A piece of malware used in attacks by the Russia-linked cyberespionage group known as Turla is designed to obtain the address of its command and control (C&C) servers from comments posted to Instagram.
Turla is believed to have been active since at least 2007, but there is also some evidence linking the threat actor to one of the earliest cyberespionage operations. The group is also known as Waterbug, KRYPTON and Venomous Bear, and some of its primary tools are tracked as Turla (Snake and Uroburos) and Epic Turla (Wipbot and Tavdig).
The group is still active and it has been spotted developing new malware and improving its existing tools. The cyberspies have recently targeted the websites of ministries, embassies and other organizations from around the world in a reconnaissance campaign.
The security firm ESET has been monitoring this campaign and noticed that the hackers have once again started abusing social media.
The campaign has involved watering hole attacks, where the group planted malicious code on compromised websites in an effort to redirect their visitors to a server that delivered a JavaScript tool designed for profiling victims.
In one of the watering hole attacks, ESET came across a Firefox extension that acted as a backdoor. The extension appears to be an update to a similar tool previously analyzed by Bitdefender in its Pacifier APT report.
The malicious Firefox extension analyzed by ESET had been distributed through the website of a Swiss security company’s website. The malware is designed to collect information on the infected system, and it allows attackers to perform various tasks, including executing files, uploading and downloading files, and reading the content of a directory.
What makes this backdoor interesting is the way it obtains the address of its C&C server. The sample discovered by ESET generated a URL by looking for a specific comment posted to a photo on Britney Spears’ Instagram account.
The comment in question read “#2hot make loved to her, uupss #Hot #X,” which might not seem like something written by cyberspies. However, running a regular expression on the comment reveals a bit.ly URL that represents the backdoor’s C&C server.
The malicious extension knows which comment contains the C&C address by computing a custom hash value that must match 183. The bit.ly URL generated for the sample analyzed by ESET was only accessed 17 times, which could indicate that it was only part of a test.
On the other hand, researchers pointed out that some of the APIs used by the extension will no longer work in future Firefox releases, which means upcoming versions of the backdoor will have to be implemented differently.
Turla is not the only APT actor caught using social media for C&C communications. The group known as the Dukes were spotted leveraging Twitter a few years ago.
