Facebook Virus warning
Facebook's 120 million users are being targeted by a virus designed to get hold of sensitive information like credit card details.
'Koobface' spreads by sending a message to people's inboxes, pretending to be from a Facebook friend.
It says "you look funny in this new video" or "you look just awesome in this new video".
By clicking on the link provided they're then asked to watch a "secret video by Tom".
When users try and play the video they're asked to download the latest version of Adobe Flash Player.
If they do, that's when the virus takes hold and attacks the computer.
Guy Bunker works for Norton AntiVirus and says there are two ways Koobface gets people's credit card details.
"It can either wait for you to buy something online and just remember the details you type in on your keyboard.
"Otherwise it can search your computer for any cookies you might have from when you've bought something in the past, and take them from there."
MySpace was targeted by Koobface in August this year.