Internet Worm
Famous attack dating from 1988, which shut down a considerable portion of the then-existing internet. The Internet Worm exploited known security gaps in order to infect computers, broke through their password protection, and distributed itself further by using the information it thus obtained. The Internet Worm led to security on the internet becoming a prioritized issue; establishment of the CERT (Computer Emergency Response Team), for instance, is attributable to the Internet Worm.