With porn as its bait, the virus is set to corrupt files once a month after it gets inside a user's computer.
In its advisory for the Kama Sutra worm, otherwise known as win32/Mywife.E@mm and Nyxem.E, Microsoft warns users to be wary of opening unknown attachments.
The worm, which infects a user's computer once an attachment is opened, may also spread over writeable network shares if there are blank administrator passwords. Users hit with the worm may find a number of their files permanently corrupted on the third day of every month, beginning this Friday.
Like other worms, the Kama Sutra virus attempts to disable security software that is loaded on users systems, Microsoft warns.
Microsoft is advising users to update their antivirus software, as well as remain cautious when opening unknown attachments and use strong password protection.
Security experts estimate the worm has infected at least 500,000 PCs, often using pornography as its enticement.