Some of the users who visited KickassTorrents (KAT), one of the most popular torrent trackers on the Internet, over the weekend had the nasty surprise of being infected with a rogue antivirus program called "Security Sphere 2012."
According to experts from Web security vendor Armorize Technologies who detected the drive-by download attack, the infection process did not require any user interaction if the victim had outdated browser plug-ins.
According to Alexa.com, kat.ph ranks 320 by global daily traffic and is among the top 500 websites in the U.S. By other compete.com estimates, the torrent index gets around 1.5 million unique visitors every month.
The attack was instrumented through malicious advertisements pushed onto the website via a compromised OpenX server. Webmasters deploy such servers to sell ad space directly instead of using standard advertising networks like Google's or Microsoft's.
At the time of the attack, the "Security Sphere 2012" scareware program had a very low antivirus detection rate and even worse, some users might have ignored the alerts they received from those anti-malware programs that did pick it up.
That's because one week before, a malware definition error resulted in avast! Antivirus incorrectly flagging kat.ph as infected. The KickassTorrent admins released a statement at the time to dismiss the alerts as a false positive incident and that bogus detection might have now led users to believe this was a similar problem.
Malvertizing (malicious advertising) attacks are much more dangerous than those relying on spammed links or social engineering because they exploit the trust relationship between users and their favorite websites. Coupled with drive-by download exploits like those used in this case, such incidents can result in a high number of victims.
Symantec has partnered with Armorize Technologies to develop a new cloud-based service called Symantec AdVantage, which promises to help webmasters detect malicious code hidden within the advertisements displayed on their websites.
"Malvertising poses a serious risk to online publishers and their customers, reputation and revenue. Highly publicized malvertising infections can damage the reputation of even the most trusted online sites," said Fran Rosch, vice president of identity and authentication services at Symantec.
In the past, websites and services like The New York Times, TweetMeme, Spotify, ICQ, Yahoo, Google, Bing, Al Jazeera, Tucows, The Pirate Bay, and many others have fallen victim to this kind of attack. Users can best protect themselves by keeping their software up to date, especially the browser plug-ins and operating system, and optionally using extensions like NoScript that block third-party scripts, including ads, by default.