ESET researchers noticed a number of campaigns focusing on governmental establishments in Thailand, beginning in 2023. These assaults leveraged revamped variations of parts beforehand attributed by different researchers to the China-aligned superior persistent risk (APT) group Mustang Panda, and later, a brand new set of instruments that abuse service suppliers resembling Pastebin, Dropbox, OneDrive, and GitHub to execute instructions on compromised computer systems and exfiltrate delicate paperwork.
Primarily based on our findings, we determined to trace this exercise cluster because the work of a separate risk actor. The quite a few occurrences of the string [Bb]ectrl within the code of the group’s instruments impressed us to call it CeranaKeeper; it’s a wordplay between the phrases beekeeper and the bee species Apis Cerana, or the Asian honey bee.
Key factors of this blogpost:
ESET researchers found a brand new China-aligned risk actor, CeranaKeeper, focusing on governmental establishments in Thailand. A few of its instruments had been beforehand attributed to Mustang Panda by different researchers.
The group consistently updates its backdoor to evade detection and diversifies its strategies to help huge information exfiltration.
CeranaKeeper abuses common, respectable cloud and file-sharing providers resembling Dropbox and OneDrive to implement customized backdoors and extraction instruments.
The group makes use of GitHub’s pull request and concern remark options to create a stealthy reverse shell, leveraging GitHub, a preferred on-line platform for sharing and collaborating on code, as a C&C server.
CeranaKeeper has been lively since a minimum of the start of 2022, primarily focusing on governmental entities in Asian international locations resembling Thailand, Myanmar, the Philippines, Japan, and Taiwan; we consider it’s aligned with China’s pursuits. The group’s relentless hunt for information is exceptional, with its attackers deploying a wide selection of instruments aimed toward extracting as a lot info as doable from compromised networks. Within the operation we analyzed, the group turned compromised machines into replace servers, devised a novel approach utilizing GitHub’s pull request and concern remark options to create a stealthy reverse shell, and deployed single-use harvesting parts when amassing whole file bushes.
We briefly launched CeranaKeeper within the ESET APT Exercise Report This autumn 2023–Q1 2024, which was launched in Could 2024. On this blogpost, we describe these beforehand undocumented, customized instruments deployed by CeranaKeeper and share extra of our findings concerning the operations of this risk actor.
We offered a few of our findings about CeranaKeeper and the compromise in Thailand on the Virus Bulletin convention on October 2nd, 2024, and in our white paper, which you’ll learn in full right here. This month, Virus Bulletin will even publish our white paper about this subject on its web site.
Attribution
Whereas a few of CeranaKeeper’s actions had beforehand been attributed to Mustang Panda (aka Earth Preta or Stately Taurus) by Talos, Development Micro, and Palo Alto Networks Unit 42, we’ve determined to trace this exercise cluster because the work of CeranaKeeper. We consider CeranaKeeper makes use of the publicly documented toolset referred to as bespoke stagers (or TONESHELL), closely depends on the side-loading approach, and makes use of a selected sequence of instructions to exfiltrate recordsdata from a compromised community. Moreover, we contemplate the usage of political lures and PlugX parts to be the work of MustangPanda. Regardless of some similarities of their actions (comparable side-loading targets, archive format), we noticed distinct organizational and technical variations between the 2 teams, resembling variations of their toolsets, infrastructure, operational practices, and campaigns. We additionally famous variations in the way in which the 2 teams accomplish comparable duties.
In its operations, CeranaKeeper deploys parts generally known as TONEINS, TONESHELL, and PUBLOAD, that are distinctive to the group. The group stands out for its creativity and adaptableness in its assaults, resembling utilizing revamped variations of the aforementioned parts and new instruments that abuse providers resembling Pastebin, Dropbox, OneDrive, and GitHub. We describe these instruments within the Toolset aiding huge exfiltration part.
Moreover, the group left some metadata in its code that supplied us with insights into its improvement course of, additional solidifying our separation of the 2 teams and our attribution to CeranaKeeper. Each risk actors might depend on the identical third social gathering, resembling a provider of instruments used within the deployment part, which isn’t unusual amongst China-aligned teams, or have some stage of data sharing, which might clarify the hyperlinks that we’ve noticed. In our opinion, this can be a extra possible rationalization than a single risk actor sustaining two utterly separate units of instruments, infrastructure, operational practices, and campaigns.
Compromising machines in the identical community
The compromise vectors that CeranaKeeper used within the case we analyzed have but to be discovered. When the group obtained a foothold within the community of a Thai governmental establishment, in the midst of 2023, a compromised machine carried out brute-force assaults towards a site controller server within the native space community.
