The Morris Worm
The Morris Worm or Internet Worm was a self-replicating computer virus written by Robert Tappan Morris, a student at Cornell University, and released from MIT on November 2, 1988. It took a great deal of hard work to get rid of this pesky digital virus from all the machines it had infected.
In the end, the United States Government Accountability Office estimates that the worm produced damages in the range of $100,000 to $10,000,000. And Morris himself was sentenced to three years in prison, 400 hours of community service and a $10,000 fine.