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 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.