After gaining privileged entry, the attackers put in the TONESHELL backdoor, deployed a device to dump credentials, and used a respectable Avast driver and a customized software to disable safety merchandise on the machine. From this compromised server, they used a distant administration console to deploy and execute their backdoor on different computer systems within the community. Moreover, CeranaKeeper used the compromised server to retailer updates for TONESHELL, turning it into an replace server.
The group deployed a brand new BAT script throughout the community, extending its attain to different machines in the identical area by exploiting the area controller to achieve area admin privileges. This enabled CeranaKeeper to maneuver to the subsequent part of its operation and obtain the ultimate objective: huge information harvesting.
Toolset aiding huge exfiltration
After deploying their TONESHELL backdoor and performing a couple of lateral actions, it seems that the attackers discovered and chosen a couple of compromised computer systems of enough curiosity to deploy beforehand undocumented, customized instruments. These assist instruments had been used not solely to facilitate the exfiltration of paperwork to public storage providers but in addition to behave as various backdoors. The backdoors and exfiltration instruments we describe had been deployed to extremely focused machines solely.
WavyExfiller: A Python uploader abusing Dropbox and PixelDrain
The primary of a sequence of unknown parts we found in June 2023 is WavyExfiller, a Python package deal bundled into an executable utilizing PyInstaller and a direct Python implementation of the exfiltration technique described by Unit 42. We named this element WavyExfiller as a result of .wav extension of an area file that incorporates search masks for figuring out and compressing paperwork prepared for export. The PyInstaller-bundled executable is known as SearchApp.exe (SHA-256: E7B6164B6EC7B7552C93713403507B531F625A8C64D36B60D660D66E82646696).
The module has three essential capabilities: to retrieve an encrypted Dropbox token from a Pastebin web page (a web based service for storing and sharing plain textual content information), to create password-protected archives of paperwork present in customers’ directories, and to add these archives to Dropbox.
In October 2023, we noticed a variant (SHA-256: 451EE465675E674CEBE3C42ED41356AE2C972703E1DC7800A187426A6B34EFDC) saved underneath the identify oneDrive.exe. Regardless of its identify, this model makes use of the file-sharing service PixelDrain to exfiltrate the archived recordsdata. Similar to SearchApp.exe talked about above, this variant checks the C drive, which usually incorporates the working system, put in packages, and native customers’ paperwork. Moreover, oneDrive.exe makes an attempt to gather recordsdata from mapped drives, if any, starting from letter D to N (besides L) as illustrated in Determine 1, which can signify linked exterior storage gadgets like USBs and onerous drives, networked drives in an workplace surroundings, or digital drives created by particular software program. This exhibits that CeranaKeeper stepped up its stage of greediness and tried reaching different potential or recognized sources of data. Nevertheless, it’s unclear whether or not the exfiltration operation was profitable, as checking uploaded recordsdata on PixelDrain shouldn’t be doable by way of the uncovered API.
Determine 1. Traversing and amassing recordsdata from a listing of drives
DropboxFlop: A Python backdoor abusing Dropbox
In October 2023, across the similar time that we discovered the PixelDrain variant, we found a brand new PyInstaller bundled executable with SHA-256 hash DAFAD19900FFF383C2790E017C958A1E92E84F7BB159A2A7136923B715A4C94F. Plainly CeranaKeeper created it based mostly on a publicly out there mission referred to as Dropflop, which is a reverse shell with add and obtain capabilities. The compiled Python file is named dropboxflop.pyc. The backdoor retrieves an encrypted Dropbox token and depends upon recordsdata current within the distant Dropbox repository to execute instructions on the machine. It creates a singular folder regionally and generates a “heartbeat” by updating the distant file referred to as lasttime each 15 seconds. It additionally checks for a file named duties that, if discovered, is downloaded and parsed as a JSON file. There are two sorts of duties carried out: command execution and file add. As soon as accomplished, the backdoor sends the outcomes by updating the content material of the file output.
OneDoor: A C++ backdoor abusing OneDrive
A number of days after deploying the Python backdoor DropboxFlop, CeranaKeeper returned with a statically linked C/C++ backdoor abusing OneDrive that we’ve named OneDoor. The pattern (SHA-256: 3F81D1E70D9EE39C83B582AC3BCC1CDFE038F5DA31331CDBCD4FF1A2D15BB7C8) is known as OneDrive.exe. The file mimics the respectable executable from Microsoft, as proven within the properties view in Determine 2.
Determine 2. OneDoor file properties
OneDoor behaves similarly to the DropboxFlop backdoor, however makes use of the OneDrive REST API of the Microsoft Graph API to obtain instructions and exfiltrate recordsdata.
OneDoor creates a log file and makes an attempt to entry a file named config.ini. If it’s not current, OneDoor makes use of a hardcoded buffer. The file or buffer begins with a key and an initialization vector, that are used to decrypt the remainder of the information utilizing AES-128 in CBC mode. The plaintext incorporates a URL, which the malware makes use of in an HTTP GET request. The response incorporates a OneDrive token, which is utilized in subsequent requests to Microsoft OneDrive.
