The biggest attack in years on the Internet's backbone servers, which slowed traffic but failed to bring down the Web, used infected computers around the world as "zombies," security experts said Wednesday.
Graham Cluley, senior technology consultant at the London-based firm Sophos, said Tuesday's incident "seems to have been the most serious attack against these domain name servers since December 2002."
Cluley said three of the 13 domain name system (DNS) servers that control global Internet traffic were hit with a so-called "denial of service" attack, which means they were bombarded with information requests in an effort to bring them down.
He said that since the 2002 attacks, "the system has become more resilient and is well set up to bounce back from these attacks."
Mike Poor at the US-based SANS Internet Storm Center said experts at the computer security institute were "aware of the attacks," and trying to get more information about them.
Cluley said a big part of the attacks was linked to so-called "zombie" computers that are infected by spam e-mails, leaving them open to control by hackers.
He said some reports traced the attacks to South Korea, but added that "it doesn't mean the hackers are based there ... the bad guys could be based anywhere in the world."