DuneQuixote campaign targets Middle Eastern entities with “CR4T” malware – Source: securelist.com

Introduction

In February 2024, we discovered a new malware campaign targeting government entities in the Middle East. We dubbed it “DuneQuixote”; and our investigation uncovered over 30 DuneQuixote dropper samples actively employed in the campaign. These droppers, which exist in two versions – regular droppers and tampered installer files for a legitimate tool named “Total Commander”, carried malicious code to download an additional payload in the form of a backdoor we call “CR4T”. While we identified only two CR4T implants at the time of discovery, we strongly suspect the existence of others, which may be completely different malware.

The group behind the campaign took steps to prevent collection and analysis of its implants and implemented practical and well-designed evasion methods both in network communications and in the malware code.

Initial dropper

The initial dropper is a Windows x64 executable file, although there are also DLL versions of the malware sharing the same functionality. The malware is developed in C/C++ without utilizing the Standard Template Library (STL), and certain segments are coded in pure Assembler. All samples contain digital signatures, which are, however, invalid.

Upon execution, the malware initiates a series of decoy API calls that serve no practical purpose. These calls primarily involve string comparison functions, executed without any conditional jumps based on the comparison results.

The strings specified in these functions are snippets from Spanish poems. These vary from one sample to another, thereby altering the signature of each sample to evade detection using traditional detection methodologies. Following the execution of decoy functions, the malware proceeds to construct a structure for the necessary API calls. This structure is populated with offsets of Windows API functions, resolved utilizing several techniques.

Initially, the malware decrypts the names of essential Windows core DLLs using a straightforward XOR decryption algorithm. It employs multiple decryption functions to decode strings, where a single function might decrypt several strings. However, in our analysis, we observed samples where each string was decrypted using a dedicated function, each employing a slightly varied decryption algorithm.

Once the necessary strings have been decrypted, the malware uses a standard technique for dynamically resolving API calls to obtain their memory offsets by:

• retrieving the offset of the Process Environment Block (PEB);
• locating the export table offset of kernel32.dll;
• identifying the offset for the GetProcAddress function.

In the process of obtaining the PEB offset, the malware first decrypts the constant 0x60, which is used to locate the PEB64 structure. This approach is of particular interest because, typically, malicious samples or shellcode utilizing this technique opt for a hardcoded plain text constant value for this purpose.

Next, the malware begins to populate the previously created structure with the offsets of all required functions.

The dropper then proceeds to decrypt the C2 (Command and Control) address, employing a unique technique designed to prevent the exposure of the C2 to automated malware analysis systems. This method involves first retrieving the filename under which the dropper was executed, then concatenating this filename with one of the hardcoded strings from Spanish poems. Following this, the dropper calculates the MD5 hash of the concatenated string, which is then used as a key for decrypting the C2 string.

Following the decryption of the C2 string, the malware attempts to establish a connection with the C2 server using a specifically hardcoded ID as the user agent to download the payload. During our research of the C2 infrastructure, we found that the payload remains inaccessible for download unless the correct user agent is provided. Furthermore, it appears that the payload may only be downloaded once per victim or is only available for a brief period following the release of a malware sample into the wild, as we were unable to obtain most of the payload implants from active C2 servers.

Once the payload is downloaded into the process’s memory, the dropper performs a verification check for the “M” (0x4D in hexadecimal) magic byte at the start of the memory blob. This check likely serves to confirm that the payload has an MZ file signature, thereby indicating it is a valid executable format.

Total Commander installer dropper

The Total Commander installer dropper is created to mimic a legitimate Total Commander software installer. It is, in fact, the legitimate installer file, but with an added malicious file section (.textbss) and a modified entry point. This tampering results in invalidating the official digital signature of the Total Commander installer.