OneDoor additionally retrieves the ID of a folder referred to as approot, which is used to retailer software information.
Just like the config.ini file, the malware makes an attempt to entry a file named errors.log. If the file doesn’t exist, it makes use of a hardcoded buffer. The content material of the file or buffer is decrypted; the plaintext information incorporates a 1024-bit RSA public key. A key-IV pair is generated, encrypted with RSA, and uploaded to the distant approot folder. This pair is used for encrypting and decrypting information.
Lastly, the malware retrieves lists of recordsdata from two folders positioned on OneDrive, E and F. A thread is began for every checklist, which downloads and decrypts the recordsdata. The recordsdata saved underneath the E folder include instructions to be executed, whereas those saved underneath the F folder include a listing of recordsdata to be uploaded. The outcomes of those operations are encrypted and saved in a 3rd OneDrive folder, D. The unique recordsdata are then deleted from OneDrive.
BingoShell: A Python backdoor abusing GitHub
We noticed the most recent specimen of the group’s exfiltration toolset in February 2024 and named it BingoShell due to the string bingo# used within the title of a GitHub pull request (PR) it creates. The analyzed pattern (SHA-256: 24E12B8B1255DF4E6619ED1A6AE1C75B17341EEF7418450E661B74B144570017) is a file named Replace.exe that makes use of a Microsoft Workplace emblem as its icon, as noticed in Determine 3. In keeping with its PE compilation timestamp, apparently it was inbuilt late January 2024.
Determine 3. BingoShell backdoor mimics Microsoft Workplace software
BingoShell is a backdoor written in Python that makes use of GitHub to regulate compromised machines. As soon as run, it makes use of a hardcoded token to entry a non-public GitHub repository. In keeping with the preliminary commit of the primary department, the repository was in all probability created on January twenty fourth, 2024. BingoShell creates a brand new department within the repository and a corresponding pull request. The backdoor reads feedback on the newly created PR to obtain instructions to execute on the compromised machine, as illustrated in Determine 4.
Determine 4. Code retrieving instructions saved in concern feedback
This demonstrates a brand new covert approach to leverage GitHub as a command and management (C&C) server, exhibiting the sophistication of the attackers, who cleaned up after themselves by closing pull requests and eradicating feedback from the repository.
Every new department created by BingoShell on the personal GitHub repository ought to signify an entry to a compromised machine. As a result of we found 25 closed pull requests (proven in Determine 5), we might infer that CeranaKeeper had entry, by way of BingoShell, to 25 compromised machines.
Determine 5. Enumerating the pull requests
Conclusion
The risk actor behind the assaults on the Thailand authorities, CeranaKeeper, appears significantly relentless, because the plethora of instruments and strategies the group makes use of retains evolving at a fast fee. The operators write and rewrite their toolset as wanted by their operations and react reasonably rapidly to maintain avoiding detection. This group’s objective is to reap as many recordsdata as doable and it develops particular parts to that finish. CeranaKeeper makes use of cloud and file-sharing providers for exfiltration and doubtless depends on the truth that visitors to those common providers would largely appear respectable and be tougher to dam when it’s recognized.
All through our analysis, we had been capable of set up robust connections between the beforehand documented and new toolsets and one frequent risk actor. The evaluate of the techniques, strategies and procedures (TTPs), code, and infrastructure discrepancies leads us to consider that monitoring CeranaKeeper and MustangPanda as two separate entities is critical. Nevertheless, each China-aligned teams may very well be sharing info and a subset of instruments in a typical curiosity or via the identical third social gathering.
The focused marketing campaign we investigated gave us insights into CeranaKeeper’s operations and future campaigns will possible reveal extra, because the group’s quest for delicate information continues.
For a extra detailed evaluation of the instruments deployed by CeranaKeeper, you’ll be able to entry the total ESET Analysis white paper right here.
For any inquiries about our analysis printed on WeLiveSecurity, please contact us at threatintel@eset.com.
ESET Analysis presents personal APT intelligence reviews and information feeds. For any inquiries about this service, go to the ESET Menace Intelligence web page.
IoCs
A complete checklist of indicators of compromise (IoCs) and samples may be present in our GitHub repository.
Information
SHA-256
Filename
Detection
Description
B25C79BA507A256C9CA12A9BD34DEF6A33F9C087578C03D083D7863C708ECA21
EACore.dll
Win32/Agent.VJO
YK0130 reverse shell.
E7B6164B6EC7B7552C93713403507B531F625A8C64D36B60D660D66E82646696
SearchApp.exe
Python/Agent.AGT
WavyExfiller.
