A new variant of the Klez worm was spreading Wednesday, security companies said.
The W32.Klez.H worm, like its predecessors, spreads via e-mail with random subject lines and attachments and tries to disable antivirus software, experts said.
The worm appeared to be spreading rapidly in Japan, China, Austria and the Czech Republic, according to Vigilinx, a Parsippany, N.J.-based security services firm.
Symantec gave Klez.H a threat rating of three on a scale of one to five, with five being the most serious. The vendor created a new virus definition to block the worm and urged customers to update their antivirus software.