Computer Worm

A worm is a software parasite that can erase everything in sight. It replicates itself over and over and it can comsume memory, disk space or bandwith in the process. If left unchecked, a worm can destroy all necessary files a computer needs. Worms replicate often through a network. Unlike viruses, Worms usually do not infect other program on the host's machine.

The CHRISTMA worm spread at December 1987. It looks like an innocent digital Christmas card. When you open it this so called CHRISTMA exec sends the christmas card to everyone in your address book, causing the worm to spread further.

The Morris Worm was named after its creator, Robert Morris. It is uncertain if Morris's worm was released intentionally or unintentionally. According to the Computer Emergency Response Team(CERT), the Morris Worm crippled approximately 10% of all computers connected to the Internet.

BubbleBoy
The BubbleBoy worm surfaced in November 1999. BubbleBoy could be triggered by merely reading an infected email. Once unleashed, it attacked Microsoft Outlook users by mailing a copy of itself to everyone in the victim's email address book. Although widely hailed as the first of its kind, such unexpected behaviour was not completely without precedent.