Yahoo News is running a story about how the recursion feature of open DNS servers can be used to launch massive distributed denial of service (DDoS) attacks:

First detected late last year, the new attacks direct such massive amounts of spurious data against victim computers that even flagship technology companies could not cope. In one of the early cases examined, the unknown assailant apparently seized control of an Internet name server in South Africa and deliberately corrupted its contents.

Name servers are specialized computers that help direct Internet traffic to its destinations. The attacker then sent falsified requests to the compromised directory computer, which unleashed overwhelming floods of amplified data aimed wherever the attacker wanted. Experts traced at least 1,500 attacks that briefly shut down commercial Web sites, large Internet providers and leading Internet infrastructure companies during a period of weeks. The attacks were so targeted that most Internet users did not notice widespread effects.

Ken Silva, the chief security officer for VeriSign Inc., compared the scale of attacks to the damage caused in October 2002 when nine of the 13 computer "root" servers that manage global Internet traffic were crippled by a powerful electronic attack. VeriSign operates two of the 13 root server computers, but its machines were unaffected. "This is significantly larger than what we saw in 2002, by an order of magnitude," Silva said. Silva said the attacks earlier this year used only about 6 percent of the more than 1 million name servers across the Internet to flood victim networks. Still, the attacks in some cases exceeded 8 gigabits per second, indicating a remarkably powerful electronic assault.