The worm spreads via email, and sits inside an attached Zip file. According to security firm iDefense, if the malicious attachment is executed, BugBear.E "performs a mass-mailing and installs a keylogger on the local system to steal sensitive information."
iDefense is warning that "considerable precautions are warranted due to the success and payloads of former BugBear variants." However, the company was unable to gauge the spread of the worm, as it is not yet detected by anti-virus software, and the outbreak has just begun.
For more information on BugBear.E, along with details on how to identify and remove it, see the Defense BugBear.F security alert.