February 7, 2025

On this blogpost, we offer a technical evaluation of CloudScout, a post-compromise toolset utilized by Evasive Panda to focus on a authorities entity and a spiritual group in Taiwan from 2022 to 2023. The CloudScout toolset is able to retrieving knowledge from numerous cloud companies by leveraging stolen net session cookies. Via a plugin, CloudScout works seamlessly with MgBot, Evasive Panda’s signature malware framework.

Key factors of this blogpost:

  • The CloudScout toolset was detected in Taiwan, between 2022 and 2023, within the community of a spiritual establishment and at a authorities entity.
  • CloudScout makes use of stolen cookies, offered by MgBot plugins, to entry and exfiltrate knowledge saved at numerous cloud companies.
  • We analyzed three CloudScout modules, which purpose to steal knowledge from Google Drive, Gmail, and Outlook. We consider that at the least seven extra modules exist.
  • Hardcoded fields in CloudScout’s net requests for stealing Outlook e-mail messages recommend that the samples concerned had been crafted to focus on Taiwanese customers.
  • Every CloudScout module, programmed in C#, is deployed by an MgBot plugin, programmed in C++.

Evasive Panda profile

Evasive Panda (also referred to as BRONZE HIGHLAND, Daggerfly, or StormBamboo) is a China-aligned APT group, working since at least 2012. Evasive Panda’s goal is cyberespionage towards international locations and organizations opposing China’s pursuits via independence actions corresponding to these within the Tibetan diaspora, non secular and educational establishments in Taiwan and in Hong Kong, and supporters of democracy in China. At instances now we have additionally noticed its cyberespionage operations prolong to international locations corresponding to Vietnam, Myanmar, and South Korea.

Evasive Panda has amassed a formidable record of assault vectors. We’ve seen its operators conduct subtle TTPs corresponding to supply-chain and watering-hole assaults, and DNS hijacking; as well as, they’ve abused the newest CVEs affecting Microsoft Workplace, Confluence, and net server purposes. The group additionally demonstrates a powerful functionality for malware growth, which is showcased in its deep assortment of multiplatform backdoors for Home windows, macOS, and Android. For Home windows, its most-used instruments are MgBot (since 2012; a {custom} malware framework consisting of a principal implant and eight at the moment recognized plugins as detailed in our WLS blogpost) and the extra lately developed Nightdoor (described in one other WLS blogpost; a feature-rich backdoor that makes use of public cloud companies for C&C communications).

Overview

In early 2023, we detected Evasive Panda deploy three beforehand unknown .NET modules (internally named CGD, CGM, and COL) at a authorities entity in Taiwan. These modules are designed to entry public cloud companies corresponding to Google Drive, Gmail, and Outlook by hijacking authenticated net periods. This system depends on stealing cookies from an internet browser database, then utilizing them in a selected set of net requests to realize entry to cloud companies. In contrast to stolen credentials, which can be blocked by safety features corresponding to two-factor authentication (2FA) and IP monitoring, stolen net session cookies permit the attacker to retrieve knowledge saved within the cloud, proper from the sufferer’s machine. In 2023, Google launched the Device Bound Session Credentials (DBSC) undertaking on GitHub and, in 2024, the App-Bound Encryption characteristic within the Chrome 127 replace. These are protecting measures towards cookie-theft malware, corresponding to CloudScout, and will doubtlessly render this toolset out of date.

Additional code evaluation of the three modules reveals an underlying growth framework, codenamed CloudScout by its builders. On this blogpost, we offer an in depth evaluation of this modular framework programmed in C#. To the very best of our information, the CloudScout toolset has not beforehand been documented publicly.

Victimology

In keeping with ESET telemetry, CloudScout was noticed in two incidents focusing on Taiwan:

  • In Could 2022, the community of a Taiwanese non secular establishment was compromised with MgBot and Nightdoor. On this incident, MgBot was used to put in a plugin that deploys a CloudScout module.
  • In February 2023, CloudScout modules and the Nightdoor implant had been detected at what we suspect is a Taiwanese authorities entity.

Moreover, we present in some hardcoded HTTP requests the inclusion of Taipei Normal Time because the time zone and zh-CN because the language pack (as proven in Determine 1). Each recommend that these samples had been crafted to focus on Taiwanese customers.

