Pierluigi Paganini November 29, 2014

Security experts have detected an attack against a major firm that used a data exfiltration technique based on the video steganography.

Threats actors in the wild are exfiltrating data with a technique based on video uploaded to cloud services. Attackers adopted this trick to move data from a compromised target outside without detection by conventional solutions, such as intrusion detection/prevention systems. To further improve the tactic, bad actors utilize steganography to hide encrypted data into video uploaded to an unmonitored video sharing service.

Why only videos and not images?

Security experts know that there are several tools available that can detect the use of steganography in images, these software are able in fact to detect signatures of common steganography tools and techniques. The situation is quite different for video and threat actors  using the exfiltration technique that we have described know it.

The attackers can use one several off the shelf tools or open source software (i.e. OpenPuff) to implement steganography of exfiltrated data. As revealed by TripWire in a blog post, one of the Fortune 500 companies was recently hit by hackers that used the above technique to exflitrate data.

The data exfiltration went undetected until the company noticed several duplicate video files had been uploaded from their network to a video sharing website.

There are a number of tools available that can detect the presence of steganography in images on a network, such as software to appliances designed specifically for detecting signatures of common steganography tools and techniques. The problem is they are generally designed to detect the use of steganography in images, not video. The groups using this as an exfiltration technique are well aware of this, hence why they are using video instead of images which would be an easier transport mechanism.

As mitigation strategy it is suggested to network administrators to monitor the installation of application or custom binaries used by attackers to encode data into a video or an image. Administrators should already be monitoring assets for new binaries on hosts. The administrators anyway need to monitor outcoming connections to external services that could

Another mitigation strategy to detect software that could be used in the data exfiltration technique described is to scan of host systems for video files especially for the assets that are critical in the network.

Also, by monitoring connections of a host system to external services administrators is possible to detect suspicious activity.

As explained by TripWire, in the case of the Fortune 500 company that was targeted with this data exfiltration technique, the attackers used the same videos to send different pieces out of the targeted network.

Pierluigi Paganini

(Security Affairs –  Data exfiltration, cybercrime)