Security experts are warning that a new variant of the mass-mailing worm "W.32Navidad" virus is now on the loose, and they say another worm that disguises itself as a Shockwave Flash movie is also becoming a problem.

Symantec’s antivirus research centre(http://www.sarc.com) initially reported the W.32Navidad worm, which affects Microsoft's Outlook email application, in early November.

The first W.32Navidad worm would launch only once and would insert itself in a reply to all email messages with attachments in the user's in-box. A new version has emerged, however, that launches each time the user activates the email program.

Reports are also emerging about TROJ_SHOCKWAVE.A - a new email spamming worm, now out in the wild.

The worm arrives in an email message with a line that reads, "A great Shockwave flash movie." It contains an attachment with the filename Creative.exe. The file size is 36,864 bytes.

When a user tries to view the movie attachment, the worm sends a copy of itself to all people in the address book of the user's Outlook program, potentially clogging email networks.