Gigger, a new JavaScript-based virus, has escaped into the wild. It attempts to delete files from a computer and format user's disk drive on restart and antivirus vendors are characterising it as high-risk.

Gigger, which uses a combination of Microsoft Outlook and mIRC to spread, is not spreading widely, but its destructive potential has prompted Symantec to issue a strongly worded warning about the worm.

The virus attempts to pass itself off as a security update from Microsoft but the software giant always makes updated software available through its Web site, and never by email.

Gigger usually arrives with the subject line "Outlook Express Update" and an infected attachment "mmsn_offline.htm". Its author is believed to be Bulgarian.

Antivirus vendors are updating their software to detect the virus and protection is now largely in place. ®