Security researchers have identified a new worm spreading across Yahoos instant messaging network that has been cloaked under the guise of a "safety" browser in an attempt to dupe users.
First discovered by anti-malware researchers at FaceTime Communications, the worm, labeled as yhoo32.explr, is forwarding itself throughout Yahoos IM system via the contact lists of people whose computers it has already been infected. Once loaded onto a PC, the malicious program automatically hijacks the computers existing browser home page and encourages users to visit a fraudulent Web site that attempts to load spyware programs onto their devices.
FaceTime researchers said they have observed two versions of the attack, one of which is a stand-alone application with no uninstaller that frequently disguises itself with a faked version of Microsofts Internet Explorer logo. The second, self-propagating iteration of the worm, uses an .exe file to spread the infection through the Yahoo Messenger directories.
Yahoo representatives didnt immediately return calls seeking comment on the IM virus.
In addition to prompting users to visit the malware-loaded Web site, the virus also plays looped guitar music whenever someone starts up a PC it has infected, or opens the fraudulent safety browser itself. FaceTime researchers said that the attack is the first form of virus they have encountered that installs its own Web browser on a PC without the users permission.
FaceTime officials said that the worm was first discovered by the India-based arm of its Security Labs division using a so-called honeypot trap designed specifically to attract malware code. The threats ability to take over a users browser without any specific interaction on the users part makes it very unique, company officials said.
"This is one of oddest and more insidious pieces of malware we have encountered in years," Tyler Wells, senior director of research at FaceTime Security Labs, said in a statement. "This is the first instance of a complete Web browser hijack without the users awareness."
Wells indicated that the existence of the new worm and similar rogue browsers, such as the previously identified Yapbrowser attack, prove that the malware writers are adapting to the use of security programs, and he predicted that there will be more of the sophisticated threats.
Much in the style of phishing schemes, the Web site linked to the yhoo32.explr virus appears to be legitimate, using Explorer logos that look very much like the real thing. Mirroring a trend that threatened the anti-virus industry several years ago, attacks that mimic the same types of applications that are used to defeat them are becoming increasingly popular in the spyware community. Experts have tabbed the technique as an attempt to cash in on the growing awareness of online threats and their links to offline identity fraud.
In a report issued in mid-May, security researchers at Finjans Malicious Code Research Center highlighted the growth of fake anti-spyware applications that promise to help scan for and delete malicious code. Once downloaded onto a users computer, the applications may deliver their own virus payloads or expose affected machines to subsequent attacks.
In some cases, said Yuval Ben-Itzhak, chief technology officer at Finjan, the false anti-spyware tools even run fake computer security scans that claim to find existing spyware programs on infected devices. The software then directs the computers user to a Web site where the user is encouraged to purchase a full version of the free application already on the PC.
"This is just more evidence of the level of professionalism among the people writing the attacks, who are likely involved with organized crime," said Ben-Itzhak. "You can imagine that these types of people will continue to try and disguise malicious programs specifically to appear like the types of programs other people are building to defeat them."