A worm attached to an e-mail with the subject line "Happy New Year!" is the latest spam to threaten computer users, a security expert warns.

The new worm comes disguised as a file attachment named postcard.exe or postcard.zip, VeriSign iDefense Labs revealed on Thursday.

Once the file is launched, it replicates itself and sends copies to other e-mail addresses by accessing the infectedcomputer's mailbox. It also disables several computer security features and installs rootkit software, which allows it to hide itself from the user.

VeriSign said several large networks reported interceptions of the new e-mail on Thursday. Several other security firms also reported the virus. Kaspersky Lab dubbed the worm "Tibs" while Trend Micro calls it "Nuwar." Other names for it include Banwarum and Glowa.

Network sendsspam five times per second

The worm is reportedly being spread from 160 e-mail domains, with one network sending out the spam at a rate of five e-mails per second.

The "Happy New Year!" e-mail is just one variation on holiday spam. On Wednesday, security firm McAfee issued several warnings, including one for an e-mail with the attachment Christmas+Blessing-4.ppt, which installs software that allows the spammer remote access to the infected computer.

As with all e-mails, users should use extreme caution when opening attachments, VeriSign warns.