Determine 1. HTTP request from COL to Outlook Net Entry

Technical evaluation

CloudScout is a .NET malware framework consisting of a number of modules focusing on totally different cloud companies. The title CloudScout originated from the PDB paths of the modules obtained:

  • E:projectgit_newMProjectsCodeCloudScoutGoogleDriverCGDobjDebugCGD.pdb
  • E:projectgit_newMProjectsCodeCloudScoutGmailCGMobjDebugCGM.pdb
  • E:projectgit_newMProjectsCodeCloudScoutOutlookCOLobjDebugCOL.pdb

We additionally discovered point out of seven different modules within the framework (see the part CommonUtilities: The heart of CloudScout); on the time of writing, now we have not but noticed them deployed on compromised machines, hinting that the attackers deploy them selectively. Altogether, the whole record of CloudScout modules is:

  • CGD
  • CGM
  • COL
  • CTW
  • CFB
  • GMQ
  • MEXC
  • CEXC
  • CZI
  • CNE

Based mostly on the naming conference (e.g., the module focusing on Google Drive known as CGD, the one focusing on Gmail CGM, and the one focusing on Outlook COL), we infer that CTW and CFB probably goal Twitter and Fb. Nevertheless, the aim of different modules stays undetermined.

Improvement timing

The AssemblyCopyright discipline’s worth, Copyright ©  2020, within the .NET manifest of CloudScout modules, as seen in Determine 2, means that the CloudScout toolset might need been developed round 2020. Despite the fact that the legitimacy of the .NET manifest is questionable, it’s constant throughout all of the samples that we discovered. As well as, totally different variations said within the AssemblyVersion of CGD and CGM mirror the modifications added to their code base.

Figure 2. Manifest of CGD module
Determine 2. Manifest of CGD module

We additionally discovered totally different variations of the embedded inner custom-made library package deal CommonUtilities. Desk 1 exhibits totally different variations of CGD, CGM, and COL containing totally different variations of CommonUtilities.

Desk 1. Variations of CloudScout modules

Module Model SHA-1 CommonUtilities model
CGD 1.0.11 67028AEB095189FDF18B2D7B775B62366EF224A9 1.0.08
1.0.14 B3556D1052BF5432D39A6068CCF00D8C318AF146 1.0.10
1.0.17 84F6B9F13CDCD8D9D15D5820536BC878CD89B3C8 1.0.11
CGM 1.0.11 4A5BCDAAC0BC315EDD00BB1FCCD1322737BCBEEB 1.0.08
1.0.13 C058F9FE91293040C8B0908D3DAFC80F89D2E38B 1.0.10
1.0.14 621E2B50A979D77BA3F271FAB94326CCCBC009B4 1.0.11
COL 1.0.10 93C1C8AD2AF64D0E4C132F067D369ECBEBAE00B7 1.0.08

Assuming that the .NET manifest is correct, in 2020 alone, we noticed three new toolsets from Evasive Panda. The opposite two situations are the primary look of Nightdoor and a brand new UDP variant of MgBot (succeeding the UDT variant).

Outdated canine, new tips

From a standard RC4 encryption key shared by the three modules, we carried out a retrohunt and found that CGM was deployed by an MgBot plugin referred to as Gmck.dll, which was programmed in C++. The plugin was detected in an incident in 2022 the place two machines from the aforementioned non secular establishment in Taiwan had been compromised by Evasive Panda. In that incident (illustrated in Determine 3), MgBot put in the CGM module, which in flip accessed the sufferer’s Gmail account to obtain emails and private data.

Figure 3. Compromise chain
Determine 3. Compromise chain noticed within the aforementioned community of a spiritual establishment in Taiwan

Gmck.dll (which we’ll seek advice from as Gmck) carries the .NET module CGM inside its binary. With a purpose to execute CGM, Gmck first drops the module to disk at a hardcoded path, then begins the widespread language runtime (CLR) utilizing ICLRMetaHost and ICLRRuntimeHost. Lastly, it calls ExecuteInDefaultAppDomain with a reference to CGM’s entry level operate (ModuleStart), as seen in Determine 4.

