Which of the following is a computer worm that caused a denial of service on some Internet hosts and dramatically slowed down general Internet traffic?

Code Red was a 2001 worm that targeted Microsoft IIS web servers, primarily defacing websites and launching DDoS attacks against specific IP addresses, not broadly slowing Internet traffic through mass propagation.

Beast was a remote access Trojan (RAT) designed for client-side backdoor access, not a self-propagating worm capable of causing widespread Internet slowdowns.

SQL Slammer exploited a buffer overflow vulnerability (MS02-039) in Microsoft SQL Server's resolution service on UDP port 1434. It was a 376-byte worm that replicated so rapidly it doubled in size roughly every 8.5 seconds, saturating network bandwidth and causing packet loss and DoS conditions across major Internet infrastructure within minutes of release in January 2003.

Klez was an email-borne worm and virus that spread via attachments and exploited Outlook vulnerabilities, known for mass-mailing and file infection rather than network-level denial of service.