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

ESET researchers tease apart MQsTTang, a brand new backdoor utilized by Mustang Panda, which communicates by way of the MQTT protocol

ESET researchers have analyzed MQsTTang, a new customized backdoor that we attribute to the Mustang Panda APT group. This backdoor is a part of an ongoing 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 present households or publicly obtainable 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 normal techniques, MQsTTang has only a single stage and doesn’t use any obfuscation methods.


We’ve seen unknown entities in Bulgaria and Australia in our telemetry. We even have info indicating that this marketing campaign is concentrating on a governmental establishment in Taiwan. Nevertheless, because of the nature of the decoy filenames used, we consider that political and governmental organizations in Europe and Asia are additionally being targeted. This might also be consistent with the concentrating on of the group’s other current 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 increased its activity in Europe even additional, since Russia’s invasion of Ukraine. Figure 1 exhibits our view of the concentrating on for this campaign.

Figure 1. Map displaying recognized and suspected targets of MQsTTang


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

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

One of the servers used within the present marketing campaign was operating a publicly accessible nameless FTP server that appears to be used to stage tools and payloads. In the /pub/god directory of this server there are multiple Korplug loaders, archives, and instruments that have been used in previous 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.

A few of the infrastructure used on this campaign also matches the network fingerprint of previously recognized Mustang Panda servers.

Technical analysis

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 present some fascinating characteristics. 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 used in many publicly documented malware families. One such example is Chrysaor, also referred to as Pegasus for Android. From an attacker’s perspective, one in every of MQTT’s benefits is that it hides the rest of their infrastructure behind a broker. Thus, the compromised machine never communicates instantly with the C&C server. As seen in Figure 2, this functionality is achieved through the use of 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. Using the Qt framework for malware improvement can also be pretty unusual. Lazarus’s MagicRAT is likely one of the uncommon lately documented examples.

Determine 2. RTTI displaying courses from the QMQTT library

MQsTTang is distributed in RAR archives which only include a single executable. These executables often have names related to Diplomacy and passports comparable to:

  • CVs Amb Officer PASSPORT Ministry Of Overseas Affairs.exe
  • Documents 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 associated area identify. This reality, together with the filenames, leads us to consider that the malware is spread by way of spearphishing.

To date, we’ve got solely observed a couple of samples. Apart from variations in some constants and hardcoded strings, the samples are remarkably comparable. The one notable change is the addition of some anti-evaluation methods in the latest variations. The first of those consists of utilizing the CreateToolhelp32Snapshot Windows API perform to iterate via operating processes and look for the next recognized debuggers and monitoring tools.

  • 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, while 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 recognized evaluation tools:

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

When executed instantly, 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 specific values, sure duties can be executed. Word that the exact values range between samples; the ones mentioned under correspond to the sample with SHA-1 02D95E0C369B08248BFFAAC8607BBA119D83B95B. Nevertheless, the duties themselves and the order by which they are executed is fixed.

Determine three exhibits an summary of this conduct along with the tasks which are executed when the malware is first run.

Figure 3. Execution graph displaying the subprocesses and executed tasks

Desk 1 accommodates an inventory of the duties and the value at which every of them is executed. We’ll describe them in further detail within the upcoming paragraphs.

Desk 1. Duties executed by the backdoor

Activity quantity Argument value 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 software or debugger is detected utilizing the methods we described beforehand, the conduct of process 1 is altered and duties 2, 3, and 4 are skipped totally.

Process 1: C&C communication

As was beforehand mentioned, MQsTTang communicates with its C&C server over the MQTT protocol. All noticed samples use three.228.fifty four.173 as dealer. This server is a public broker operated by EMQX, who additionally occur to be the maintainers of the QMQTT library. This could possibly be a option to make the network visitors seem reputable and to hide Mustang Panda’s own infrastructure. Using this public dealer additionally offers resiliency; the service is unlikely to be taken down because of its many authentic customers and, even when the current C&C servers are banned or taken down, Mustang Panda might spin up new ones and use the same MQTT subjects without disrupting MQsTTang’s operation.

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

As shown in Determine four, the malware and C&C server use two MQTT subjects for their communication. The first one, iot/server2, is used for communication from the shopper to the server. The second one is used for communication from the server to the shopper. It follows the format iot/v2/<Unique ID> where <Distinctive ID> is generated by taking the last eight bytes, in hex type, of a UUID. If any evaluation software is detected, server2 and v2 are respectively replaced with server0 and v0. This is doubtless with a view to keep away from tipping off defenders by totally aborting the malware’s execution early.

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

All communication between the server and the shopper uses the same encoding scheme. The MQTT message’s payload is a JSON object with a single attribute named msg. To generate the value of this attribute, the precise content material is first base64 encoded, then XORed with the hardcoded string nasa, and base64 encoded again. We’ll describe the exact format of those payloads within the relevant 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 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 matter. The plaintext content of this message is just the command to be executed. As shown in Figure 5, the shopper executes the acquired command using QProcess::startCommand from the Qt framework. The output, obtained using QProcess::readAllStandardOutput, is then despatched back in a JSON object with the next format:

Figure 5. Execution of acquired commands utilizing the QProcess class

Since only the content of ordinary output is shipped back, the server won’t 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 type of redirection is carried out.