Figure 4. Code to load the CGM DLL
Determine 4. Code to load the CGM DLL

In keeping with our telemetry, CGD and COL modules are additionally written to the identical staging folder, as proven in Desk 2.

Desk 2. Paths the place CloudScout modules are deployed

MgBot plugin Deployment path CloudScout module
Gmck.dll %ProgramDatapercentNVIDlAgmckmsvc_4.dll CGM
N/A %ProgramDatapercentNVIDlAolckmsvc_4.dll COL
N/A %ProgramDatapercentNVIDlAdankdhmsvc_4.dll CGD

The staging folder NVIDlA is purposely misspelled utilizing a easy homograph: it’s all in uppercase letters besides that the letter after the D is a lowercase letter el. The subfolders (as highlighted) appear to be named after the MgBot plugins. Sadly, now we have been unable to acquire the olck and dankdh plugins.

After the CGM module is efficiently deployed, the Gmck plugin wants to offer browser cookies to CGM within the type of a configuration file. Gmck extracts these cookies from net browser database information listed in Desk 3. With the discharge of App-Bound Encryption in Chrome 127 and Edge 128, Gmck is not capable of decrypt Cookies database information from Chrome and Edge.

Desk 3. Database information from which Gmck extracts cookies

Focused browser Database information
Chrome %localappdatapercentGoogleChromeUser DataLocal State
%localappdatapercentGoogleChromeUser Information<username>NetworkCookies
Edge %localappdatapercentMicrosoftEdgeUser DataLocal State
%localappdatapercentMicrosoftEdgeUser Information<username>NetworkCookies
Firefox %AppDatapercentMozillaFirefoxprofiles.ini
%AppDatapercentMozillaFirefox<profile_name>cookies.sqlite

The configuration file will need to have a .dat extension and be RC4 encrypted utilizing the important thing 0dda5a8d⁠-⁠e4c2⁠-⁠477d⁠-⁠85df⁠-⁠fcb611a62ffe with a purpose to be acknowledged by CGM. This RC4 key’s utilized by all three CloudScout modules to decrypt the configuration information, which implies the MgBot plugins should additionally use this key for encryption.

Determine 5 summarizes the connection between Gmck and CGM.

Figure 5. Interactions between Gmck and CGM
Determine 5. Interactions between Gmck and CGM

Configuration

The configuration file cm_cke_<yyyyymmdd>_<hhmmss>.dat in Determine 5 is offered by the MgBot plugin after it extracts cookies from an internet browser’s database. The CloudScout module obtains a brand new configuration by constantly monitoring its working listing, on the lookout for information with .dat extensions. For every .dat file that it finds, the CloudScout module spawns a brand new thread to deal with the file, which implies it may possibly deal with a number of configuration information on the similar time. The newly spawned thread handles a full assortment cycle, from parsing the configuration to downloading all of the focused knowledge. On the finish of the cycle, the configuration file is faraway from disk to stop by accident repeating the identical cycle.

The configuration file is in JSON format. It incorporates two principal knowledge constructions: token and config. The token construction incorporates the cookies organized by area title. And config incorporates settings for downloading and staging the collected knowledge for exfiltration, in addition to for protecting this system working or exiting after a profitable cycle (dealone discipline). An instance of a configuration file is included in Determine 6.

Figure 6. An example of a configuration generated by the Gmck plugin for the CGM module
Determine 6. An instance of a configuration generated by the Gmck plugin for the CGM module

CommonUtilities: The guts of CloudScout

On the coronary heart of CloudScout is the CommonUtilities package deal, which supplies all crucial low-level libraries for the modules to run, as illustrated in Determine 7. This package deal is saved within the assets part of CloudScout modules and is loaded at first of the ModuleStart operate.

Figure 7. Overview of the design of CommonUtilities
Determine 7. Overview of the design of CommonUtilities

As seen in Determine 8, the .NET manifest of CommonUtilities reveals all of its consumer modules.

