Researchers at Arbor Networks have come across a new piece of malware that could be linked to the Trojan used in the campaign known as Operation Potao Express.
The malware caught the attention of Arbor Networks researchers after a link to a VirusTotal analysis was posted on Twitter by an Italy-based expert who uses the online moniker Antelox. An analysis of the Trojan and its dropper showed that the threat could be linked to the Potao malware family.
The Potao malware, which has been described as a “universal modular cyber espionage toolkit,” has been around since at least 2011, but it was first analyzed in detail in 2015 by ESET.
In its report on Operation Potao Express, ESET said the malware was most probably of Russian origin and it had been used in attacks aimed at entities in Ukraine, Russia, Georgia and Belarus, including what experts described as “high-value targets.”
The new malware that Arbor Networks believes may be linked to Potao has been dubbed “Acronym” based on a debugging string and the URLs pointing to command and control (C&C) servers. Acronym and its dropper appear to have been compiled in mid-February.
The dropper is designed to kill the wmpnetwk.exe Windows process and replace the legitimate wmpnetwk.exe file with the malware.
Once executed, Acronym uses the Registry or the Task Scheduler to ensure that it’s persistent. It then contacts a C&C server and sends it information about the infected machine.
Similar to Potao, Acronym is a modular malware. Its built-in commands allow attackers to capture screenshots, download and execute other files, and run plugins. Since the C&C servers were offline at the time of Arbor’s analysis, researchers have not been able to identify any of the plugins.
However, similarities in the plugin functionality have led experts to believe that Acronym may be connected to Potao. Other similarities include the use of the same C&C infrastructure, attempts to contact C&C domains on the same ports, and the use of temporary file names that start with “HH.”
On the other hand, there are several differences when it comes to encryption and how the malware is delivered – unlike Potao, Acronym’s dropper does not use decoy documents, DLL files or process injections. Furthermore, some parts of the Acronym code, including for HTTP communications, encryption and the screenshot functionality, appear to have been copied from publicly available.