"WM/PolyPoster Virus Steals User Documents And Posts Them on Usenet Newsgroup Boards"

This one's a bit bizarre (and I am not sure it affects Macs) but here it is (thanks, Monty Solomon):

"Data Fellows, one of the world's leading data security development companies, has discovered an important new macro virus known as WM/PolyPoster.

The new virus uses advanced replication methods to spread within Microsoft Word documents. Once a machine becomes infected by the virus, all Word documents manipulated in it will become infected and the virus will spread within them to new machines.

However, the most disturbing part of the virus is in it's activation routine. The virus activates at random times, and will try to send the user's Word documents to Usenet newsgroups. As an end result, the virus could post, for example, company confidential data or highly personal material in an open cyber-forum."

More details are on the Data Fellows web page.

Update: It appears that Mac users are not vulnerable to this attack. Michael Maggard writes: "The PolyPoster Word virus is Windows specific - it relies on the Window's Agent or Free Agent newsreading software to do its newsgroup posting." However, the principle behind the virus does not seem Windows-specific. A futurevariation of this type of virus could potentially affect the Mac. But we are safe for now.