Remember Melissa? It's been almost two years since that infamous worm swept through the world's email servers, spreading faster than any virus ever had before. Now there's a new variant.

Reports of the new strain, Melissa.W, started appearing midweek in Europe. By Thursday afternoon the Symantec Antivirus Research Center had upgraded the variant's severity rating to Category 4 (Severe).

Most of the first a/v update fixes will likely be definitions specific to Melissa.W. Some products can identify the new strain of the virus without yet repairing it.

The macro-based worm comes alive when you open an infected Word file, spreading to other documents and mailing itself as an attachment to the first 50 listings in your Microsoft Outlook address book. If one of the recipients opens the attachment, the cycle starts all over again.

An easy way to stop this is to turn off Word macros, of course. Don't open .exe files you don't know, and don't open Word files you're not expecting.

Subject lines to watch for

If you receive an e-mail message with a subject line that begins with "Important message from", be afraid.

If the body of the email message itself (and yes, you can safely open the message) tells you that "Here is that document you asked for ... don't show anyone else ;-)", be very afraid.

In fact, if you get such a message, delete it and notify the poor slob who accidentally sent it to you. And whatever you do, don't open the attached file.

The version of Melissa.W currently making the rounds is a Word 2001 file, something the antivirus programs aren't ready to handle. This version of Melissa is in fact a mutant.

Someone saved an infected file on a Mac - converting the file format and changing the nature of the virus - and then emailed it to a PC user.