The top 10 computer viruses, as compiled by news.com.au.
1. Jerusalem (1987)
This was one of the earliest and most successful viruses, which activated each Friday the 13th. The virus installed itself in the target computer's memory when an infected file was opened.
2. Stoned (1987)
This was apparently the biggest virus in terms of infections. The most common effect was to display a message that read: "Your PC is now stoned. Legalise marijuana." There are more than 90 variants of the virus, which miraculously resurfaced last year.
3. Tequila (1991)
Tequila infected computers by writing an unencrypted copy of itself to sectors of the system’s hard disk and modifying the master boot record. It was particularly dangerous as it used stealth methods to avoid detection and couldn't be removed from the infected computer's memory.
4. Michelangelo (1991)
Michelangelo was a sleeper. After spreading quietly for months, it activated on 6 March 1991 – the birth date of its namesake – destroying data on tens of thousands of computers by overwriting parts of the hard disk with random data.
5. ILOVEYOU (2000)
Known as the most destructive worm of all time, ILOVEYOU disguised itself as a romantic message to the recipient that, if opened, would send itself to everyone in the user's address book. ILOVEYOU reached up to 45 million people in one day, clogging email systems from the Pentagon to British Parliament.
6. Monopoly (2000)
The Monopoly worm sent itself by email, boasting "proof" that Microsoft boss Bill Gates was guilty of abusing his monopoly position. When opened, an image of Gates on a Monopoly game board was displayed. The worm then attempted to mass-mail itself to all of the user's contacts.
7. AnnaKournikova (2001)
This worm leveraged the popularity of tennis star Anna Kournikova. Once opened, the worm copied itself to the Windows directory and sent the file to all contacts in the user's address book. Email systems around the world were flooded.
8. Nimda (2001)
Nimda took the worm modus operandi a step further. As well as copying and emailing itself, the Nimda worm also moved across servers, infecting shared network hard drives and downloading itself to users who were browsing websites hosted on infected servers. This worm hit so hard the entire internet slowed down.
9. Sasser (2004)
This worm was created by a German teenager and caused some computers using Windows XP and Windows 2000 systems to continually crash and reboot. Sasser caused disruption worldwide; in Australia, Railcorp trains were forced to stop as operators couldn't communicate with signalmen. In Taiwan, over 400 post office branches were forced to revert to using pen and paper.
10. Storm (2007)
Known as a superworm, Storm is famous for the way it constantly morphs and continues to wreak havoc. Last year it infected thousands of computers by masquerading as an email about a weather disaster, and then mutated and spread with another fake attachment infecting 10 million computers.
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