E-mail users are receiving an increasing number of bounceback spam, known as backscatter, and security experts say this kind of spam is growing

The bounceback email messages come in at a trickle, maybe one or two every hour. The subject lines are disquieting: "Cyails, Vygara nad Levytar," "UNSOLICITED BULK EMAIL, apparently from you."

You eye your computer screen; you're nervous. What's going on ? Have you been hacked? Are you some kind of zombie botnet spammer? Nope, you're just getting a little backscatter -- bounceback messages from legitimate e-mail servers that have been fooled by the spammers.

Spammers like to put fake information in their e-mail messages in order to sneak them past e-mail filters. Because e-mail filters now just delete messages that come from nonexistent domains, the spammers like to make their messages look like they come from real e-mail addresses. That means, if your e-mail address has been published on the Web somewhere, you're a prime candidate for backscattering.