Figure 8. Manifest of CommonUtilities
Determine 8. Manifest of CommonUtilities

CommonUtilities incorporates fairly just a few custom-implemented libraries regardless of the ample availability of comparable open-source libraries on-line. These {custom} libraries give the builders extra flexibility and management over the interior workings of their implant, in comparison with open-source options. In addition they manifest sure unpredictable behaviors that pressured us to dig deep into the code to grasp. Examples of those {custom} libraries are HTTPAccess and ManagedCookie.

HTTPAccess supplies crucial features to deal with all of the HTTP communications of CloudScout modules. It has the potential of modifying HTTP headers, as proven in Determine 9.

Figure 9. Code in HTTPAccess to modify HTTP headers
Determine 9. Code in HTTPAccess to switch HTTP headers

As highlighted on this code snippet, the this.mngCk object, an occasion of the ManagedCookie class, is used to combine cookies into the crafted HTTP headers. Because the title suggests, ManagedCookie supplies features to handle cookies for net requests between CloudScout and focused cloud companies. What makes this class particular is its complete record of cookie parsers able to turning most cookies into default .NET cookie objects. Determine 10 exhibits the totally different regexes created to match numerous combos of attribute-value pairs in cookies.

Figure 10. Different regexes to handle various combinations of attribute-value pairs in cookies
Determine 10. Totally different regexes to deal with numerous combos of attribute-value pairs in cookies

The body of CloudScout

All CloudScout modules share a uniform structure, as proven in Determine 11. The core performance of the module is within the Cloud namespace, which is almost similar in every module. The implementation solely diverges in features associated to authentication and knowledge retrieval, the place every module must generate particular net requests or to parse sure net responses in keeping with the cloud service it targets.

Figure 11. Common design shared by three CloudScout modules
Determine 11. Widespread design shared by three CloudScout modules

The streamlined design of CloudScout and the core logic of the Cloud namespace is illustrated in Determine 12.

Figure 12. Overview of the design of a CloudScout module
Determine 12. Overview of the design of a CloudScout module

Authentication

Cookies typically usually are not very properly documented by net platforms. Authentication cookies are likely to have brief lifespans and are continuously up to date because the consumer interacts with the platform by way of an internet browser. Nevertheless, so long as the periods are nonetheless legitimate, the cookies listed in Desk 4 might be abused by CloudScout to entry and obtain worthwhile knowledge from cloud companies.

Desk 4. Authentication cookies dealt with by the CloudScout modules

Service Area Required cookies
Google Drive drive.google.com
accounts.google.com
OSID, HSID, SID, SSID, APISID, SAPISID, LSID
Gmail mail.google.com
accounts.google.com
Outlook outlook.reside.com
login.reside.com
X-OWA-CANARY, RPSSecAuth, ClientId

X-OWA-CANARY is a safety cookie utilized by Microsoft Outlook Net Entry (OWA) to stop cross-site request forgery assaults. It’s assigned at first of every session when the consumer is authenticated. CloudScout’s COL module implements a mechanism to retrieve this cookie when it isn’t out there, by establishing a brand new session utilizing the RPSSecAuth and ClientId cookies to reauthenticate, as proven in Determine 13.

Figure 13. Code to get the X-OWA-CANARY cookie
Determine 13. Code to get the X-OWA-CANARY cookie

Information retrieval

After authentication, the CloudScout modules browse the compromised cloud service accounts in a way just like how a daily consumer would with an internet browser. To realize this, every CloudScout module is provided with a set of hardcoded net requests to carry out, together with complicated HTML parsers, which establish and extract the info of curiosity from the online responses.

For instance, the CGM and COL modules are concerned with mail folder listings and e-mail messages, focusing on Gmail and Outlook, respectively. Determine 14 exhibits the steps that CGM performs to extract e-mail headers, e-mail our bodies, and attachments from the HTML content material served by the Gmail net server.

Figure 14. Code to parse an HTML page to extract email message data
Determine 14. Code to parse an HTML web page to extract e-mail message knowledge

Then again, CGD is concerned with consumer data from Google Drive; a full listing hierarchy; and information with extensions .doc, .docx, .xls, .xlsx, .ppt, .pptx, .pdf, and .txt. Determine 15 is the code snippet from CGD to generate a obtain URL for a doc.

