Several banner ads containing Trojan horse programs that can compromise a user's computer have been running on some high-traffic Web sites for the past several weeks, including MySpace.com and Photobucket.com, Security Fix has learned.
Web security company ScanSafe said it first spotted the tainted banner ads on Aug. 8, and estimates that the hostile ads ran several million times for the next three weeks. Other sites that ran the ads included Bebo.com, TheSun.co.uk, and UltimateGuitar.com, officials at ScanSafe said. All a visitor to one of these sites needed to do to infect their machines was to browse a page that featured the ads with a version of Internet Explorer that was not equipped with the latest security updates from Microsoft.
This is hardly the first time malicious software has shown up in banner ads. A little over a year ago, I wrote about a similar banner ad attack that installed spyware on machines of more than a million MySpace.com users. This latest attack won't be the last either: Hacked banner ads are a very efficient way to distribute malware because they end up running on sites that most people trust:
The banner ads in question were traced back to an ad network exchange run by a company called RightMedia, which was recently bought by Yahoo!. The ads were being delivered to RightMedia's network from a third-party ad server. According to ScanSafe, those third-party servers included in their rotation several malicious ads that used Macromedia Flash files to load an invisible "iFrame" (used to insert content from another Web site into the current Web page). [...]
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Brian Krebs on Computer Security. The Washington Post Company