Facebook has been hit by another clickjacking worm attack.

In the new attack, the worm updates a user's Facebook profile to indicate that they like a page called "101 Hottest Women in the World." Clicking on the link leads to a picture of actress Jessica Alba containing a clickjacking link. Other variations on the attack seen this week have offered a "free Farmville secrets e-book," a complimentary online viewing of Sex and the City 2 or the Ultimate Fight Club, as well as promises of naked celebrities.

Also known as likejacking, clickjacking attacks exploit the "like" button functionality that Facebook developed for third-party sites. The attack tricks a user into clicking the "like" button -- oftentimes by overlaying it with a fake link -- which generates a status update on the user's Facebook page, including a link to the attack.

"Presumably, somebody's making money from all this," said Richard Cohen of SophosLabs on the company's blog. "Though we still haven't seen this technique being used as an attack vector to infect users, it's still an underhanded and malicious technique, and it's driving swarms of people to pages serving up adverts."

In the wake of these new attacks, security experts renewed their call for Facebook to take a tougher approach to site security. "It's clear that Facebook needs to set up a proper early-warning system to alert users about breaking threats," said Graham Cluley, a senior technology consultant at Sophos, on the company's blog. "It seems wrong that the only place where Facebook users can read about the latest attacks is on the pages run by security vendors on Facebook, rather than Facebook's own security pages."

He also recommended that Facebook add some kind of interstitial message or pop-up to verify that users really do want to "like" something, as well as an opt-out capability. Currently, simply pressing the "like" button, even on a third-party Web site, immediately activates the feature.

"Although the attacks are yet to deliver malicious payloads, they demonstrate an exploitable weakness in the way that Facebook works, putting users at potential risk from future malware or phishing attacks," said Cluley.

Facebook users agree, according to a straw poll conducted overnight by Sophos on its Web site. Of the 600 people who responded, 95% said that Facebook wasn't doing enough to stop clickjacking worms.

Black Hat USA 2010 presents a unique opportunity for members of the security industry to gather and discuss the latest in cutting-edge research. It happens July 24-29, in Las Vegas. Find out more and register.