Figure 15. Code to generate a download URL from Google Drive
Determine 15. Code to generate a obtain URL from Google Drive

The module appends a {custom} header to every downloaded merchandise, whether or not it’s a file or an e-mail. This tradition header contains metadata of the merchandise corresponding to consumer ID (assigned by the malware), e-mail topic, or filename, and the username of the cloud service (Desk 5). The added header almost certainly permits stolen knowledge to be processed at scale, by automated methods, for fast indexing or to carry out evaluation.

Desk 5. Customized headers for downloaded e-mail and information

Mail header File header
tasktype:
taskid:
clientid:
objectname:
mailid:
username:
topic:=?utf-8?b?<base64_encoded_data>?=
froms:=?utf-8?b?<base64_encoded_data>?=
tos:=?utf-8?b?<base64_encoded_data>?=
sort:
sourceflag: Gmail
filepath:
mailcountry:
attachment:
mailboxtype:outlook
folder:=?utf-8?b? <base64_encoded_data>?=
time: <yyyy-MM-dd HH:mm:ss>
captime: <yyyy-MM-dd HH:mm:ss>
tasktype:
taskid:
clientid:
objectname:
username:
skydrivetype:googledrive
path:=?utf-8?b? ?<base64_encoded_data>?=
supply:googledrive
filename:=?utf-8?b? ?<base64_encoded_data>?=
key:
filetime: <yyyy-MM-dd HH:mm:ss>
measurement:
sort:googledrive
captime: <yyyy-MM-dd HH:mm:ss>

After including the header, every merchandise is encrypted utilizing the identical RC4 key as used for the configuration file and saved with the filename <pseudorandom_GUID>.<{custom}_extension>, the place <custom_extension> signifies the kind of stolen knowledge, as listed in Desk 6.

Desk 6. Filename extension for every knowledge class

Information class CGD CGM or COL
Private data .pc_plug_googledrive_profile N/A
E-mail N/A .pc_plug_gmck_email
Listing itemizing .pc_plug_googledrive_filelist .pc_plug_gmck_email_list
File .pc_plug_googledrive_file N/A

Subsequent, all gadgets are compressed right into a ZIP archive named <pseudorandom_GUID>.hxkz_zip and positioned in a listing for exfiltration as specified by the datapath discipline of the configuration. This archive can later be exfiltrated by both MgBot or Nightdoor. Within the last step, the CloudScout modules do a full cleanup, eradicating all artifacts generated through the assortment cycle besides the information to be exfiltrated, earlier than checking the dealone flag to both exit or to proceed and watch for a brand new configuration file to begin a brand new assortment cycle.

Conclusion

CloudScout is a .NET toolset utilized by Evasive Panda to steal knowledge saved in cloud companies. It’s applied as an extension to MgBot and makes use of the pass-the-cookie approach to hijack authenticated periods from net browsers.

On this blogpost, now we have highlighted the skilled design behind the CloudScout framework to reveal Evasive Panda’s technical capabilities and the essential roles that cloud-stored paperwork, consumer profiles, and e-mail play in its espionage operations.

IoCs

A complete record of indicators of compromise (IoCs) and samples might be present in our GitHub repository.

