A fake 'dislike' button has been catching out Facebook users. The experts warn that if you fall for this scam, it will run code on your computer, and could leave you vulnerable to criminals.
So what do you need to watch for, and what are the most worrying Facebook scams?
The scamThe scam appears as a link on your wall saying 'Facebook now has a dislike button! Click 'Enable Dislike Button' to turn on the new feature.' If you click on the link it will immediately post itself to your profile - thereby spreading it to your friends. In addition it will run what the experts call 'obfuscated Java' on your computer.
It essentially means you are giving criminals permission to access your profile, post spam and get you to complete online surveys to give them yet more information about you.
Security experts. Sophos, say: "As we've explained before, there is no official dislike button provided by Facebook and there isn't ever likely to be. But it remains something that many Facebook users would like, and so scammers have often used the offer of a "Dislike button" as bait for the unwary."
Protect yourselfThis scam has run before, most memorably in August 2010. In both instances, the scammers use a genuine piece of software as bait. It was developed by Thomas Moquet, and is available through Firefox add ons. The scammers are merely using it to get users to download their rogue app.
If you have downloaded something you are worried about, it's worth deleting it from your account as soon as possible, revoking the right to access your data, and reporting it to Facebook.
It's also worth keeping your virus software up to date, so it can keep an eye on whether anything malicious has been downloaded from Facebook - or indeed anywhere else.
Top three scamsThis is one of the top three Facebook scams of 2012 so far. The others include:
Facebook Cashback scamThis was the big news of last week, where scammers were faking a cashback offer. They told users they could link their debit card to their Facebook account and earn 20% cashback whenever they spent any money.
They use this as bait to get users to accept their application - which immediately posts to their friends. They then take your debit card details for their own criminal purposes.
See who has been viewing your profileThese scams have come in a number of forms, but what they have in common is they offer a link to an app that supposedly lets you see who has been accessing your profile. If you click on it and let it access your account it messages your friends with the same scam.
It then has access to your account, and the ability to download malicious code onto your computer. The experts highlight that there is no way of telling who has been viewing your profile - so these sorts of apps are always a scam.