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A team of researchers has written a Facebook application for the social network that easily turned victims’ machines into bots able to wage distributed denial-of-service attacks (DDOS), as well as other malicious hacks.

The proof-of-concept Facebot application posed as Photo of the Day, a tool that displayed a different photo each day from National Geographic on users’ Facebook pages. But aside from serving up a photo, it was also serving up malware that recruited the victim’s machine into a botnet. The researchers -- mostly from the Institute of Computer Foundation for Research & Technology Hellas in Greece -- will present their findings at the upcoming Information Security Conference in Taiwan.

Facebot demonstrates just how simple it is to weaponize increasingly popular social networking applications for social networks such as Facebook’s, which can be written by anyone for the site. Security experts have warned that OpenSocial and other such social networking platforms are one of the weakest links on social networks. There are over 15,000 Facebook applications available to members today, according to the Facebot researchers. (See The Seven Deadliest Social Networking Hacks.)

Interestingly, the researchers did not invite users via Facebook to download the application, but still managed to attract around 1,000 users who downloaded Facebot within the first few days it went live. They merely announced its availability to members of their research group and asked them to pass it to their colleagues. From there it apparently spread to other Facebook users.

The application basically works like this: When a user clicks on the app, it displays a National Geographic image, and unbeknownst to the victim it also forces their machine to act as a bot and send out 600 Kbyte HTTP requests to other victims’ machines. The code instructed the bots to attack some computers in the researchers' lab.

“We have shown that applications that live inside a social network can easily and very quickly attract a large user-base (in the order of millions of users) that can be redirected to attack a victim host,” the researchers wrote in their paper. “We experimentally determined the user-base to be highly distributed, and of a world-wide scale.”

The researchers warn that the damage could be much more widespread than they demonstrated in their experiment, however. They set the app to limit the amount of attack traffic, but that doesn’t mean the bad guys will be so generous: “An adversary could employ more sophisticated techniques and create a JavaScript snippet, which continuously requests documents from a victim host over time. In this way the attack may be significantly amplified,” they wrote in their research paper.

And DDOS is only one type of attack a malicious Facebook app could execute, the researchers said. Other possible attacks include host scanning, malware propagation, and overriding authentication based on cookies. It also could execute targeted attacks on Facebook members, grabbing personal information on those who install the app, the researchers wrote.

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