Turla is the name of a Russian cyber espionage APT group (also known as Waterbug, Venomous Bear and KRYPTON) that has been active since at least 2007 targeting government organizations and private businesses.

The list of victims is long and includes also the Swiss defense firm RUAG, US Department of State, and the US Central Command.

The Turla’s arsenal is composed of sophisticated hacking tools and malware tracked as Turla (Snake and Uroburos rootkit), Epic Turla (Wipbot and Tavdig) and Gloog Turla. In June 2016, researchers from Kaspersky reported that the Turla APT had started using rootkit), Epic Turla (Wipbot and Tavdig) and Gloog Turla.

In the most recent attacks, the group is packaging its macOS backdoor with a real Adobe Flash installer and downloading the malware on victim systems from endpoint systems that use a remote IP belonging to Akamai, the Content Delivery Network that is also used by Adobe for its supply chain. Legitimate Flash installer, in fact, are also distributed through the Akamai network.

Mosquito campaign still leverages fake Flash installer that hides the Turla backdoor.

When victims download the Flash installer from get.adobe.com through HTTP attackers intercept the traffic to serve a tainted version of the legitimate Flash executable.

“At the beginning of March 2018, as part of our regular tracking of Turla’s activities, we observed some changes in the Mosquito campaign.”

“Recently, we observed a change in the way in which the final backdoor is dropped. Turla’s campaign still relies on a fake Flash installer but, instead of directly dropping the two malicious DLLs, it executes a Metasploit shellcode and drops, or downloads from Google Drive, a legitimate Flash installer.” reads the report published by ESET. “Then, the shellcode downloads a Meterpreter, which is a typical Metasploit payload [6], allowing the attacker to control the compromised machine. Finally, the machine may receive the typical Mosquito backdoor.”

Attackers control the exploitation process manually through the use of the Metasploit framework, the overall time frame of the attack was relatively short. According to ESET, the attackers are able to deliver the final backdoor in just thirty minutes.

“The shellcode is a typical Metasploit shellcode, protected using the shikata_ga_nai encoder [7] with seven iterations. Once the shellcode is decoded, it contacts its C&C at https://209.239.115[.]91/6OHEJ, which directs the download of an additional shellcode.” continues the report.

“Based on our telemetry, we identified the next stage to be a Meterpreter. That IP address is already known as a previously seen Mosquito C&C domain, psychology-blog.ezua[.]com, was resolving to it in October 2017. Finally, the fake Flash installer downloads a legitimate Adobe installer, from a Google Drive URL, and executes it to lull the user into thinking all went correctly.”

Experts noticed that in addition to the new fake Flash installer and Meterpreter, the hackers used many other tools, including:

• A custom executable that only contains the Metasploit shellcode. This is used to maintain access to a Meterpreter session. It is saved to C:\Users\<username>\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup\msupdateconf.exe, granting the executable persistence.
• Another custom executable used to execute PowerShell scripts.
• The Mosquito JScript backdoor that uses Google Apps Script as its C&C server.
• Privilege escalation using the Metasploit module ext_server_priv.x86.dll [8].

Further details, including IoC are included in the report.

Pierluigi Paganini

(Security Affairs – Turla APT group, cyber espionage)

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