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 will hint again to early January 2023. In contrast to a lot of the group’s malware, MQsTTang doesn’t appear to be based mostly on current households or publicly accessible 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 typical techniques, MQsTTang has solely a single stage and doesn’t use any obfuscation methods.

Victimology

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

Determine 1. Map displaying identified and suspected targets of MQsTTang

Attribution

We attribute this new backdoor and the marketing campaign to Mustang Panda with excessive confidence based mostly 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 working 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.

Among 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 enables 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 often 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 called Pegasus for Android. From an attacker’s perspective, one in every of MQTT’s advantages is that it hides the remainder of their infrastructure behind a dealer. Thus, the compromised machine by no means communicates straight with the C&C server. As seen in Determine 2, this functionality is achieved by utilizing the open supply QMQTT library. This library is determined by the Qt framework, a big a part of which is statically linked within the malware. Utilizing the Qt framework for malware improvement can also be pretty unusual. Lazarus’s MagicRAT is likely one of the uncommon not too long ago documented examples.

Determine 2. RTTI displaying courses 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 comparable 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
• Word No.18-NG-23 from Embassy of Japan.exe

These archives are hosted on an internet server with no related area title. This reality, together with the filenames, leads us to imagine that the malware is unfold by way of spearphishing.

To this point, we’ve got solely noticed just a few samples. Moreover variations in some constants and hardcoded strings, the samples are remarkably comparable. 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 operate to iterate by working 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

Word 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 approach makes use of the FindWindowW Home windows API to search for the next Window Lessons and Titles utilized by identified evaluation instruments:

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

When executed straight, the malware will launch a duplicate 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 might be executed. Word 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 summary of this conduct together with the duties which are executed when the malware is first run.

Determine 3. Execution graph displaying the subprocesses and executed duties

Desk 1 accommodates a listing of the duties and the worth at which every of them is executed. We’ll describe them in additional element within the upcoming paragraphs.

Desk 1. Duties executed by the backdoor

If any evaluation instrument or debugger is detected utilizing the methods we described beforehand, the conduct of job 1 is altered and duties 2, 3, and 4 are skipped solely.

Process 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 might be a technique to make the community visitors appear official and to cover Mustang Panda’s personal infrastructure. Utilizing this public dealer additionally offers resiliency; the service is unlikely to be taken down due to its many official 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 subjects 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 speculate the time and sources 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 subjects 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 instrument is detected, server2 and v2 are respectively changed with server0 and v0. That is seemingly so as to keep away from tipping off defenders by solely 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’ll 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 needs to problem a command, it publishes a message to the shopper’s distinctive subject. The plaintext content material of this message is solely 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 normal output is distributed again, the server is not going to 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 kind of redirection is carried out.

Duties 2 and three: Copying the malware

The second and third duties are pretty comparable 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 at all times positioned within the C:userspublic listing.

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

Process 4: Establishing persistence

Persistence is established by the fourth job, which creates a brand new worth qvlc set to c:userspublicvcall.exe beneath the HKCUSoftwareMicrosoftWindowsCurrentVersionRun registry key. It will trigger the malware to be executed on startup.

When MQsTTang is executed on startup as c:userspublicvcall.exe, solely the C&C communication job 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 in keeping with the group’s different campaigns that concentrate on European political entities.

This new MQsTTang backdoor offers 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 expertise stacks for its instruments. It stays to be seen whether or not this backdoor will turn into a recurring a part of the group’s arsenal, however it’s yet another instance of the group’s quick improvement and deployment cycle.

IoCs

Recordsdata

Community

Github repositories

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

MITRE ATT&CK methods

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