Computer users opening emails with subject lines that claim they have won tickets to the World Cup in Germany have discovered all they won was a free computer virus.

A new variant of the infamous Sober worms, with bilingual German and English capabilities, is spreading on the Internet luring soccer fans into opening an infected attachment.

The email promises free tickets to the 2006 World Cup and, once opened, the virus invades the user’s email account to mass mail itself to others.

The virus, contained in attachments with addresses such as ticket@fifa.de or gewinn@fifa.de, has clogged up FIFA’s own system, disabling them to send emails.

Because the worm is compressed, antivirus programs cannot identify the worms.

According to Graham Cluley, senior technology consultant for London’s Sophos computer security firm, the worm can use a variety of different subject lines and message bodies.

“Many people will be eager to attend one of the biggest sporting events in the world next year, and may think it is worth the risk of opening the e-mail attachment just in case the prize is for real,” Cluley said.