Security experts have warned of a new scam which appears to be threatening Facebook users.
Graham Cluley, senior technology consultant at Sophos, explained that users of the social networking site are reacting to a mystery application that may or may not be spying on them.
Facebook users are passing around a message, warning each other about the application, called the 'Unnamed app', and unwittingly creating an opportunity for hackers.
"Users are told in the warning that they can find the 'Unnamed app' by going to 'Settings'/'Application Settings' and then choosing 'Add to Profile' from the drop-down box," said Cluley in a blog post.
"Sure enough, when I went to look on a Facebook account, I found an 'Unnamed app'."
Whether the application is malicious or not remains a mystery, according to Cluley. "It seems to me that the only sin it may have committed might be to have been given a daft unhelpful name," he said.
"According to Facebook itself, it appears to be a buggy presentation of the boxes tab that appears on users' Facebook profiles."
However, hackers have exploited the warning messages and created web pages that relate to the 'unnamed' application. Cluley said that, by using search engine optimisation tools, the hackers have taken their pages to the top of search results.
"If you happen to stumble across one of these malicious sites after searching for information about the 'Facebook Unnamed app' you might find yourself infected by fake anti-virus software designed to trick you out of your hard-earned cash," said Cluley.
Sophos has identified the malware on these infected web pages as Mal/FakeVirPk-A.