AVERT, the Anti-Virus Emergency Response Team, a division of NAI Labs at Network Associates Inc. (NETA), has ranked the new strains as medium risk viruses.

Like their predecessor, the two new Melissas -- Melissa.U and Melissa V. -- arrive via an infected Word document e-mail attachment. The viruses have a subject line of "pictures" or "My Pictures", as well as the sender's username. The documents are marked with "Please Check Outlook Inbox Mail".

The virus infects Word's global template, NORMAL.DOT, and all future Word documents. Like the original Melissa, the address book is opened and the e-mail is re-sent to the first four e-mail addresses in the list, while the virus also attempts to erase several system files.

The original Melissa was created by David L. Smith, who allegedly stole an AOL user name to spread the macro virus and several others over the last year.