A weekend of Click-jacking on Facebook
Posted by Stephan Chenette on 02 May 2011 11:47 PM
In this blog post, I will analyze a Facebook scam technique that we've seen grow in popularity over the past few weeks, but let's focus on one example that was circulating this past weekend. As a Websense customer, if you are running our Web Security Software or real-time analytics, your users would have been protected from the first link right off the bat, thanks to our Advanced Classification Engine (ACE):
To show how this particular attack works, I set up a scenario using a test account. In this scenario, a friend named Chris has already fallen for the scam and posted a comment to his own Facebook profile page, which appears on all of his friends' walls.
Here's what Chris, a victim of this scam, commented on:
Remember scammers aren't going to post something boring, this is meant to be enticing ... OK, I'll play along. Let's see what happens as I follow the trail. By clicking on the link, I'm redirected to mcdshock DOT info (robtex):
A Real CAPTCHA?
Interesting. So this site says that I can only continue if I solve a CAPTCHA. The site explains that it's using the CAPTCHA because it is attempting to protect itself from BOTS. That seems to make sense. CAPTCHAs are in fact meant to tell humans and programs apart (in theory) - but this particular page has more going on than meets the eye.
Let's look at the source code behind this page (full source code can be found here):
The first thing that is noticeably odd is that the source code indicates the use of the Facebook comments social plugin (see fb:comments code) that allows websites to include a comment box linking to a user's Facebook page if they are logged into Facebook in another window or tab. A typical comment box looks like this:
But looking at the source code, no such comment box was displayed. Let's take an even closer look at the source code to figure out why ...
The style sheet section of the source code shows that the Facebook comment box is being wrapped in a div that has been given a style making it completely invisible (see opacity):
Next the source code is overlaying a background image on the entire section where the Facebook comment box is:
Can you guess what that image looks like? Here it is ...
Analysis of the source code indicates that the CAPTCHA is not a real CAPTCHA but an image sitting on top of a Facebook comment box meant to trick me, the unprotected user, into clicking on something - all the while, hiding its true nature. The submit button is carefully placed on top of the comment button. By clicking on it, I would be submitting text to my Facebook wall with text that is supplied by the scammer's website.
... and sure enough, once I hit submit, here is the comment that is posted to my Facebook page:
Classic case of click-jacking!
That's not the end of it though! What happens next after clicking submit, apart from a comment being posted to my profile page is that I'm redirected, first to a tracking website:
... and next to isozbanks DOT com, where I'm asked for further verification to either play a Pacman game or answer what my favorite Facebook game is:
Another click? Can you say clicking-jacking part deux? Indeed, if I click on one of the above links, another comment is posted to my Facebook profile page:
Click-jack complete, commence project information gathering
Next, I'll be redirected to playsushi DOT com (Alexa Ranking: 7903) where if I click on "Click Here To Play," I'll be prompted to download an executable called SetupPlaySushi.exe (VirusTotal report):
Had I chosen instead to take the survey of my favorite Facebook game, I would've been brought to the following pages where the attacker would have a very good opportunity to capture my email address and post another comment to my Facebook page. Upon clicking continue, I'd be asked to give out more information (a great method for attackers to build up a profile for tracking purposes and to store their victims' personal information).
Now assuming I either visited the Pacman site or the survey site, the following page is shown:
I then must proceed through a few more Web pages, which in the end ask me to play more games or fill out more surveys for verification purposes (it's worth noting that each user will be prompted with different games and different links) - again really just to trick me into clicking and sending comment spam to my own Facebook profile page:
Clicking one of these links will bring me to the following pages:
Finally after viewing any of the above sites, I'll get a final Web page screen indicating that the content has been unlocked and that I can view the video.
Is there even a real video to view?
At the end of this entire process, I'll be rewarded for my persistence by being able to finally see the video I was promised.
Let's review all that I had to give up to get to view the final video:
The Click-jacking to post comments to my profile was the main motivation from the attacker's point of view. Everything that came after was just a bonus.
To give you an estimate of how many people fell for this scam, we can look at the hits on YouTube yesterday and this morning, Overnight more than 100,000 users visited the YouTube video, showing how successful this scam really was.
Don't become a victim! Here are some tips and tools to protect yourself against Click-jacking (link). Websense has a free Facebook plugin called Websense TRITON Defensio that would have protected users from this attack. Install it, and it will protect you from these types of scams.
Web Filtering and real-time analytics within ACE would have protected a user from the start!
Principal Security Researcher: Stephan Chenette
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