Hackers have developed an email worm that exploits interest in the World Cup in a bid to tempt football fans to open a malicious attachment.

The Sixem-A worm spreads using a variety of disguises, including subject lines such as 'Naked World Cup game set', 'Soccer fans killed five teens' and 'Crazy soccer fans', to try and dupe unsuspecting users into clicking on a malicious attachment.

One of the messages sent by the worm reads: 'Nudists are organising their own tribute to the world cup, by staging their own nude soccer game, though it is not clear how the teams will tell each other apart. Good photos ;)'

Other messages, some of which claim to come from the CNN news organisation, can include: 'Soccer fans killed five teens, watch what they make on photos. Please report on this all who know.'

If the attached file is run, it attempts to disable security software on the infected computer and then spread itself to other email addresses.

"This worm exploits the public's interest in the World Cup to infect business users," said Graham Cluley, senior technology consultant at Sophos.

"While some recipients might find nude football an attractive prospect, this is one worm you don't want to catch sight of as you'll be playing straight into the hands of hackers.

"It is very likely that more internet criminals will take advantage of users' football fever as the tournament heats up, so people need to wise up to security threats or risk scoring an own goal."

This is not the first time hackers have taken advantage of the World Cup. A year ago, the Sober-N worm offered tickets to the tournament in an attempt to entrap unprotected users, while in 2002, the Chick-F virus tried to exploit workers desperate to find out the latest scores from the World Cup in S Korea/Japan.

In 1998, in the run-up to the World cup competition in France, another football-inspired virus asked infected victims to gamble on who the winner might be.

If the user did not choose the right team the virus triggered a warhead that was capable of wiping all the data off the hard drive.