Worst Computer Viruses Part 5

Aug 9, 2017 | Blog, IT Services

Part five of some of the worst computer viruses, Trojans and Malware to ever infect computers and networks on a massive level.

Mobile Virus ProtectionZeus

A Trojan horse malware package that runs on versions of Microsoft Windows often used to steal banking information by man-in-browser keystroke logging and form grabbing.


A computer worm which exploits security vulnerabilities in Microsoft operating systems. It’s been estimated that the Zotob worm costs an average of $97,000 and 80 hours of cleanup per company affected.


Modular computer malware that attacks computers running Microsoft Windows operating system. The program is being used for targeted cyber espionage in Middle Eastern countries.


A modular computer virus used for cyber espionage in the energy sector that can spread from an infected machine to other computers on the network. Upon infection, the virus compiles a list of files, uploads them to the attacker and then erases them.


Malware toolkit that targets specific users of Microsoft Windows-based computers. The malware’s main victims are private individuals, small businesses, and telecom companies.


A DOS-based polymorphic computer virus that encrypts two unencrypted cylinders of the user’s hard disk but then temporarily decrypts them when they are accessed, making sure the user does not notice that their hard disk is being encrypted.


A boot sector virus that becomes active if a disk access is made exactly on the half-hour and start to show a small “ball” bouncing around the screen in both text mode and graphical mode. No series damage occurs, however, some machines would crash during the ball’s appearance on the screen.

Christmas Tree EXEC

The first widely disruptive computer worm which paralyzed several international computer networks in December 1987. The user is prompted to “just type Christmas” which would launch the worm.

The Rabbit

A virus that makes multiple copies of itself on a single computer until it clogs the system, reducing system performance, before finally reaching a threshold and crashing the computer.

Creeper System

An experimental computer program originally designed to move between mainframe computers. The program was not actively malicious software as it caused no damage to data, the only effect being a message outputted to the teletype reading “I’m the creeper: catch me if you can.”

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