Symantec is warning about a mass-mailing worm that comes in an attachment pretending to be a Twitter invite.
"The observed messages appear as if they have been sent from a Twitter account; however, unlike a legitimate Twitter message, there is no invitation URL present in the body," a Symantec blog post says. "Instead, the user will see an attachment that appears as a .zip file that purportedly contains an invitation card."
The name of the attachment is "Invitation Card.zip" and Symantec identified it as W32.Ackantta.B@mm, a worm targeting Windows computers that was discovered in an e-card virus attack in February, according to Symantec. The worm gathers e-mail addresses from compromised PCs and spreads by copying itself to removable drives and shared folders.