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Stealing Documents Through Social Media Image-Sharing

Innocent-looking vacation pictures on Facebook could conceivably traffic exfiltrated documents, Black Hat researchers warn

Security researchers will unveil at Black Hat USA a new method of hiding sensitive information in the encoding of seemingly safe images shared on social media sites to avoid security mechanisms. The method employed by a new tool they developed called SNScat can not only be used to exfiltrate data off networks without detection, but to also run covert botnets through the type of social media network traffic allowed by most businesses today.

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Developed by Dan Gunter and Solomon Sonya, post-graduate students at University of Louisville and Western International University, respectively, SNScat and its underlying operational methods take advantage of the opacity of traffic running through third-party social media sites, such as Facebook, Twitter, and YouTube.

"If you now get rid of the actual adversary's IP address, if you get rid of all his information from a network, and then you just have a third party or different medium that everyone is talking to, and then I am now taking to that same medium -- unless you have access to the third party, you can never determine where I'm actually sitting or where I'm coming from," Sonya says.

Couple that with steganography, and a whole world of attacks open up, Sonya says. At Black Hat he and Gunter will demonstrate how they were able to break up sensitive data files, scatter their bits and bytes in the coding of image files, transmit those images undetected through social media sites, and then reconstitute them outside of the test network.

"Any single file on your system is all composed of bits; it's all composed of bytes. If I can take away some bytes -- or just one bit -- randomly throughout an image file, the image is still going to be encoded the same," Sonya says, explaining that it might make the difference between one shade of blue or another if you took away a particular piece of encoding for color and replaced it with something else.

In the case of exfiltration, that something else could be any number of things, including the formula for whatever special sauce an organization produces.

"If I have that secret formula, I cannot just upload that formula into an email and send it out because I'm assuming that network security is in place that's looking for keywords in that formula file," Sonya says. "If now I take apart that entire file -- say it's the secret formula in a [100-byte] text file -- [and] fragment that text file into pieces five or six bytes each, it's all the same file, just now in 20 fragments. Now, if within each of the 20 fragments I convert all the bytes into bits and take those fragmented bits and scatter them into images and send those images up onto Twitter, all [an admin sees] is people uploading images."

But the attacker sees something very different. Once the attacker loads each of the 20 images, it is just a matter of composing all of the bits together to reconstitute the files.

"Now I've just created the original document extracted from a protected network without anyone ever knowing that I just sent a protect file off," he says.

The tool that Sonya and Gunter developed through their research not only can be used to exfiltrate data, but also to set up two-way communication between a network and a botnet command-and-control server through virtually undetectable social media traffic.

"They are in near real-time executing the commands that we give it and executing commands that we send to it easily -- just as you would have done with any other remote access tool or RAT -- but now you don't see anything different [on the network]," Sonya explains. "Using steganography, we're embedding our information into images [and] setting it onto the site. The implant downloads images, extracts the commands from it, executes the commands, and either does what you told it to or places messages back into images and back onto social networking sites."

Sonya says that by promoting SNScat, he and Gunter hope to give security researchers and white hats the tools needed to look into these types of social networking vulnerabilities, which has wide-ranging applicability not only through use of images, but also audio and video files.

"If we stop looking at files as 'this file is an image, this is a text file, this is a video,' we'll see that all files are bytes," he says. "That means the same algorithm we use to embed information and extract what's on any file applies not just to images."

While he did have reservations in offering a tool that could potentially be used as a new undetectable method of exfiltration in the wild, Sonya says he and his research partner believed that the release of SNScat was necessary to get the industry prepared for these type of potential attacks from malicious adversaries.

"We're working together on this project in our free time -- and we both work and go to school full-time," he says. "So now imagine the motivated attacker who is paid to do this eight or 10 hours a day. We can only imagine the already advanced tools that they've already developed. We're just bringing this attack method to light."

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