Yahoo IM Worm Hijacks Browsers, Plays Migraine Music

A worm running through Yahoo's instant messaging network is installing a browser of its own -- a first for IM malware -- that leads users to adware and spyware sites, several security firms said Monday.

The worm, dubbed "Yhoo32.explr" by IM security vendor FaceTime Communications on Friday and "Browaf" by Symantec on Monday, is installed when Yahoo users click on a malicious link embedded within an instant message.

Yhoo32.explr downloads and installed the so-called "Safety Browser," which adds an IE-like icon to the desktop, and when used, takes the unsuspecting to sites where their PCs are infected with adware and spyware. The worm also changes the home page of IE to point to Safety Browser's site.

To complicate things, Safety Browser doesn't post an Uninstall option in Windows' Add or Remove Programs Control Panel applet.

"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, in a statement."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."

Along with the bogus browser, the worm makes the PC blare out screeching music thick with bad guitar licks and drum solos. The headache-inducing noise plays every time the computer boots or Safety Browser launches.

Anti-virus vendors, such as Symantec, are working on signatures to detect the new Yahoo IM worm; FaceTime said that has already it updated its customers' software.