Security experts are urging users of Symantec's antivirus software to update it to combat a new variant of the worm known as either Rinbot or Delbot.

The worm exploits a vulnerability in Symantec software and seeks to set up botnets from which DOS (denial-of-service) attacks can be launched. It propagates by creating emails with the worm program attached or by attaching the program to outgoing email...