"It really preys on paranoia about the Sasser worm, " said Graham Cluley, senior technology consultant for Sophos.

CNN: Sasser worm rips through Internet

In a cunning twist by the virus writers, an e-mail in wide circulation that purportedly offers a "fix" for the Sasser worm actually infects the user's computer with a different virulent worm, known as Netsky-AC.

CNN: Sasser worm rips through Internet

"Sasser is a successful and widely propagating worm with a somewhat benign impact to the end user, " said Chris Rouland of Internet Security Systems.

CNN: Sasser worm rips through Internet