MQsTTang: Mustang Panda’s newest backdoor treads new floor with Qt and MQTT

ESET researchers have analyzed MQsTTang, a brand new customized backdoor that we attribute to the Mustang Panda APT group. This backdoor is a part of an ongoing marketing campaign that we are able to hint again to early January 2023. In contrast to a lot of the group’s malware, MQsTTang doesn’t appear to be primarily based on current households or publicly out there tasks.

Mustang Panda is understood for its custom-made Korplug variants (additionally dubbed PlugX) and elaborate loading chains. In a departure from the group’s regular ways, MQsTTang has solely a single stage and doesn’t use any obfuscation methods.

Victimology

We’ve seen unknown entities in Bulgaria and Australia in our telemetry. We even have data indicating that this marketing campaign is concentrating on a governmental establishment in Taiwan. Nevertheless, as a result of nature of the decoy filenames used, we consider that political and governmental organizations in Europe and Asia are additionally being focused. This might even be according to the concentrating on of the group’s different current campaigns. As documented by fellow researchers at Proofpoint, Mustang Panda has been identified to focus on European governmental entities since at the least 2020 and has elevated its exercise in Europe even additional, since Russia’s invasion of Ukraine. Determine 1 reveals our view of the concentrating on for this marketing campaign.

Determine 1. Map exhibiting identified and suspected targets of MQsTTang

Attribution

We attribute this new backdoor and the marketing campaign to Mustang Panda with excessive confidence primarily based on the next indicators.

We discovered archives containing samples of MQsTTang in two GitHub repositories belonging to the consumer YanNaingOo0072022. One other GitHub repository of the identical consumer was utilized in a earlier Mustang Panda marketing campaign described by Avast in a December 2022 blogpost.

One of many servers used within the present marketing campaign was operating a publicly accessible nameless FTP server that appears to be used to stage instruments and payloads. Within the /pub/god listing of this server there are a number of Korplug loaders, archives, and instruments that had been utilized in earlier Mustang Panda campaigns. This is similar listing that was utilized by the stager described within the aforementioned Avast blogpost. This server additionally had a /pub/gd listing, which was one other path utilized in that marketing campaign.

A few of the infrastructure used on this marketing campaign additionally matches the community fingerprint of beforehand identified Mustang Panda servers.

Technical evaluation

MQsTTang is a barebones backdoor that permits the attacker to execute arbitrary instructions on a sufferer’s machine and get the output. Even so, it does current some attention-grabbing traits. Chief amongst these is its use of the MQTT protocol for C&C communication. MQTT is usually used for communication between IoT units and controllers, and the protocol hasn’t been utilized in many publicly documented malware households. One such instance is Chrysaor, also referred to as Pegasus for Android. From an attacker’s perspective, one among MQTT’s advantages is that it hides the remainder of their infrastructure behind a dealer. Thus, the compromised machine by no means communicates immediately with the C&C server. As seen in Determine 2, this functionality is achieved through the use of the open supply QMQTT library. This library is dependent upon the Qt framework, a big a part of which is statically linked within the malware. Utilizing the Qt framework for malware growth can also be pretty unusual. Lazarus’s MagicRAT is likely one of the uncommon lately documented examples.

Determine 2. RTTI exhibiting lessons from the QMQTT library

MQsTTang is distributed in RAR archives which solely include a single executable. These executables often have names associated to Diplomacy and passports similar to:

• CVs Amb Officer PASSPORT Ministry Of Overseas Affairs.exe
• Paperwork members of delegation diplomatic from Germany.Exe
• PDF_Passport and CVs of diplomatic members from Tokyo of JAPAN.eXE
• Notice No.18-NG-23 from Embassy of Japan.exe

These archives are hosted on an internet server with no related area identify. This reality, together with the filenames, leads us to consider that the malware is unfold through spearphishing.

To this point, we have now solely noticed a number of samples. Apart from variations in some constants and hardcoded strings, the samples are remarkably related. The one notable change is the addition of some anti-analysis methods within the newest variations. The primary of those consists of utilizing the CreateToolhelp32Snapshot Home windows API perform to iterate by operating processes and search for the next identified debuggers and monitoring instruments.

• cheatengine-x86_64.exe
• ollydbg.exe
• ida.exe
• ida64.exe
• radare2.exe
• x64dbg.exe
• procmon.exe
• procmon64.exe
• procexp.exe
• processhacker.exe
• pestudio.exe
• systracerx32.exe
• fiddler.exe
• tcpview.exe

Notice that, whereas the malware is a 32-bit executable, it solely checks for the presence of x64dbg and never its 32-bit counterpart, x32dbg.

The second method makes use of the FindWindowW Home windows API to search for the next Window Courses and Titles utilized by identified evaluation instruments:

• PROCMON_WINDOW_CLASS
• OLLYDBG
• WinDbgFrameClass
• OllyDbg – [CPU]
• Immunity Debugger – [CPU]

When executed immediately, the malware will launch a replica of itself with 1 as a command line argument. That is repeated by the brand new course of, with the argument being incremented by 1 on each run. When this argument hits particular values, sure duties will probably be executed. Notice that the precise values fluctuate between samples; those talked about under correspond to the pattern with SHA-1 02D95E0C369B08248BFFAAC8607BBA119D83B95B. Nevertheless, the duties themselves and the order through which they’re executed is fixed.