3F81D1E70D9EE39C83B582AC3BCC1CDFE038F5DA31331CDBCD4FF1A2D15BB7C8
OneDrive.exe
Win32/Agent.VKV
OneDoor.
DAFAD19900FFF383C2790E017C958A1E92E84F7BB159A2A7136923B715A4C94F
dropbox.exe
Python/Agent.AQN
PyInstaller DropFlop.
24E12B8B1255DF4E6619ED1A6AE1C75B17341EEF7418450E661B74B144570017
Replace.exe
Python/Agent.AJJ
BingoShell.
451EE465675E674CEBE3C42ED41356AE2C972703E1DC7800A187426A6B34EFDC
oneDrive.exe
Python/Agent.AGP
WavyExfiller PixelDrain variant.
E6AB24B826C034A6D9E152673B91159201577A3A9D626776F95222F01B7C21DB
MsOcrRes.orp
Win32/Agent.AFWW
TONESHELL kind B.
6655C5686B9B0292CF5121FC6346341BB888704B421A85A15011456A9A2C192A
avk.dll
Win32/Agent.VJQ
TONESHELL variant.
B15BA83681C4D2C2716602615288B7E64A1D4A9F4805779CEBDF5E6C2399AFB5
TurboActivate.dll
Win32/Agent.AFWX
TONESHELL loader.
Community
IP
Area
Internet hosting supplier
First seen
Particulars
104.21.81[.]233 172.67.165[.]197
www.toptipvideo[.]com
CLOUDFLARENET (AS13335)
2023‑08‑14
C&C server for the YK0130 reverse shell.
103.245.165[.]237
dljmp2p[.]com inly5sf[.]com
Bangmod Enterprise administrator (AS58955)
2023‑04‑21
C&C servers for TONESHELL variants.
103.27.202[.]185
www.dl6yfsl[.]com
Bangmod Enterprise administrator (AS58955)
2023‑08‑10
C&C server for TONEINS variant.
103.27.202[.]185
www.uvfr4ep[.]com
Bangmod Enterprise administrator (AS58955)
2023‑09‑22
C&C server for TONEINS variant.
MITRE ATT&CK strategies
This desk was constructed utilizing model 15 of the MITRE ATT&CK framework.
Tactic
ID
Title
Description
Useful resource Improvement
T1583.001
Purchase Infrastructure: Domains
CeranaKeeper acquired domains for a few of its C&C servers.
T1583.003
Purchase Infrastructure: Digital Non-public Server
CeranaKeeper acquired entry to a VPS to function a C&C server.
T1587.001
Develop Capabilities: Malware
CeranaKeeper develops its personal parts.
T1585.003
Set up Accounts: Cloud Accounts
CeranaKeeper acquired cloud accounts for exfiltration functions.
Execution
T1072
Software program Deployment Instruments
CeranaKeeper abuses the ESET Distant Administration console to carry out lateral motion.
Persistence
T1547.001
Boot or Logon Autostart Execution: Registry Run Keys / Startup Folder
The YK0130 reverse shell establishes persistence by way of the registry Run key.
T1574.002
Hijack Execution Stream: DLL Aspect-Loading
Most parts come as side-loaded libraries together with the respectable program.
Protection Evasion
T1140
Deobfuscate/Decode Information or Data
Configuration recordsdata utilized by the OneDrive backdoor are encrypted.
T1036.005
Masquerading: Match Legit Title or Location
CeranaKeeper makes use of respectable library names to mix in.
Assortment
T1560.001
Archive Collected Knowledge: Archive by way of Utility
WavyExfiller makes use of WinRAR to compress collected information.
T1005
Knowledge from Native System
WavyExfiller collects information from the native drive (C:).
T1039
Knowledge from Community Shared Drive
WavyExfiller collects information from community shares.
T1074.001
Knowledge Staged: Native Knowledge Staging
Collected information is archived in a particular folder earlier than being uploaded.
Command and Management
T1071.001
Software Layer Protocol: Net Protocols
The completely different backdoors talk utilizing HTTP/S.
T1132.002
Knowledge Encoding: Non-Commonplace Encoding
The community protocol utilized by the YK0130 reverse shell employs customized, XOR-based encoding.
T1573.001
Encrypted Channel: Symmetric Cryptography
AES-128 mode CBC is utilized by the OneDrive backdoor to encrypt community communication.
T1573.002
Encrypted Channel: Uneven Cryptography
The generated key and IV for the OneDrive backdoor are encrypted by way of RSA.
T1090.001
Proxy: Inner Proxy
One of many variants of the YK0130 reverse shell implements a reverse proxy.
T1102.002
Net Service: Bidirectional Communication
OneDrive and Dropbox are used as C&C servers.
Exfiltration
T1567.002
Exfiltration Over Net Service: Exfiltration to Cloud Storage
Collected information are exfiltrated by way of cloud providers.