The SANS Internet Storm Centre is estimating at least 700,000 computers have been infected by the 'Black' worm and on February 3 it will delete all documents.

Quo Vadis Limited vice president Stephen Davidson said: "We encourage residents to update their anti-virus software and run a complete systems scan before February 3 when the worm will begin deleting documents (Word, Excel, PDF's and a number of others)."

This worm is different and more serious from other worms for a number of reasons.

At this point, the worm will be detected by up to date anti virus signatures. In order to prevent data loss on February 3, residents should use current (January 23rd or later) anti virus signatures.

This worm/virus has collected a number of names from various vendors. It is so far known as Blackmal, Nyxem, MyWife, Tearec among other names.

The worm spreads via e-mail attachments or file shares. Once a system is in a network is infected, it will try to infect all shared file systems it has access to.

It will disable most anti virus products and delete them. The worm will e-mail itself using a variety of extensions and file names. It will add itself to the list of auto-start programs in a user's registry.

A special Storm Center website on the problem can be found at www.isc.sans.org/blackworm.