Most Malicious Computer Viruses of All Time

ABC, discovered in October 1992, is a memory-resident, file-infecting computer virus which infects EXE files and may alter both COM and EXE files. ABC activates on the 13th day of every month.

The Ambulance virus infects practically all .COM files on the machine, and randomly runs the ambulance payload across the bottom of the screen when they are executed.

The Anna Kournikova computer worm was a computer worm written by a Dutch programmer named Jan de Wit on February 11, 2001. It was designed to trick email users into opening a mail message purportedly containing a picture of the tennis player Anna Kournikova, while actually hiding a malicious program

aka Norvarg, Mimail.R, Shimgapi, W32.MyDoom@mm

Mimicking an e-mail delivery failure notice, MyDoom sent e-mails that appeared to be from mailer-daemon. The e-mail contained an attachment, which unleashed the virus when opened.

The Sobig worm read documents on the infected computers’ hard drives to find e-mail addresses, then sent a copy of itself to those addresses.

The Sasser virus is a pain in the ass to get rid of. Computers infected with Sasser would shut themselves down and reboot continuously, with very little time between shutdowns, making it extremely difficult to remove.

The ILOVEYOU virus was one of the first to spread by e-mail. When unsuspecting users clicked on the attachment, it spread by infecting audio, image, and executable files on the infected computer.

The Blaster virus exploited a security hole in Windows that had been recently announced by Microsoft. Apparently, the author of the virus wanted to send Bill Gates a message.

The Conficker virus created a lot of havoc in the UK. The French Navy’s computer network has to be quarantined, which resulted in several grounded flights.

Sircam infected files on the affected computers and distributed them to the e-mail addresses in the host’s contact list. The files that were sent were usually Word or Excel files, often containing the victim’s personal information.

Code Red is another virus that exploits a weakness in Microsoft’s software, this time targeting the IIS Web Server software. The virus would display the message “Welcome to worm.com! Hacked by Chinese!” on the websites handled by the infected software, then use the server to find other computers running the same software.

This worm doesn’t exist on the infected computers’ hard drives. It runs from memory, which means that it leaves no trace and is wiped out completely by a simple reboot. Still, it took just 15 minutes for the SQL Slammer worm to spread throughout the world

The Melissa virus sent out e-mails with the message, “Here is that document you asked for … don’t show anyone else.” A Word document containing the virus was attached to the e-mail. The virus deleted critical Windows files in the affected computers and inserted random quotes from the Simpsons into files on t

The Nimda virus is spread through an e-mail attachment named README.EXE. It usually comes in an e-mail that has no subject or text. The virus can also be contracted by visiting an infected website, in which case, a readme.eml file will be downloaded onto the target computer.

The CIH virus infects every executable file that is accessed on the infected computer. The virus hides itself by writing its code into empty spaces in the files. The virus has a payload that is delivered each year on the author’s birthday, April 26th.