Recordsdata

SHA-1 Filename Detection Description
C70C3750AC6B9D7B033ADDEF838EF1CC28C262F3 pmsrvd.dll Win32/Agent.AELQ MgBot loader.
812124B84C5EA455F7147D94EC38D24BDF159F84 pmsrvd.dll Win32/Agent.AELQ MgBot loader.
AD6C84859D413D627AC589AEDF9891707E179D6C 3.exe Win32/Agent.ADJV MgBot dropper.
3DD958CA6EB7E8F0A0612D295453A3A10C08F5FE 1.exe Win32/Agent.ADJV MgBot dropper.
547BD65EEE05D744E075C5E12FB973A74D42438F doc.exe Win32/Agent.AFXX Nightdoor dropper.
348730018E0A5554F0F05E47BBA43DC0F55795AC DJCU.dll Win32/Nightdoor.A Nightdoor loader.
9B6A473820A72111C1A38735992B55C413D941EE CommonUtilities.dll MSIL/Agent.UEK CloudScout inner library package deal model 1.0.0.
621E2B50A979D77BA3F271FAB94326CCCBC009B4 CGM.dll MSIL/CloudScout.A CloudScout Gmail stealer model 1.0.14.
C058F9FE91293040C8B0908D3DAFC80F89D2E38B CGM.dll MSIL/CloudScout.A CloudScout Gmail stealer model 1.0.13.
4A5BCDAAC0BC315EDD00BB1FCCD1322737BCBEEB CGM.dll MSIL/CloudScout.A CloudScout Gmail stealer model 1.0.18.
67028AEB095189FDF18B2D7B775B62366EF224A9 CGD.dll MSIL/CloudScout.A CloudScout Google Drive stealer model 1.0.11.
B3556D1052BF5432D39A6068CCF00D8C318AF146 CGD.dll MSIL/CloudScout.A CloudScout Google Drive stealer model 1.0.14.
84F6B9F13CDCD8D9D15D5820536BC878CD89B3C8 CGD.dll MSIL/CloudScout.A CloudScout Google Drive stealer model 1.0.17.
93C1C8AD2AF64D0E4C132F067D369ECBEBAE00B7 COL.dll MSIL/CloudScout.A CloudScout Outlook Net Entry stealer model 1.0.10.
8EAA213AE4D482938C5A7EC523C83D2C2E1E8C0E CommonUtilities.dll MSIL/CloudScout.A CloudScout inner library package deal model 1.0.8.
A1CA41FDB61F03659168050DE3E208F0940F37D8 CommonUtilities.dll MSIL/CloudScout.A CloudScout inner library package deal model 1.0.11.

Community

IP Area Internet hosting supplier First seen Particulars
103.96.128[.]44 N/A IRT⁠-⁠WUZHOUHULIAN⁠-⁠HK 2022⁠-⁠05⁠-⁠26 MgBot and Nightdoor C&C server.

MITRE ATT&CK methods

This desk was constructed utilizing version 15 of the MITRE ATT&CK framework.

Tactic ID Title Description
Useful resource Improvement T1583.004 Purchase Infrastructure: Server Evasive Panda acquired servers for the C&C infrastructure of MgBot and Nightdoor.
T1587.001 Develop Capabilities: Malware Evasive Panda developed {custom} implants corresponding to MgBot, CloudScout, and Nightdoor.
Execution T1569.002 System Providers: Service Execution MgBot is executed as a Home windows service.
T1106 Execution via API The MgBot installer makes use of Home windows APIs to create processes. Gmck makes use of ExecuteInDefaultAppDomain to execute CGM within the CLR.
Persistence T1543.003 Create or Modify System Course of: Home windows Service MgBot replaces the present Software Administration service DLL path with its personal.
Privilege Escalation T1548.002 Abuse Elevation Management Mechanism: Bypass Person Entry Management MgBot performs UAC bypass.
Protection Evasion T1140 Deobfuscate/Decode Recordsdata or Data Gmck decrypts Chrome, Edge, and Firefox net browser databases to extract cookies.
T1112 Modify Registry MgBot modifies the registry for persistence.
T1027 Obfuscated Recordsdata or Data Gmck obfuscates the configuration that incorporates cookies.
T1550.004 Use Alternate Authentication Materials: Net Session Cookie CloudScout makes use of stolen cookies to entry cloud assets.
T1036.005 Masquerading: Match Respectable Title or Location CloudScout modules are put in to %ProgramDatapercentNVIDlA to imitate an NVIDIA listing.
Credential Entry T1539 Steal Net Session Cookie Gmck steals cookies.
Discovery T1082 System Data Discovery MgBot collects system data.
Assortment T1560.001 Archive Collected Information: Archive by way of Utility CloudScout modules use SharpZipLib to compress knowledge earlier than exfiltration.
T1530 Information from Cloud Storage Object CGD downloads information saved on Google Drive.
T1114.002 E-mail Assortment: Distant E-mail Assortment CGM and COL entry and gather emails from Gmail and Outlook Net Entry, respectively.
Command and Management T1095 Non-Software Layer Protocol MgBot communicates with its C&C by way of UDP.
Exfiltration T1041 Exfiltration Over C2 Channel MgBot exfiltrates collected knowledge to its C&C.