ESET researchers tease aside MQsTTang, a brand new backdoor utilized by Mustang Panda, which communicates by way of the MQTT protocol
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 many of the group’s malware, MQsTTang doesn’t appear to be based mostly on present households or publicly out there tasks.
Mustang Panda is understood for its personalized Korplug variants (additionally dubbed PlugX) and elaborate loading chains. In a departure from the group’s typical ways, MQsTTang has solely a single stage and doesn’t use any obfuscation strategies.
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, as a result of 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 according to the focusing on of the group’s different latest campaigns. As documented by fellow researchers at Proofpoint, Mustang Panda has been recognized to focus on European governmental entities since no less than 2020 and has elevated its exercise in Europe even additional, since Russia’s invasion of Ukraine. Determine 1 exhibits our view of the focusing on for this marketing campaign.

Determine 1. Map exhibiting recognized 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 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 have been utilized in earlier Mustang Panda campaigns. This is identical 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 recognized 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 fascinating 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, often known as Pegasus for Android. From an attacker’s perspective, one in all 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 by utilizing the open supply QMQTT library. This library depends upon the Qt framework, a big a part of which is statically linked within the malware. Utilizing the Qt framework for malware improvement can be pretty unusual. Lazarus’s MagicRAT is among the uncommon just lately documented examples.

Determine 2. RTTI exhibiting lessons from the QMQTT library
MQsTTang is distributed in RAR archives which solely comprise a single executable. These executables normally have names associated to Diplomacy and passports equivalent to:
- CVs Amb Officer PASSPORT Ministry Of International Affairs.exe
- Paperwork members of delegation diplomatic from Germany.Exe
- PDF_Passport and CVs of diplomatic members from Tokyo of JAPAN.eXE
- Observe No.18-NG-23 from Embassy of Japan.exe
These archives are hosted on an online server with no related area identify. This truth, together with the filenames, leads us to imagine that the malware is unfold by way of spearphishing.
To date, we’ve solely noticed a number of samples. Moreover variations in some constants and hardcoded strings, the samples are remarkably related. The one notable change is the addition of some anti-analysis strategies 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 recognized 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
Observe 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 Lessons and Titles utilized by recognized 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. Observe that the precise values range between samples; those talked about beneath correspond to the pattern with SHA-1 02D95E0C369B08248BFFAAC8607BBA119D83B95B. Nevertheless, the duties themselves and the order during which they’re executed is fixed.
Determine 3 exhibits an outline of this habits together with the duties which might be executed when the malware is first run.

Determine 3. Execution graph exhibiting the subprocesses and executed duties
Desk 1 comprises 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
Process quantity | Argument worth | Process description |
---|---|---|
1 | 5 | Begin C&C communication. |
2 | 9 | Create copy and launch. |
3 | 32 | Create persistence copy. |
4 | 119 | Set up persistence. |
5 | 148 | Cease recursive execution. |
If any evaluation device or debugger is detected utilizing the strategies we described beforehand, the habits of process 1 is altered and duties 2, 3, and 4 are skipped completely.
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 could possibly be a method to make the community site visitors appear professional 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 professional 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 device is detected, server2 and v2 are respectively changed with server0 and v0. That is seemingly as a way 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’ll describe the precise format of those payloads within the related sections.
Upon first connecting to the dealer, the malware subscribes to its distinctive matter. Then, and each 30 seconds thereafter, the shopper publishes a KeepAlive message to the server’s matter. The content material of this message is a JSON object with the next format:
“Alive”: “<malware’s uptime in minutes>”, “c_topic”: “<shopper’s distinctive matter>”
|
When the server needs to situation a command, it publishes a message to the shopper’s distinctive matter. 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:
“c_topic”: “<shopper’s distinctive matter>”, “ret”: “<Command output>”
|

