A malicious advertisement has been found within an application for Facebook that redirected users to fake antivirus software, according to a security researcher.
The banner advertisement for greeting cards was intermittently displayed with an application called Farm Town, which has more than 9 million monthly users according to information published on Facebook.
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If the bad Shockwave Flash advertisement was displayed, the user was redirected from Facebook through several domains and ended up on a Web site selling fake antivirus software, said Sandi Hardmeier, who studies malicious advertisements and blogged about the issue.
Farm Town's developer, SlashKey, has a notice on its Web site saying it has notified its developers of the problem.
"We believe at this time that it is harmless to your computer and a result of one or more of the ads on the site, but you should not follow any links to any software claiming to 'clean your system,'" the notice reads. "Most good antivirus/malware program will catch and quarantine this malware."
Hardmeier disagrees that it is harmless. "I'm disappointed that they are trying to minimize the perception of risk," she said.
The bad advertisement has since been pulled, said Matt Brummett, account manager at Adknowledge, the online advertising network that owns Cubics.com, which served the ad. The agency that supplied Cubics.com with the ad, AdSeven Media, based in the Netherlands, has been banned from their network, Brummett said.
Brummett said Adknowledge uses both technical and other checks to keep out bad ads, but on rare occasions the safeguards are circumvented. "We have identified the breakdown on this occurrence, and it will be remedied," he said.
Fake antivirus sites usually tell users their computers are infected and implore them to download the software, which is often completely ineffective. Consumers are charged as much as $70 for the software, which is also difficult to remove, and have trouble recovering their money.
There are hundreds of fake antivirus programs, and security experts estimate it is a multimillion dollar industry. Panda Security wrote in a report last year that as many as 35 million computers worldwide may be infected with fake antivirus programs each month.
Google's Chrome browser did detect the malicious domains used to redirect the user and blocked the attack. The company has "safe browsing" technology built into its browser that will block users from going to potentially harmful Web sites. Internet Explorer 8, however, did not, Hardmeier said. She was in the process of testing Firefox on Monday morning.
Hackers have been known to figure out ways to slip their malicious advertisements onto ad networks that supply advertisements to innumerable Web sites. Many ad networks have taken steps to ensure malicious ads don't circulate. But there are ways around using the ad networks.
"The bad guys are going straight to site owners and offering them advertising," Hardmeier said via instant message. "The responsible networks are monitoring for the bad stuff and catching it and will suspend the bad campaigns immediately."
Hardmeier said she notified Cubics.com, which delivered the ad to Farm Town, and is in the process of notifying Facebook. Officials at Facebook could not be immediately reached.
Social networking sites such as Facebook are a prime target for scammers due to their high number of users and potential victims.