Morris worm

A famous occurrence of Internet sabotage. On November 2, 1988, Robert Morris, a Cornell University graduate student, unleashed a worm on the Internet that infected between 6,000 and 9,000 computers, overloading the entire Internet and causing many servers to fail as a result. As a computer science student, he was interested in determining how far and how quickly the worm could spread throughout the network, but he did not anticipate that it would cause as much trouble as it did due to his own misjudgment in coding the program's logic.

Morris was convicted and sentenced to three years of probation and 400 hours of community service as well as a $10,000 fine. This was a seminal incident in the history of Internet security that led directly to the founding of the CERT/CC a month later. See CERT, worm and denial of service attack.