Colin Mc Hugo

0 %
Colin Mc Hugo
Security Engineer Manager & CEO at Quantum Infinite Solutions Group Ltd.
  • Residence:
  • County:
  • Country:
Cyber Security Incident Response
Management & Architecture of Cyber Security Teams
Solutions & Coaching
  • Cyber Security Incident Response
  • Management & Architecture of Cyber Security Teams
  • Solutions
  • Training & Coaching

Operation StealthyTrident: corporate software under attack

January 28, 2021

LuckyMouse, TA428, HyperBro, Tmanger and ShadowPad linked in Mongolian supply-chain assault

UPDATE (December 14, 2020): Now we have no purpose to imagine that Ready Desktop updates or trojanized installers are nonetheless getting used to distribute malware. The final occasion we noticed occurred in July 2020 as described in our blogpost. 

On December eleventh, Ready Smooth acknowledged in an electronic mail to us that the trojanized installers and Ready Desktop’s updates haven’t been used for the reason that incident was reported to them. Additionally they acknowledged that, as a precaution in opposition to additional assaults, Ready Smooth halted the Ready Desktop updates, and that the final incidence they noticed of such assaults was in July 2020. 

ESET has no data that enables us to corroborate or dispute these statements. 

ESET researchers found that chat software program referred to as Ready Desktop, a part of a enterprise administration suite widespread in Mongolia and utilized by 430 authorities businesses in Mongolia (in line with Able), was used to ship the HyperBro backdoor (generally utilized by LuckyMouse)the Korplug RAT (often known as PlugX), and a RAT referred to as Tmanger (which was first documented by NTT Security and was used throughout Operation Lagtime IT marketing campaigns attributed to TA428 by Proofpoint). A connection with the ShadowPad backdoor, which is now utilized by at the least 5 totally different risk actors, was additionally discovered. 

Two totally different trojanized installers, as nicely as a possible compromised replace system, had been used to ship the payloadstheReadyreplace system has beensince at the least 2020 and trojanized installers delivered since at least May 2018. 

Moreover, yesterday, Avast printed a blogpost documenting a campaign targeting government agencies and a national data center in Mongolia. Throughout that marketing campaign, the attackers compromised an unknown firm that was offering authorities establishments in East Asia and leveraged that compromise to ship HyperBro by electronic mailWe imagine that compromised firm was Ready, because the filename used in that malicious electronic mail attachment is in all probability AbleTimeAccess_Update.exeand we noticed such file being used to drop the identical HyperBro pattern as described in Avast’s blogpost. 

A diagram summarizing the connections between LuckyMouse, TA428 and the ShadowPad backdoor C&C infrastructure is proven in Determine 1.

Determine 1. Abstract of the connections between LuckyMouse, TA428 and the ShadowPad backdoor

Concerning the attribution of Operation StealthyTrident, contemplating that HyperBro is often attributed to LuckyMouse, that Tmanger was attributed to TA428 and that it makes use of one of many ShadowPad C&C servers, a number of competing hypotheses exist: 

  • LuckyMouse has entry to Tmanger and ShadowPad. 
  • LuckyMouse share its entry to the compromised Ready Desktop replace server with the TA428 group or some different group getting access to Tmanger. 
  • HyperBro is now shared with TA428 or some different group getting access to Tmanger and ShadowPad. 
  • LuckyMouse and TA428 are subgroups of the identical risk actor. 

Though initially solely identified for use by the Winnti Group, it also needs to be famous right here that since at the least October 2019, ShadowPad has been shared amongst a number of risk actors together with the Winnti GroupCactusPeteTICKIceFog and KeyBoy. 

Further components relating to the connection between Tmanger and TA428 will likely be printed in a second blogpost documenting one other marketing campaign the place the attackers used each Tmanger and ShadowPad. 

We referred to as this marketing campaign Operation StealthyTrident as a result of the attackers make intensive use of a three-pronged “trident side-loading approach. 

Compromised Ready Desktop  

Ready Desktop is chat software program included as part of the Ready enterprise administration suite used in Mongolia. It’s a Chromium-based JavaScript app making use of the NodeJS library. According to Able, their software program suite is utilized by 430 authorities agencies in Mongolia. 