Determine 5. Execution of obtained instructions utilizing the QProcess class
Since solely the content material of ordinary output is shipped again, the server is not going to obtain errors or warnings. From the server’s viewpoint, a failed command is thus indistinguishable from a command that merely produces no output until some kind 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 situated within the C:userspublic listing.
Within the second process, the newly created copy is then launched with the command line argument 97.
Process 4: Establishing persistence
Persistence is established by the fourth process, which creates a brand new worth qvlc set to c:userspublicvcall.exe underneath the HKCUSoftwareMicrosoftWindowsCurrentVersionRun registry key. This can 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 offers a sort of distant shell with none of the bells and whistles related to the group’s different malware households. Nevertheless, it exhibits that Mustang Panda is exploring new expertise stacks for its instruments. It stays to be seen whether or not this backdoor will change into a recurring a part of the group’s arsenal, however it’s yet one more instance of the group’s quick improvement and deployment cycle.
IoCs
Recordsdata
SHA-1 | Filename | Detection | Description |
---|---|---|---|
A1C660D31518C8AFAA6973714DE30F3D576B68FC | CVs Amb.rar | Win32/Agent.AFBI | RAR archive used to distribute MQsTTang backdoor. |
430C2EF474C7710345B410F49DF853BDEAFBDD78 | CVs Amb Officer PASSPORT Ministry Of International Affairs.exe | Win32/Agent.AFBI | MQsTTang backdoor. |
F1A8BF83A410B99EF0E7FDF7BA02B543B9F0E66C | Paperwork.rar | Win32/Agent.AFBI | RAR archive used to distribute MQsTTang backdoor. |
02D95E0C369B08248BFFAAC8607BBA119D83B95B | PDF_Passport and CVs of diplomatic members from Tokyo of JAPAN.eXE | Win32/Agent.AFBI | MQsTTang backdoor. |
0EA5D10399524C189A197A847B8108AA8070F1B1 | Paperwork members of delegation diplomatic from Germany.Exe | Win32/Agent.AFBI | MQsTTang backdoor. |
982CCAF1CB84F6E44E9296C7A1DDE2CE6A09D7BB | Paperwork.rar | Win32/Agent.AFBI | RAR archive used to distribute MQsTTang backdoor. |
740C8492DDA786E2231A46BFC422A2720DB0279A | 23 from Embassy of Japan.exe | Win32/Agent.AFBI | MQsTTang backdoor. |
AB01E099872A094DC779890171A11764DE8B4360 | BoomerangLib.dll | Win32/Korplug.TH | Identified Mustang Panda Korplug loader. |
61A2D34625706F17221C1110D36A435438BC0665 | breakpad.dll | Win32/Korplug.UB | Identified Mustang Panda Korplug loader. |
30277F3284BCEEF0ADC5E9D45B66897FA8828BFD | coreclr.dll | Win32/Agent.ADMW | Identified Mustang Panda Korplug loader. |
BEE0B741142A9C392E05E0443AAE1FA41EF512D6 | HPCustPartUI.dll | Win32/Korplug.UB | Identified Mustang Panda Korplug loader. |
F6F3343F64536BF98DE7E287A7419352BF94EB93 | HPCustPartUI.dll | Win32/Korplug.UB | Identified Mustang Panda Korplug loader. |
F848C4F3B9D7F3FE1DB3847370F8EEFAA9BF60F1 | libcef.dll | Win32/Korplug.TX | Identified Mustang Panda Korplug loader. |
Community
IP | Area | Internet hosting supplier | First seen | Particulars |
---|---|---|---|---|
3.228.54.173 | dealer.emqx.io | Amazon.com, Inc. | 2020-03-26 | Legit public MQTT dealer. |
80.85.156[.]151 | N/A | Chelyabinsk-Sign LLC | 2023-01-05 | MQsTTang supply server. |
80.85.157[.]3 | N/A | Chelyabinsk-Sign LLC | 2023-01-16 | MQsTTang supply server. |
185.144.31[.]86 | N/A | Abuse-C Function | 2023-01-22 | MQsTTang supply server. |
Github repositories
- https://uncooked.githubusercontent[.]com/YanNaingOo0072022/14/essential/Paperwork.rar
- https://uncooked.githubusercontent[.]com/YanNaingOo0072022/ee/essential/CVs Amb.rar
MITRE ATT&CK strategies
This desk was constructed utilizing version 12 of the MITRE ATT&CK framework.
Tactic | ID | Identify | Description |
---|---|---|---|
Useful resource Improvement | T1583.003 | Purchase Infrastructure: Digital Personal Server | Some servers used within the marketing campaign are on shared internet hosting. |
T1583.004 | Purchase Infrastructure: Server | Some servers used within the marketing campaign appear to be unique to Mustang Panda. | |
T1587.001 | Develop Capabilities: Malware | MQsTTang is a customized backdoor, in all probability developed by Mustang Panda. | |
T1588.002 | Get hold of Capabilities: Software | A number of professional and open- supply instruments, together with psexec, ps, curl, and plink, have been discovered on the staging server. | |
T1608.001 | Stage Capabilities: Add Malware | MQsTTang was uploaded to the net server for distribution. | |
T1608.002 | Stage Capabilities: Add Software | A number of instruments have been uploaded to an FTP server. | |
Preliminary Entry | T1566.002 | Phishing: Spearphishing Hyperlink | MQsTTang is distributed by way of spearphishing hyperlinks to a malicious file on an attacker-controlled internet server. |
Execution | T1106 | Native API | MQsTTang makes use of the QProcess class from the Qt framework to execute instructions. |
T1204.002 | Person Execution: Malicious File | MQsTTang depends on the consumer to execute the downloaded malicious file. | |
Persistence | T1547.001 | Boot or Logon Autostart Execution: Registry Run Keys / Startup Folder | MQsTTang persists by making a registry Run key. |
Protection Evasion | T1036.004 | Masquerading: Masquerade Process or Service | In most samples, the registry secret is created with the identify qvlc. This matches the identify of a professional executable utilized by VLC. |
T1036.005 | Masquerading: Match Legit Identify or Location | When creating copies, MQsTTang makes use of filenames of professional packages. | |
T1480 | Execution Guardrails | MQsTTang checks the paths it’s executed from to find out which duties to execute. | |
T1622 | Debugger Evasion | MQsTTang detects operating debuggers and alters its habits if any are discovered to be current. | |
Command and Management | T1071 | Utility Layer Protocol | MQsTTang communicates with its C&C server utilizing the MQTT protocol. |
T1102.002 | Internet Service: Bidirectional Communication | MQsTTang makes use of a professional public MQTT dealer. | |
T1132.001 | Knowledge Encoding: Customary Encoding | The content material of the messages between the malware and server is base64 encoded. | |
T1573.001 | Encrypted Channel: Symmetric Cryptography | The content material of the messages between the malware and server is encrypted utilizing a repeating XOR key. | |
Exfiltration | T1041 | Exfiltration Over C2 Channel | The output of executed instructions is shipped again to the server utilizing the identical protocol. |