A major computer security firm urged Facebook on Tuesday to set up an early-warning system after hundreds of thousands of users were hit by a new wave of fake sex-video attacks.
British-based virus fighter Sophos warned users of the world's biggest social networking site to be on guard against any posting entitled "distracting beach babes", which contains a movie thumbnail of a bikini-clad woman.
In a press statement, Sophos said the malicious posts appear as if they are coming from Facebook users' friends, but it urged recipients not to click on the thumbnail.
By clicking on it, users are taken to a rogue Facebook application informing them that they do not have the right player software installed, Sophos said.
It tricks users into installing adware, a software package that automatically plays, displays or downloads advertisements to their computer, and the video link is spread further across the network.
Sophos said that "hundreds of thousands" of Facebook users were believed to have received the posts over the past weekend.
It followed a similar scam that spread on Facebook the week before involving a fake posting tagged as the "sexiest video ever".
"It's time for Facebook to set up an early warning system on their network, through which they can warn their almost 500 million users about breaking threats as they happen," said Graham Cluley, senior technology consultant at Sophos.
"A simple message appearing on all users' screens warning them of the outbreak would have helped in halting the attack," he said.
"Unless something is done, it won't be surprising if there is another widespread attack this coming weekend, affecting thousands more users."
The social networking site is already under fire for revealing users' information too freely on the Internet.
Facebook chief executive Mark Zuckerberg said Monday that the website "missed the mark" with its complex privacy controls and would reveal simpler features in the coming weeks.