ESET researchers have observed a significant change in the campaign of the infamous espionage group

Turla is a notorious espionage group, and has been active for at least ten years. It came to light in 2008, when Turla breached the US Department of Defense [1]. Since then, there have been numerous security incidents involving Turla targeting several governments and sensitive businesses such as the defense industry [2].

Our January 2018 white paper [3] was the first analysis of a Turla campaign called Mosquito. We have also published indicators of compromise [4]. Since then, the campaign has remained very active and attackers have been busy changing their tactics to remain as stealthy as possible.

Starting in March 2018, we observed a significant change in the campaign: it now leverages the open source exploitation framework Metasploit before dropping the custom Mosquito backdoor. It is not the first time Turla has used generic tools. In the past, we have seen the group using open-source password dumpers such as Mimikatz. However, to our knowledge, this is the first time Turla has used Metasploit as a first stage backdoor, instead of relying on one of its own tools such as Skipper [5].

Distribution

As described in our earlier analysis [3], the typical vector of compromise of the Mosquito campaign is still a fake Flash installer, in reality installing both the Turla backdoor and the legitimate Adobe Flash Player. The typical targets are still embassies and consulates in Eastern Europe.

We showed that the compromise happens when the user downloads a Flash installer from get.adobe.com through HTTP. Traffic was intercepted on a node between the end machine and the Adobe servers, allowing Turla’s operators to replace the legitimate Flash executable with a trojanized version. The following image shows the different points where the traffic could in theory be intercepted. Please that we believe the fifth possibility to be excluded, as, to the best of our knowledge, Adobe/Akamai was not compromised.

- figure1 - Mosquito campaign by Turla undergoes significant TTPs shift

Even though we were not able to spot traffic interception subsequently, we found a new executable that is still impersonating the Flash installer and is named flashplayer28_xa_install.exe. Thus, we believe the same method of initial compromise is still being used.

Analysis

At the beginning of March 2018, as part of our regular tracking of Turla’s activities, we observed some changes in the Mosquito campaign. Even though they did not make use of groundbreaking techniques, this is a significant in Turla’s Tactics, Techniques and Procedures ().

Previously, the chain of compromise was a fake Flash installer dropping a loader and the main backdoor. The following figure summarizes the process.

- figure2 - Mosquito campaign by Turla undergoes significant TTPs shift

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. 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. The figure below summarizes the new process.

- figure3 - Mosquito campaign by Turla undergoes significant TTPs shift

Because Metasploit is being used, we might also guess that an operator controls the exploitation process manually. The time frame of the attack was relatively short as the final backdoor was dropped within thirty minutes of the start of the compromise attempt.

The shellcode is a typical Metasploit shellcode, protected using the shikata_ga_nai encoder [7] with seven iterations. The following screenshots show the encoded and the decoded payload.

- figure4 - Mosquito campaign by Turla undergoes significant TTPs shift

- figure5 - Mosquito campaign by Turla undergoes significant TTPs shift

Once the shellcode is decoded, it contacts its C&C at https://209.239.115[.]91/6OHEJ, which directs the of an additional shellcode. 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.

Additional tools

In addition to the new fake Flash installer and Meterpreter, we observed the use of several other tools.

  • 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>AppDataRoamingMicrosoftWindowsStart MenuProgramsStartupmsupdateconf.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].

Conclusion

In this post, we have presented the evolutions of the Turla Mosquito campaign over the last few months. The major change we observed was the use of Metasploit, an open-source penetration testing project, as a first stage for the custom Mosquito backdoor. This might be useful information for defenders performing incident response on involving Turla.
For any inquiries, or to make sample submissions related to the subject, contact us at [email protected]

C&C

  • https://209.239.115[.]91/6OHEJ
  • https://70.32.39[.]219/n2DE3

Link to the legitimate Flash installer

  • https://drive.google[.]com/uc?authuser=0&id=1s4kyrwa7gCH8I5Z1EU1IZ_JaR48A7UeP&export=download

IoCs

Filename SHA1 SHA256 ESET detection name
flashplayer28_xa_install.exe 33d3b0ec31bfc16dcb1b1ff82550aa17fa4c07c5 f9b83eff6d705c214993be9575f8990aa8150128a815e849c6faee90df14a0ea Win32/TrojanDownloader.Agent.DWY trojan
msupdateconf.exe 114c1585f1ca2878a187f1ce7079154cc60db7f5 11933d6526416e07a5f20022cd3c5c79b73e8a33e80f29f9b06cdc3cb12e26 Win32/Turla.DH trojan
msupdatesmal.exe 994c8920180d0395c4b4eb6e7737961be6108f64 6868cdac0f06232608178b101ca3a8afda7f31538a165a045b439edf9dadf048 Win32/Turla.DH trojan

References

[1] B. KNOWLTON, “Military Computer Attack Confirmed,” New York Times, 25 08 2010. [Online]. Available: https://www.nytimes.com/2010/08/26/technology/26cyber.html?_r=1&ref=technology. [Accessed 09 04 2018].

[2] MELANI, ” Technical Report about the Malware used in the Cyberespionage against RUAG,” 23 05 2016. [Online]. Available: https://www.melani.admin.ch/melani/en/home/dokumentation/reports/technical-reports/technical-report_apt_case_ruag.html.

[3] ESET, “Diplomats in Eastern Europe bitten by a Turla mosquito,” ESET, 01 2018. [Online]. Available: https://www.welivesecurity.com/wp-content/uploads/2018/01/ESET_Turla_Mosquito.pdf.

[4] ESET, “Mosquito Indicators of Compromise,” ESET, 09 01 2018. [Online]. Available: https://github.com/eset/malware-ioc/tree/master/turla#mosquito-indicators-of-compromise.

[5] M. Tivadar, C. Istrate, I. Muntean and A. Ardelean, “Pacifier APT,” 01 07 2016. [Online]. Available: https://labs.bitdefender.com/wp-content/uploads/downloads/pacifier-apt/.

[6] “About the Metasploit Meterpreter,” [Online]. Available: https://www.offensive-security.com/metasploit-unleashed/about-meterpreter/.

[7] “Unpacking shikata-ga-nai by scripting radare2,” 08 12 2015. [Online]. Available: http://radare.today/posts/unpacking-shikata-ga-nai-by-scripting-radare2/.

[8] “meterpreter/source/extensions/priv/server/elevate/,” Rapid7, 26 11 2013. [Online]. Available: https://github.com/rapid7/meterpreter/tree/master/source/extensions/priv/server/elevate.






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