Video scams are sweeping Facebook, encouraging users to click on a picture of a bikini-clad woman or a man being eaten by a snake.
One, headed "Look what this girl is wearing at the beach in front of thousands of people!", first emerged two years ago, but has recently reappeared - and found thousands of new victims. It claims to link to a video, with the comment: "During the summer holidays, this girl took the opportunity to do something unheard of! I bet no one can do the same".
Another message that's currently circulating widely pretends to link to a video of a giant snake eating a zookeeper.
In both cases, anyone clicking on the video finds that they must like or share it - spreading the scam far and wide. Users are then encouraged to complete an online survey - which is the real point of the exercise, as the scammers are paid a small amount for each one filled out. Needless to say, the videos are fake, or non-existent.
"Clearly if they manage to trick *many* Facebook users into sharing the link, and use a sensational video as bait, they're going to get a lot more people clicking on the link," warns security expert Graham Clueley.
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Other scam videos currently circulating include one titled '"Shark eats the swimming man in an Ocean!!' - which relies on an image from Jaws: The Revenge to tempt victims. Another claims to show a woman falling from a 220-foot roller-coaster, and a third the discovery of the world's largest snake.
Facebook itself warns users never to click on strange links, even if they come from friends. It has in the past taken so-called clickjackers to court, but has never managed to wipe the practice out. Indeed, last year, two Italian security researchers estimated the value of Facebook clickjacking at as much as $200 million per year.
Anyone falling for these scams is advised to report it to Facebook - and contact their friends to warn them not to click on the link themselves.