In mid-2018, we noticed a primary incidence of the legitimate Able Desktop utility being used to download and execute HyperBro. HyperBro is a backdoor generally attributed to LuckyMouse (often known as Emissary Panda or APT27). Ready Desktop was additionally used to obtain and execute Tmanger; in that case, the Ready Desktop software program itself was not trojanized (i.e. it did not comprise malicious code). The most certainly speculation is that the Ready Desktop replace system was compromised. 

Along with authentic Ready Desktop utilitys used to drop and execute HyperBro, likely utilizing its replace system, we additionally discovered two Ready Desktop installers that had been truly trojanized and compriseed the HyperBro backdoor and the Korplug RAT. The primary incidence of this trojanized Ready Desktop installer dates again to December 2017. A timeline of these occasions is proven in Determine 2. 

Determine 2. Timeline of the varied implants used with both a trojanized Ready Desktop installer or possible delivered by way of Ready Desktop replace

We notified Ready about these compromises. 

Ready Desktop replace mechanism 

To replace itself, Ready Desktop downloads the replace installer by way of HTTPS. The code answerable for the replace is proven in Determine 3. 

Determine 3. JavaScript code answerable for Ready Desktop updates

The downloaded replace installer is saved to %USERPROFILE%DocumentsAbleAble Desktop.exe. As soon as downloaded, the installer is executed. Within the case of a legitimate replace installer, a brand new model of Ready Desktop will likely be put in.  We noticed, nevertheless, that beginning in mid-2018, the executable downloaded wasn’t a authentic installer, however somewhat the HyperBro backdoor. Since, in that case, the executable is not an Ready Desktop installer however plain malware, no replace set up takes place and HyperBro is executed as an alternative and Ready Desktop isn’t up to date anymore. 

A number of components assist the speculation of a compromise of the replace server: 

  • The filename and the trail used to obtain HyperBro are the filename and path utilized by the replace system. 
  • The replace is downloaded by way of HTTPS, so a maninthecenter attacokay is unlikely. 
  • HyperBro was dropped on all computer systems utilizing Ready Desktop throughout the identical timebody as earlier authentic updates. 
  • The malicious Ready Desktop.exe is dropped by the true Ready Desktop software program and never malware masquerading as Ready Desktop. 
  • No authentic updates have been put in for the reason that starting of the campaign. 

We imagine this is sufficient to state that the replace mechanism was compromised. It ought to be famous that Ready Desktop has a number of replace servers, a few of them hosted at buyer groups. Since we have now no data on which replace server was used by these victims, we don’t know whether or not Ready was compromised, or one in every of their buyer’s replace servers.  

The listing of replace servers utilized by Ready Desktop is proven iDetermine 4. We will see from that listing that Ready Desktop is indeed used by a number of authorities entities akin to the Mineral Useful resource Authority of Mongolia, the Ministry of Justice and International Affairs, the Ministry of Development and City Improvement, the Improvement Financial institution of Mongolia or the Mongolian State College of Training.

Then, in July 2020, we noticed a shift from HyperBro being delivered by the replace system to a backdoor attributed to TA428 and referred to as Tmanger. 

Trojanized Ready Desktop 

Along with HyperBro and Tmanger being downloaded by authentic Ready Desktop software program, we additionally discovered two different trojanized installersIt’s unknown to us whether or not these installers had been downloadable from the Ready web site or from one other supply.  

Ready Desktop installers, each authentic and trojanized, are 7-Zip SFX installers and usually are not signed. Within the case of trojanized installers, the authentic Ready Desktop software program is bundled with both HyperBro or Korplug. The payload and its facetloading host are packaged in a data1.dat file which is a 7-Zip SFX archive whereas Ready Desktop is packaged in information.dat file which is an Superior Installer.  The content material of the trojanized installer is summarized in Determine 5. The identical IntgStat.exe facetloading host and pcalocalresloader.dll are used in each the foundation of the Ready Desktop.exe archive and data1.dat archive. 

Determine 5. Trojanized Ready Desktop installer content material

The 7-Zip SFX installer first executes IntgStat.exe, a authentic Symantec executable, which is a DLL facetloading host used to load pcalocalresloader.dll. This DLL is used to decrypt and cargo the XOR-encoded payload saved in thumb.db. This payload, XOR encoded with 0x04, as soon as mapped into reminiscence by the payload loader, will decompress and execute an embedded, LZNT1compressed PE executable that is used trename information.dat (the authentic installer) and data1.dat (the malicious payload) as Ready Desktop.exe and data1.exe respectively, and then execute them.  

