Anti-virus experts are watching a new worm that spreads through Microsoft Corp.'s MSN Messenger client. The worm is not harmful to infected machines and has infected only a few PCs at this point, according to an analysis by Trend Micro Inc. Known as Jitux, the worm is self-propagating and contains a link to a Web site that automatically downloads an executable file named "jituxramon.exe" to the PC. Once the file runs, the worm begins sending out copies of itself to all of the names in the user's Messenger contact list. The worm, first discovered Tuesday, is capable of spawning multiple instances of itself on one PC. As of late Wednesday morning, Trend Micro had seen just a handful of infections, all outside the United States. Other anti-virus vendors have yet to develop descriptions or analyses of the worm.