As with last year's "Code Red" episodes, the Apache/mod_ssl worm -- also called linux.slapper.worm and bugtraq.c worm -- looks for vulnerable computers in which it can place copies of itself, said Marty Lindner, team leader for incident handling at CERT, part of Carnegie Mellon University's Software Engineering Institute.

Unlike last year, however, the Apache worm's search generates far less traffic than the logjam that slowed the Web's overall performance during Code Red, Lindner told United Press International.

"System administrators should be looking out for traffic that matches the criteria described in our advisory," Lindner said. "If they see it, they should ...