Robert Morris unleashed the original computer worm (perhaps accidentally) on the Internet in 1988. The Internet Worm used sendmail, fingerd, and rsh/rexec to spread itself across the Internet.
The SQL Slammer Worm, which was founded in 2003, used a vulnerability in Microsoft SQL Server 2000 to spread itself across the Internet. The Blaster Worm, also founded in 2003, used a vulnerability in Microsoft DCOM RPC to spread itself.
The Melissa worm founded in 1999, the Sobig worms founded in 2003, and the Mydoom worm founded in 2004 all spread through e-mail. These worms shared some Trojan Horse features in that they spread by tempting a user to open an infected e-mail attachment.
Mydoom also attempted to spread itself through the peer-to-peer file sharing application called KaZaA. The Mydoom worms attempted a Denial of Service (DoS) attack against SCO and Microsoft.