The scam culminates with a list of surveys, similar to those used in a 'Dislike' button clickware scam discovered earlier this week and a Like button scam uncovered in June, according to anti-virus developer Sophos, which uncovered the con.
Those behind this latest Share button scam want Facebook users to answer a few questions within a simple survey; one blank is the request for a cell phone number. By providing their cell phone number without reading the fine print, users are subscribing to a paid-phone, automatically renewing service that charges $5 per week via the cell phone bill.
"Unfortunately, most people won't read the fine print and will willingly hand over the information and likely won't notice the charges until the end of the month," said Onur Komili, researcher at SophosLabs, Canada, in a company blog.
Facebook has removed fan pages associated with the scam, he said.
In this latest scam, Facebook account-holders see a fan page and are offered the chance to see the "Top 10 Funny T-Shirt Fails ROFL," according to anti-virus developer Sophos, which came across the clickjacking scheme today. Once unwitting Facebook users load the page, the tab grasps the malicious script from an external domain that forces users to automatically share the page on their profile, said Komili.
Those using Firefox plug-in NoScript receive a warning, cautioning them that NoScript "intercepted a mouse or keyboard interaction with a partially hidden element." At this point, users have the option to keep the element locked, which is recommended, or disregarding NoScript's recommendation and opening up the link.
However, those Facebook account-holders not running NoScript or not paying attention will find their profile pages sharing content that links them to a malicious domain, said Komili.
"Clicking the link sends you to one of many fan pages all serving the exact same content. It seems a fan page is chosen at random," he said.
Anyone victimized by this scam should select "Remove" to clear the content from their profile and help prevent the further spreading of the social networking disease, said Komili.
Sophos was in the process of publishing detection of this so-called Sharejacking threat as a Troj/FBJack-A and its software is blocking the domain that hosts the malicious code, he said.