ESET researchers noticed a number of campaigns focusing on governmental establishments in Thailand, beginning in 2023. These assaults leveraged revamped variations of elements beforehand attributed by different researchers to the China-aligned superior persistent menace (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.

Based mostly on our findings, we determined to trace this exercise cluster because the work of a separate menace 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 menace 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 continuously updates its backdoor to evade detection and diversifies its strategies to assist large information exfiltration.
• CeranaKeeper abuses common, reliable cloud and file-sharing companies 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 energetic since a minimum of the start of 2022, primarily focusing on governmental entities in Asian nations resembling Thailand, Myanmar, the Philippines, Japan, and Taiwan; we imagine it’s aligned with China’s pursuits. The group’s relentless hunt for information is outstanding, with its attackers deploying a big selection of instruments aimed toward extracting as a lot data 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 elements when gathering 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 menace actor.

We introduced a few of our findings about CeranaKeeper and the compromise in Thailand on the Virus Bulletin convention on October 2^nd, 2024, and in our white paper, which you’ll learn in full right here. This month, Virus Bulletin may 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 imagine CeranaKeeper makes use of the publicly documented toolset known 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 think about using political lures and PlugX elements to be the work of MustangPanda. Regardless of some similarities of their actions (related 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 best way the 2 teams accomplish related duties.

In its operations, CeranaKeeper deploys elements generally known as TONEINS, TONESHELL, and PUBLOAD, that are distinctive to the group. The group stands out for its creativity and flexibility in its assaults, resembling utilizing revamped variations of the aforementioned elements and new instruments that abuse companies resembling Pastebin, Dropbox, OneDrive, and GitHub. We describe these instruments within the Toolset aiding large exfiltration part.

Moreover, the group left some metadata in its code that offered us with insights into its growth course of, additional solidifying our separation of the 2 teams and our attribution to CeranaKeeper. Each menace actors might depend on the identical third occasion, 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, it is a extra doubtless clarification than a single menace 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 reliable Avast driver and a customized utility 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 realize area admin privileges. This enabled CeranaKeeper to maneuver to the subsequent part of its operation and obtain the ultimate aim: large information harvesting.

Toolset aiding large exfiltration

The primary of a collection of unknown elements we found in June 2023 is WavyExfiller, a Python bundle bundled into an executable utilizing PyInstaller and a direct Python implementation of the exfiltration technique described by Unit 42. We named this element WavyExfiller because of the .wav extension of a neighborhood file that comprises 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 important features: 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 beneath the title oneDrive.exe. Regardless of its title, this model makes use of the file-sharing service PixelDrain to exfiltrate the archived recordsdata. Identical to SearchApp.exe talked about above, this variant checks the C drive, which generally comprises the working system, put in applications, 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 related exterior storage gadgets like USBs and onerous drives, networked drives in an workplace atmosphere, or digital drives created by particular software program. This reveals that CeranaKeeper stepped up its stage of greediness and tried reaching different potential or identified sources of data. Nevertheless, it’s unclear whether or not the exfiltration operation was profitable, as checking uploaded recordsdata on PixelDrain will not be doable by way of the uncovered API.

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. It appears that evidently CeranaKeeper created it primarily based on a publicly accessible challenge known as Dropflop, which is a reverse shell with add and obtain capabilities. The compiled Python file known as dropboxflop.pyc. The backdoor retrieves an encrypted Dropbox token and is dependent upon recordsdata current within the distant Dropbox repository to execute instructions on the machine. It creates a singular folder domestically and generates a “heartbeat” by updating the distant file known 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 applied: 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 reliable executable from Microsoft, as proven within the properties view in Determine 2.

OneDoor behaves in a similar way 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 comprises a URL, which the malware makes use of in an HTTP GET request. The response comprises a OneDrive token, which is utilized in subsequent requests to Microsoft OneDrive.

OneDoor additionally retrieves the ID of a folder known as approot, which is used to retailer utility 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 comprises 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 beneath the E folder include instructions to be executed, whereas those saved beneath 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 brand as its icon, as noticed in Determine 3. In keeping with its PE compilation timestamp, apparently it was inbuilt late January 2024.

BingoShell is a backdoor written in Python that makes use of GitHub to manage compromised machines. As soon as run, it makes use of a hardcoded token to entry a personal GitHub repository. In keeping with the preliminary commit of the principle department, the repository was most likely 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. 

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 may infer that CeranaKeeper had entry, by way of BingoShell, to 25 compromised machines.

Conclusion

The menace actor behind the assaults on the Thailand authorities, CeranaKeeper, appears notably relentless, because the plethora of instruments and strategies the group makes use of retains evolving at a fast charge. The operators write and rewrite their toolset as wanted by their operations and react somewhat shortly to maintain avoiding detection. This group’s aim is to reap as many recordsdata as doable and it develops particular elements to that finish. CeranaKeeper makes use of cloud and file-sharing companies for exfiltration and doubtless depends on the truth that visitors to those common companies would largely appear reliable and be tougher to dam when it’s recognized.

All through our analysis, we had been capable of set up sturdy connections between the beforehand documented and new toolsets and one widespread menace actor. The evaluation of the ways, strategies and procedures (TTPs), code, and infrastructure discrepancies leads us to imagine that monitoring CeranaKeeper and MustangPanda as two separate entities is critical. Nevertheless, each China-aligned teams could possibly be sharing data and a subset of instruments in a standard curiosity or by way of the identical third occasion.

The focused marketing campaign we investigated gave us insights into CeranaKeeper’s operations and future campaigns will doubtless reveal extra, because the group’s quest for delicate information continues.

For a extra detailed evaluation of the instruments deployed by CeranaKeeper, you possibly can entry the complete ESET Analysis white paper right here.

For any inquiries about our analysis revealed on WeLiveSecurity, please contact us at threatintel@eset.com. 

ESET Analysis gives personal APT intelligence stories and information feeds. For any inquiries about this service, go to the ESET Risk Intelligence web page.

IoCs

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

Recordsdata

Community

MITRE ATT&CK strategies

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