A variant of the Melissa A virus – Melissa W - could pose a threat to users of Office 2001 for the Mac.

Melissa W bypasses detection software due to an altered file-format. However, Symantec, developers of Norton AntiVirus for Macintosh, expects to have a fix for the Melissa W virus today (Friday).

This macro virus is based on the Melissa A virus, which infected Word '97 documents, with files becoming infected when the "Document–Open" or "Document_Close" routine is used. The virus displays a number of randomly coloured and sized objects, and also can reformat the infected system's hard drive.

Symantec is developing a patch to Melissa's engine that will block the virus. Norton AntiVirus can currently detect the Melissa W virus, but is unable to destroy it.

McAfee, which develops anti-virus software, has received 20 reports of the virus striking within the past 48 hours.

Computer analysts recommend deleting any suspicious email prior to opening, especially if they read "Important Message From…" in the heading and, in the body, "Here's that document you asked for ... don't show anyone else ;-)."