opening an email with the subject line “Good
Times.” Though disproved, the hoax resurfaces every six to twelve months.
1995
Word Concept becomes one of the most prevalent viruses in the mid-1990s. It is spread through
Microsoft Word documents.
1996
Baza, Laroux (a macro virus), and Staog viruses are the first to infect Windows95 files, Excel,
and Linux respectively.
1998
Currently harmless and yet to be found in the wild, StrangeBrew is the first virus to infect Java
files. The virus modifies CLASS files to contain a copy of itself within the middle of the file's code

2. and to begin execution from the virus section.
The Chernobyl virus spreads quickly via .exe files. As the notoriety attached to its name would
suggest, the virus is quite destructive, attacking not only files but also a certain chip within infected
computers.
Two California teenagers infiltrate and take control of more than 500 military, government, and
private sector computer systems.
1999
The Melissa virus, W97M/Melissa, executes a macro in a document attached to an email, which
forwards the document to 50 people in the user's Outlook address book. The virus also infects
other Word documents and subsequently mails them out as attachments. Melissa spread faster
than any previous virus, infecting an estimated 1 million PCs.
Bubble Boy is the first worm that does not depend on the recipient opening an attachment in
order for infection to occur. As soon as the user opens the email, Bubble Boy sets to work.
Tristate is the first multi-program macro virus; it infects Word, Excel, and PowerPoint files.
2000
The Love Bug, also known as the ILOVEYOU virus, sends itself out via Outlook, much like
Melissa. The virus comes as a VBS attachment and deletes files, including MP3, MP2, and .JPG. It
also sends usernames and passwords to the virus's author.
W97M.Resume.A, a new variation of the Melissa virus, is determined to be in the wild. The
“resume” virus acts much like Melissa, using a Word macro to infect Outlook and spread itself.
The “Stages” virus, disguised as a joke email about the stages of life, spreads across the
Internet. Unlike most previous viruses, Stages is hidden in an attachment with a false “.txt”
extension, making it easier to lure recipients into opening it. Until now, it has generally been safe to
assume that text files are safe.
“Distributed denial-of-service” attacks by hackers knock Yahoo, eBay, Amazon, and other high
profile web sites offline for several hours.
2001
Shortly after the September 11th attacks, the Nimda virus infects hundreds of thousands of
computers in the world. The virus is one of the most sophisticated to date with as many as five
different methods of replicating and infecting systems. The “Anna Kournikova” virus, which mails
itself to persons listed in the victim's Microsoft Outlook address book, worries analysts who believe
the relatively harmless virus was written with a “tool kit” that would allow even the most
inexperienced programmers to create viruses. Worms increase in prevalence with Sircam,
CodeRed, and BadTrans creating the most problems. Sircam spreads personal documents over
the Internet through email. CodeRed attacks vulnerable webpages, and was expected to eventually
reroute its attack to the White House homepage. It infected approximately 359,000 hosts in the first
twelve hours. BadTrans is designed to capture passwords and credit card information.
2002
Author of the Melissa virus, David L. Smith, is sentenced to 20 months in federal prison. The
LFM-926 virus appears in early January, displaying the message “Loading.Flash.Movie” as it
infects Shockwave Flash (.swf) files. Celebrity named viruses continue with the “Shakira,” “Britney
Spears,” and “Jennifer Lopez” viruses emerging. The Klez worm, an example of the increasing
trend of worms that spread through email, overwrites files (its payload fills files with zeroes), creates
hidden copies of the originals, and attempts to disable common anti-virus products. The Bugbear
worm also makes it first appearance in September. It is a complex worm with many methods of
infecting systems.
2003
In January the relatively benign “Slammer” (Sapphire) worm becomes the fastest spreading
worm to date, infecting 75,000 computers in approximately ten minutes, doubling its numbers every
8.5 seconds in its first minute of infection. The Sobig worm becomes the one of the first to join the
spam community. Infected computer systems have the potential to become spam relay points and

3. spamming techniques are used to mass-mail copies of the worm to potential victims.
2004
In January a computer worm, called MyDoom or Novarg, spreads through emails and file-sharing
software faster than any previous virus or worm. MyDoom entices email recipients to open an
attachment that allows hackers to access the hard drive of the infected computer. The intended
goal is a “denial of service attack” on the SCO Group, a company that is suing various groups for
using an open-source version of its Unix programming language. SCO offers a $250,000 reward to
anyone giving information that leads to the arrest and conviction of the people who wrote the worm.
An estimated one million computers running Windows are affected by the fast-spreading Sasser
computer worm in May. Victims include businesses, such as British Airways, banks, and
government offices, including Britain's Coast Guard. The worm does not cause irreparable harm to
computers or data, but it does slow computers and cause some to quit or reboot without
explanation. The Sasser worm is different than other viruses in that users do not have to open a file
attachment to be affected by it. Instead, the worm seeks out computers with a security flaw and
then sabotages them. An 18-year-old German high school student confessed to creating the worm.
He's suspected of releasing another version of the virus.