A computer virus that was designed to start its malicious work on Friday did not cause the mayhem that was anticipated, computer security firms said. The worm, known as "Blackmal" and "Kama Sutra," hides inside email attachments and contains a time-activated payload due to execute on the third day of each month, first occurring on Friday.

Once activated, the worm will try to spread itself, attempt to stop anti-worm software from running and try to delete all Word, Excel, PowerPoint and PDF file types from an infected PC.

Rather than disabling up to 500,000 PCs that were expected to be infected, the virus had hit only a few thousand computers by midday in continental Europe, mostly from individual consumers, according to several computer security firms.

Advance warnings by virus security firms and enterprises to their customers and employees appeared to have worked.

"This is certainly not a disaster," said technical consultant Graham Cluley at British virus fighter firm Sophos.

Rival security software firm Symantec confirmed "the worm is not spreading wildly and infections are relatively low."

The virus is also known as "Nyxem," "MyWife," and "Tearec."