"We recently received reports about private messages found on Facebook and distributing a link, which is a shortened URL pointing to an archive file May09-Picture18.JPG_www.facebook.com.zip," Trend Micro researchers warn. "This archive contains a malicious file named May09-Picture18.JPG_www.facebook.com and uses the extension .COM."
Once the file is run and the worm gains a foothold in the system, it first tries to find and disable antivirus software in order to avoid detection. Then, it contacts a number of websites, and downloads from them another worm.
This one is capable of recording the users' browsing activity, as well as the contents of messages they send and receive through a number of social networking sites such as Facebook, Twitter and Meebo.
It is also capable of propagating itself by posting messages on the users' accounts containing an URL that leads to its copy.