Determine 3 reveals an outline of this habits together with the duties which can be executed when the malware is first run.

Determine 3. Execution graph exhibiting the subprocesses and executed duties

Desk 1 incorporates an inventory of the duties and the worth at which every of them is executed. We are going to describe them in additional element within the upcoming paragraphs.

Desk 1. Duties executed by the backdoor

If any evaluation software or debugger is detected utilizing the methods we described beforehand, the habits of process 1 is altered and duties 2, 3, and 4 are skipped completely.

Job 1: C&C communication

As was beforehand talked about, MQsTTang communicates with its C&C server over the MQTT protocol. All noticed samples use 3.228.54.173 as dealer. This server is a public dealer operated by EMQX, who additionally occur to be the maintainers of the QMQTT library. This may very well be a option to make the community site visitors appear reputable and to cover Mustang Panda’s personal infrastructure. Utilizing this public dealer additionally supplies resiliency; the service is unlikely to be taken down due to its many reputable customers and, even when the present C&C servers are banned or taken down, Mustang Panda might spin up new ones and use the identical MQTT matters with out disrupting MQsTTang’s operation.

Nevertheless, this marketing campaign may be a check case by Mustang Panda earlier than deciding whether or not to take a position the time and assets to arrange their very own dealer. That is supported by the low variety of samples we’ve noticed and the quite simple nature of MQsTTang.

As proven in Determine 4, the malware and C&C server use two MQTT matters for his or her communication. The primary one, iot/server2, is used for communication from the shopper to the server. The second is used for communication from the server to the shopper. It follows the format iot/v2/<Distinctive ID> the place <Distinctive ID> is generated by taking the final 8 bytes, in hex kind, of a UUID. If any evaluation software is detected, server2 and v2 are respectively changed with server0 and v0. That is possible with the intention to keep away from tipping off defenders by completely aborting the malware’s execution early.

Determine 4. Simplified community graph of the communication between the backdoor and C&C server

All communication between the server and the shopper makes use of the identical encoding scheme. The MQTT message’s payload is a JSON object with a single attribute named msg. To generate the worth of this attribute, the precise content material is first base64 encoded, then XORed with the hardcoded string nasa, and base64 encoded once more. We are going to describe the precise format of those payloads within the related sections.

Upon first connecting to the dealer, the malware subscribes to its distinctive subject. Then, and each 30 seconds thereafter, the shopper publishes a KeepAlive message to the server’s subject. The content material of this message is a JSON object with the next format:

When the server desires to difficulty a command, it publishes a message to the shopper’s distinctive subject. The plaintext content material of this message is just the command to be executed. As proven in Determine 5, the shopper executes the obtained command utilizing QProcess::startCommand from the Qt framework. The output, obtained utilizing QProcess::readAllStandardOutput, is then despatched again in a JSON object with the next format:

Determine 5. Execution of obtained instructions utilizing the QProcess class

Since solely the content material of ordinary output is shipped again, the server won’t obtain errors or warnings. From the server’s standpoint, a failed command is thus indistinguishable from a command that merely produces no output except some type of redirection is carried out.

Duties 2 and three: Copying the malware

The second and third duties are pretty related to one another. They copy the malware’s executable to a hardcoded path; c:userspublicvdump.exe and c:userspublicvcall.exe respectively. The filenames used are totally different for every pattern, however they’re all the time positioned within the C:userspublic listing.

Within the second process, the newly created copy is then launched with the command line argument 97.

Job 4: Establishing persistence

Persistence is established by the fourth process, which creates a brand new worth qvlc set to c:userspublicvcall.exe below the HKCUSoftwareMicrosoftWindowsCurrentVersionRun registry key. This may trigger the malware to be executed on startup.

When MQsTTang is executed on startup as c:userspublicvcall.exe, solely the C&C communication process is executed.

Conclusion

The Mustang Panda marketing campaign described on this article is ongoing as of this writing. The victimology is unclear, however the decoy filenames are according to the group’s different campaigns that concentrate on European political entities.

This new MQsTTang backdoor supplies a type of distant shell with none of the bells and whistles related to the group’s different malware households. Nevertheless, it reveals that Mustang Panda is exploring new know-how stacks for its instruments. It stays to be seen whether or not this backdoor will grow to be a recurring a part of the group’s arsenal, however it’s yet one more instance of the group’s quick growth and deployment cycle.

IoCs

Information

Community

Github repositories

• https://uncooked.githubusercontent[.]com/YanNaingOo0072022/14/essential/Paperwork.rar
• https://uncooked.githubusercontent[.]com/YanNaingOo0072022/ee/essential/CVs Amb.rar

MITRE ATT&CK methods

This desk was constructed utilizing version 12 of the MITRE ATT&CK framework.