One week after Facebook started showing off a security system it claimed could analyze up to 650,000 user actions per second, a scam was making the rounds on the 800-million-member social network.

“Halloween suicide thing on Facebook? Don't click unless you want to share a scammy survey,” Cisco Security warned Twitter followers.

The so-called “girl killed herself” scam is a new spin on an old trick, in which a salacious message links users to unrelated content. In this case, the message promises to show users something that prompted a girl to kill herself on Halloween after her father posted it on her wall. Users who click though on the link are taken to a third-party Web site which instructs them to giver permission to the Web site to share the link with their friends before they can see the content.

People who click through that final step -- and the fact that the links are spreading proves that people are -- they are told to choose a survey to complete, after which they’ll be able to see the video. Scammers earn commissions for each of the surveys they dupe people into filling out.

“unbelievable that people still think these are real...” Scott Clay tweeted.

Last week Facebook started releasing details about the Facebook Immunity System, which was presumably aimed at stopping messages like this from spreading through Facebook. The company claims FIS is capable of processing the 25 billion daily actions by users on Facebook, or 650,000 actions per second. The system was developed over a three-year period and, as a result, spam now affects less than 0.5 percent of its users. Facebook said last week that it now gets abuse reports from less than one percent of its users.

Facebook released details of the system, including the revelation that the system can learn in real time and does not need human direction to stop threats, during October, which is National Cybersecurity Month. But the release also comes less than two weeks before Nov. 5 -- the day the hacker group Anonymous has promised it would take down Facebook.

Photo by Ben Sutherland