As soon as executed, the newly renamed data1.exe 7-Zip SFX archive will extract its content materials and execute the second IntgStat.exe facetloading host, which then masses pcalocalresloader.dll. Once more pcalocalresloader.dll is used to load the XOR-encoded payload saved within the thumb.db file. As earlier than,  this payload will decompress and execute an embedded LZNT1compressed PE executable, which is definitely HyperBro.  

Observe that, within the case of the Ready Desktop installer trojanized with Korplug, the identical facetloading host and DLL are used to execute data1.dat, whereas the facetloading host used to execute Korplog itself isn’t IntgStat.exehowever siteadv.exe – a authentic executable from McAfee – and the loader DLL known as siteadv.dll. Aside from this change of facetloading host, the payload supply mechanism is the identical. 


The HyperBro backdoor is LuckyMouse’s customized backdoor used since at the least 2013 and in steady growth. The variant getting used right here is much like the variant described by Palo Alto Networks and KasperskyHyperBro was delivered to victims by each the authentic Ready Desktop software program and a trojanized Ready Desktop installer. 

Related to the model used with the trojanized Ready Desktop installer, in the case of the HyperBro implant downloaded by the authentic Ready Desktopits first stage consists in a 7-Zip SFX containing: 

  • thinprobe.exe, a authentic Symantec executable used for DLL facetloading 
  • thinprobe.dllHyperBro loader 
  • thumbs.dbthe XOR-encoded payload 

HyperBro’s loader DLLthinprobe.dll, is executed by DLL facetloading utilizing the thinprobe.exe executablewhich is a authentic, signed Symantec executable. Whereas the facetloading host used with the downloaded HyperBro is totally different, the DLL used to decode and execute the thumbs.db payload is precisely the identical. 

This technique is very much like the threepronged trident assault reported by a Kaspersky researcher. Each thinprobe.exe and Intgstat.exe facetloading hosts had been beforehand utilized by LuckyMouse to load HyperBro. 

Observe, nevertheless, that contrary to beforehand documented HyperBro droppers using such a trident, the payload right here isn’t Shikata GNai encoded however XOR encoded with the worth 0x04. 

The C&C URL of the HyperBro implant used with the trojanized Ready Desktop installer is https://developer.firefoxapi[.]com/ajax, whereas the C&C URL utilized by the one downloaded by the authentic Ready Desktop is https://139.180.208[.]225/ajax.

Contemplating HyperBro’s compilation timestamps, the model used with the trojanized installer was compiled Fri Dec 08 05:22:23 2017 whereas the model downloaded by Ready Desktop was compiled Mon Mar 11 03:23:54 2019. This means that the trojanized installer was used earlier than the version downloaded by the Ready Desktop replacerThe trojanized installer was first seen in our telemetry in Could 2018, whereas the model downloaded by Ready Desktop was first seen in June 2020 (see the timeline iDetermine 2).  


The Korplug RAT (often known as PlugXis utilized by a number of totally different risk teams. In this case, it was solely delivered by way of the trojanized Ready Desktop installer and we have now seen no incidence of Korplug being downloaded by authentic Ready Desktop software program. 

As mentioned beforehand, and much like installers trojanized with HyperBroKorplug is bundled in the installer with the authentic Ready Desktop and executed twice by way of the trident mannequin by DLL facetloading utilizing IntgStat.exe as host executable after which siteadv.exe. The an identical DLL is used to decode and execute the thumbs.db XOR-encoded payload because the one used with the installer trojanized with HyperBro, offering a powerful hyperlink between these two trojanized installers. 

The C&C handle utilized by Korplug is 45.77.173[.]124:443. Curiously, this handle was additionally used by a CobaltStrike implant targeting a school in Mongolia during the same timeframe. 

Its compilation timestamp (Solar Dec 08 06:22:34 2019in addition to the compilation timestamp of the installer (Wed Sep 04 16:52:04 2019) counsel that it was used after the Ready Desktop installer trojanized with HyperBro and earlier than HyperBro was downloaded by authentic Ready Desktop software program. See the timelinin Determine 2. 


