Sober.X worm digs in

The Sober.X computer worm that began flooding inboxes last month masquerading as a threatening e-mail from federal investigators made a resurgence this week, with security experts now calling it the most prolific e-mail worm ever unleashed.

The junk traffic generated by Sober has bogged down e-mail systems at some of the nation’s largest Internet service providers. E-mail security company Postini Inc. said it had blocked more than 35 million Sober-generated messages on Tuesday alone.

The worm often comes attached to an e-mail supposedly sent by the FBI or CIA, claiming that the government has discovered you visiting “illegal” Web sites and asking you to open an attachment to answer some official questions. Microsoft Windows users who click on the attached file infect their computers with the worm, which then e-mails copies of itself to every address found on the victim’s machine.

To avoid computer infection, users need to delete the e-mail without opening the attachment.