Yahoo IM worm hijacks Internet Explorer homepage

Stan Beer
Tuesday, 23 May 2006 08:47

Business IT - Security

Users of Yahoo Instant Messenger are under threat from a worm that hijacks their Internet Explorer homepage and leads them to a site that puts spyware on their PCs. Researchers at anti-malware firm FaceTime Security Labs, who identified the threat, say that the yhoo32.explr worm puts its own browser called Safety Browser on their PCs, the first recorded incidence of malware installing its own web browser on a PC without the user's permission.

According to FaceTime researchers, because Safety Browser uses the IE icon, users can easily mistake it for Internet Explorer.

A FaceTime alert says the self-propagating worm spreads the infection to Yahoo! Messenger contacts on the infected PC by sending a nefarious website link during a conversation. The link leads to a website that loads a command file onto the user’s PC and installs Safety Browser. This spam over instant messaging (IM) is called spim. IM applications and protocols are an increasingly popular vector to distribute malicious files and executables.

"This is one of oddest and more insidious pieces of malware we have encountered in years," said Tyler Wells, senior director of research at FaceTime Security Labs. "This is the first instance of a complete web browser hijack without the user's awareness. Similar 'rogue' browsers, such as 'Yapbrowser', have demonstrated the potential for serious damage by directing end-users to potentially illegal or illicit material. 'Rogue' browsers seem to be the hot new thing among hackers."

The India research arm of FaceTime Security Labs discovered the threat in a 'honeypot', a trap they set to detect viruses, worms, spyware and other threats. Commentary on this threat by FaceTime Security Labs researcher Chris Boyd can be found on the Greynets Blog, at http://blog.spywareguide.com.

The malware infects the PC with two elements.

The first element is a web browser called "Safety Browser." This stand-alone application has no uninstaller and disguises itself with an Internet Explorer logo in some instances. The application also hijacks the personal homepage in Internet Explorer and points users to Safety Browser's homepage (demoplanet.tv). The hijack also plays looped music that cannot be stopped when the user starts up the PC or Safety Browser.

The second element is the self-propagating worm. The worm propagates by inserting a link into existing Messenger conversations on an infected PC. When an infected user initiates or joins a conversation, a link is inserted at random points in the conversation.