Security experts today warned that a "widespread worm" posing as a Valentine's greeting is spreading fast across the internet.

Dref-AB has been deliberately spread so that office workers and home computer users find the malicious email in their inbox first thing this morning.

Since midnight GMT Dref-AB has accounted for 76.4 per cent of all malware sighted at Sophos' global network of virus monitoring stations.

Subject lines used in the attack are many and varied, but all pose as a romantic message. Some of them include: 'A Valentine Love Song', 'Be My Valentine', 'Fly Away Valentine', 'For My Valentine' and 'Happy Valentine's Day'.

The worm is attached to the emails in files called 'flash postcard.exe', 'greeting postcard.exe', 'greeting card.exe', or 'postcard.exe'.

"This new Valentine attack is spreading fast across the net, accounting for over three quarters of all the malware we've seen at email gateways around the globe since 14 February began," said Graham Cluley, senior technology consultant at Sophos.

"People will be truly love sick if they let the virus run on their PC."

Opening the attached files on a PC activates the worm, which then sends itself to other email addresses found on the infected computer.

Sophos believes that the worm's code is designed to download further malicious code from the internet in an attempt to take over the PC, convert it into part of a zombie network, and use it to send spam on behalf of hacking gangs.

"Cynical hackers are using the theme of Valentine's Day to conquer innocent people's computers and use them for their own money-making purposes," added Cluley.