Tasks 2 and three: Copying the malware

The second and third tasks 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 each pattern, however they are all the time situated in the C:userspublic listing.

In the second activity, the newly created copy is then launched with the command line argument ninety seven.

Activity four: Establishing persistence

Persistence is established by the fourth process, which creates a new value qvlc set to c:userspublicvcall.exe underneath the HKCUSoftwareMicrosoftWindowsCurrentVersionRun registry key. This can cause the malware to be executed on startup.

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


The Mustang Panda marketing campaign described in 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 focus on European political entities.

This new MQsTTang backdoor supplies a sort of distant shell with none of the bells and whistles related to the group’s other malware families. Nevertheless, it exhibits that Mustang Panda is exploring new know-how stacks for its tools. It remains to be seen whether this backdoor will turn into a recurring part of the group’s arsenal, but it’s another instance of the group’s quick improvement and deployment cycle.

ESET Research provides personal APT intelligence studies and knowledge feeds. For any inquiries about this service, visit the ESET Menace Intelligence web page.



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 Overseas Affairs.exe Win32/Agent.AFBI MQsTTang backdoor.
F1A8BF83A410B99EF0E7FDF7BA02B543B9F0E66C Documents.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 Documents 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 Recognized Mustang Panda Korplug loader.
61A2D34625706F17221C1110D36A435438BC0665 breakpad.dll Win32/Korplug.UB Recognized Mustang Panda Korplug loader.
30277F3284BCEEF0ADC5E9D45B66897FA8828BFD coreclr.dll Win32/Agent.ADMW Recognized Mustang Panda Korplug loader.
BEE0B741142A9C392E05E0443AAE1FA41EF512D6 HPCustPartUI.dll Win32/Korplug.UB Recognized Mustang Panda Korplug loader.
F6F3343F64536BF98DE7E287A7419352BF94EB93 HPCustPartUI.dll Win32/Korplug.UB Recognized Mustang Panda Korplug loader.
F848C4F3B9D7F3FE1DB3847370F8EEFAA9BF60F1 libcef.dll Win32/Korplug.TX Recognized Mustang Panda Korplug loader.


IP Area Internet hosting supplier First seen Details
three.228.54.173, Inc. 2020-03-26 Reliable public MQTT dealer.
eighty.85.156[.]151 N/A Chelyabinsk-Signal LLC 2023-01-05 MQsTTang supply server.
80.eighty five.157[.]three N/A Chelyabinsk-Sign LLC 2023-01-16 MQsTTang delivery server. hundred forty four.31[.]86 N/A Abuse-C Position 2023-01-22 MQsTTang delivery server.

Github repositories

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

MITRE ATT&CK methods

This table was constructed using version 12 of the MITRE ATT&CK framework.

Tactic ID Identify Description
Useful resource Improvement T1583.003 Acquire Infrastructure: Virtual Personal Server Some servers used in the campaign are on shared hosting.
T1583.004 Purchase Infrastructure: Server Some servers used in the campaign seem to be exclusive to Mustang Panda.
T1587.001 Develop Capabilities: Malware MQsTTang is a custom backdoor, in all probability developed by Mustang Panda.
T1588.002 Acquire Capabilities: Software A number of respectable and open- supply tools, together with psexec, ps, curl, and plink, have been found on the staging server.
T1608.001 Stage Capabilities: Add Malware MQsTTang was uploaded to the online server for distribution.
T1608.002 Stage Capabilities: Add Software A number of instruments have been uploaded to an FTP server.
Preliminary Access T1566.002 Phishing: Spearphishing Link MQsTTang is distributed by way of spearphishing hyperlinks to a malicious file on an attacker-controlled net server.
Execution T1106 Native API MQsTTang uses the QProcess class from the Qt framework to execute instructions.
T1204.002 Consumer Execution: Malicious File MQsTTang depends on the consumer to execute the downloaded malicious file.
Persistence T1547.001 Boot or Logon Autostart Execution: Registry rush Keys / Startup Folder MQsTTang persists by creating a registry speed key.
Defense Evasion T1036.004 Masquerading: Masquerade Activity or Service In most samples, the registry key’s created with the identify qvlc. This matches the identify of a official executable used by VLC.
T1036.005 Masquerading: Match Respectable Identify or Location When creating copies, MQsTTang makes use of filenames of professional packages.
T1480 Execution Guardrails MQsTTang checks the paths it is executed from to determine which tasks to execute.
T1622 Debugger Evasion MQsTTang detects operating debuggers and alters its conduct if any are found to be present.
Command and Management T1071 Software Layer Protocol MQsTTang communicates with its C&C server utilizing the MQTT protocol.
T1102.002 Net Service: Bidirectional Communication MQsTTang uses a authentic public MQTT dealer.
T1132.001 Knowledge Encoding: Commonplace 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 using a repeating XOR key.
Exfiltration T1041 Exfiltration Over C2 Channel The output of executed commands is shipped back to the server using the identical protocol.

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