Tmanger is a RAT that was first documented by NTT Security and that was used in Operation Lagtime IT which was attributed to TA428 by Proofpoint. It’s referred to as Tmanger as a result of it iapparently the title given by its developer, as we are able to see from its PDB path, for instance: 

c:userswastondesktop20190403_tmanger20191118 tm_new 1.0releasemloaddll.pdb 

Contemplating the variant we noticed throughout Operation StealthyTrident no PDB path was current but it surely is nonetheless very much like the one documented by NTT Security of their blogpost. For instance of similarity between the 2 patternsthe connection process utilized by one in every of the Tmanger patterns documented by NTT Security (14140782A68FF20000C7E9F58336620A65D4D168) and the one dropped by Ready Desktop are proven side-by-side iDetermine 6.

Determine 6. Comparability of the connection routine in Tmanger pattern dropped by authentic Ready Desktop (left) and one of many samples documented by NTT SecurityOne notable distinction is that within the case of the Ready Desktop variant, Tmanger is packaged is one single executable, whereas the variant described by NTT Safety consists of three DLLs.

ESET telemetry reveals the primary obtain of this Tmanger variant by the authentic Ready Desktop software program in July 2020. Tmanger changed HyperBro on that system and HyperBro was not seen downloaded to it after that. 

The C&C addresses utilized by this Tmanger implant, downloaded by Ready Desktop, are saved in an RC4-encrypted configuration and are the next: 

  • 45.77.55[.]145:80 
  • 45.77.55[.]145:443 
  • 45.77.55[.]145:8080 

The communication protocol is TCP and the messages are RC4 encrypted. 

Curiously, the primary handle is a part of the ShadowPad community infrastructure and, to the most effective of our data, none of these addresses are overlapping with LuckyMouse infrastructure. 


ESET Analysis found a marketing campaign focusing on Mongolian organizations that relied on compromised Ready Desktop installers and compromises to the Ready replace system to ship HyperBro, Korplug and Tmanger malware. 

This marketing campaign reveals a reference to the ShadowPad againdoor, as we noticed community infrastructure overlaps between the ShadowPad C&C community infrastructure and one of many Tmanger C&C handlees. 

Aside from the usage of HyperBrodeveloped and generally utilized by LuckyMouse, we discovered no vital overlap with the LuckyMouse toolset or community infrastructure. Does this imply that LuckyMouse has entry to ShadowPad and Tmanger or did LuckyMouse share their entry to a compromised Ready Desktop replace server with the TA428 group? One other speculation may very well be that, equally to ShadowPad, HyperBro inow shared with different risk actors. Lastly, one final speculation may very well be that LuckyMouse and TA428 are carefully associated risk actors or are truly the identical. 

Indicators of Compromise can be discovered on GitHub. For any inquiries, or to make pattern submissions associated to the topic, contact us at: [email protected]. 


The creator wish to thank Matthieu Faou, who contributed to this analysis. 


ESET detection names 


Trojanized Ready Desktop 


Payload loader 








C&C domains 


C&C IP addresses 




MITRE ATT&CK methods 

Observe: This desk was constructed utilizing version 8 of the MITRE ATT&CK framework. 

Tactic  ID  Identify  Description 
Preliminary Entry  T1195.002 Provide Chain Compromise: Compromise Software program Provide Chain  One of many Ready replace servers was possible compromised with a view to deploy HyperBro and Tmanger. 
Execution  T1204.002 Person Execution: Malicious File  Ready Desktop trojanized installer is executed by the person. 
Persistence  T1574.002 Hijack Execution Stream: DLL Aspect-Loading  HyperBro, Korplug and Tmanger are executed by way of DLL side-loading. 
Protection Evasion  T1140 Deobfuscate/Decode Recordsdata or Data  HyperBro and Korplug payloads are XOR encoded. 
Tmanger configuration is RC4 encrypted. 
T1574.002 Hijack Execution Stream: DLL Aspect-Loading  HyperBro and Korplug side-loading hosts are authentic, signed executables from trusted safety distributors. 
Assortment  T1056.001 Enter Seize: Keylogging  Tmanger helps keylogging. 
T1113 Display screen Seize  Tmanger helps display seize. 
Command And Management  T1573.001 Encrypted Channel: Symmetric Cryptography  Tmanger messages are RC4 encrypted. 
T1008 Fallback Channels  Tmanger can fallback to a secondary C&C. 
T1095 Non-Software Layer Protocol  Tmanger communicates utilizing uncooked TCP. 
T1071.001 Software Layer Protocol: Internet Protocols  HyperBro communication protocol is HTTP. 
Exfiltration  T1041 Exfiltration Over C2 Channel  Tmanger can exfiltrate recordsdata by way of a devoted command. 

Posted in SecurityTags:
Write a comment