Football fans beware! The Sober worm is spreading like wildfire across Europe under the guise of free tickets to the 2006 World Cup Finals to entice people to click the infected attachment.

Once clicked, the worm spreads to other computers via e-mail and slows down the infected machine. No other side effects such as file deletions have been seen at this time.

"Many people will be eager to attend one of the biggest sporting events in the world next year, and may think its worth the risk of opening the e-mail attachment just in case the prize is for real. Computer users who don't practise safe computing will feel as sick as a parrot, and will only be passing this worm onto other unsuspecting victims," said Graham Cluley, senior technology consultant for Sophos.

The worm has spread at a faster pace over the past few days and now accounts for a staggering 4.5% of all e-mail sent across the Internet.

Graham Cluley continues, "One in every 22 e-mails sent across the Internet is currently infected by the Sober-N worm - making this one of the biggest virus outbreaks of the year."