The installer dropper retains the core functionality of the initial dropper but with several key differences. Unlike the original dropper, it omits the use of Spanish poem strings and the execution of decoy functions. It also implements a series of anti-analysis measures and checks that prevent a connection to C2 resources, if any of the following conditions are true:

• a debugger is present in the system;
• known research or monitoring tools are among running processes;
• explorer.exe process has more than two instances
• any of the following processes are running:
  • “python.exe”
  • “taskmgr.exe”
  • “procmon.exe”
  • “resmon.exe”
  • “eventvwr.exe”
  • “process_hacker.exe”
• less than 8 GB RAM available;
• the position of the cursor does not change over a certain timeframe;
• disk capacity is less than 40 GB.

If any of the anti-analysis checks fail, the malware returns a value of 1. This specific return value plays a role in the decryption of the C2 server address. It triggers the removal of the first “h” from the beginning of the C2 URL (“https“), effectively changing it to “ttps“. As a result, the altered URL prevents the establishment of a connection to the C2 server.

Memory-only CR4T implant

The “CR4T” implant is designed with the primary goal of granting attackers access to a console for command line execution on the victim’s machine. Additionally, it facilitates the download, upload, and modification of files. The malware carries a PDB string in its code:

That’s why we dubbed it “CR4T”.

Upon execution by the dropper, the implant initiates a cmd.exe process in a hidden window and establishes two named pipes to enable inter-process communication. It then configures the user agent for communication with the C2 server, embedding the hardcoded value “TroubleShooter” as the user agent name for requests to the C2.

After that, the implant retrieves the computer name of the infected host as well as the username of the current user. Then it establishes a connection to the C2 server. This session provides interactive access to the command line interface of the victim’s machine via the earlier mentioned named pipes. Commands and their outputs are encoded using Base64 before being sent and decoded after receiving.

After establishing the connection, the implant remains idle, awaiting an initial command from the C2 operator to activate the required functionality. This command is represented by a one-byte value, each one mapped to a specific action on the infected system. These single character commands would likely make more sense for an English-speaking developer/operator than a Spanish-speaking one. i.e. “D” == Download, “U” == Upload (where a Spanish speaker might use “Cargar”).

During our investigation, we discovered evidence of a PowerShell file that had been created using the “T” command:

The threat actor was observed attempting to retrieve the names of all scheduled tasks on the infected machine beginning with “User_Feed_Sync“. These scheduled tasks were probably created by the Golang version of CR4T for persistence purposes.

Memory-only Golang CR4T implant

We also discovered a Golang version of the CR4T implant, which shares similar capabilities with the C version and has a similar string related to the internal naming:

This variant provides a command line console for interaction with infected machines, as well as file download and upload capabilities. It also possesses the functionality to execute commands on the victim’s machine. A notable difference of this version is its ability to create scheduled tasks using the Golang Go-ole library. This library leverages Windows Component Object Model (COM) object interfaces for interacting with the Task Scheduler service.

The malware is also capable of achieving persistence by utilizing the COM objects hijacking technique. And finally, it uses the Telegram API for C2 communications, implementing the public Golang Telegram API bindings. All the interactions are similar to the C/C++ version.

Infrastructure

The infrastructure used in this campaign appears to be located in the US at two different commercial hosters.

Victims

We discovered victims in the Middle East, as per our telemetry, as early as February 2023. Additionally, there were several uploads to a semi-public malware scanning service at a later stage, more specifically starting on December 12 2023, with more than 30 submissions of the droppers in the period up to the end of January 2024. The majority of these uploads also originated from the Middle East. Other sources we suspect to be VPN exit nodes geo-located in South Korea, Luxembourg, Japan, Canada, Netherlands and the US.

Conclusions

The “DuneQuixote” campaign targets entities in the Middle East with an interesting array of tools designed for stealth and persistence. Through the deployment of memory-only implants and droppers masquerading as legitimate software, mimicking the Total Commander installer, the attackers demonstrate above average evasion capabilities and techniques. The discovery of both C/C++ and Golang versions of the CR4T implant highlights the adaptability and resourcefulness of the threat actors behind this campaign.

Indicators of Compromise

DuneQuixote Droppers


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Domains and IPs


Commonline[.]space


g1sea23g.commonline[.]space


tg1sea23g.commonline[.]space


telemetry.commonline[.]space


e1awq1lp.commonline[.]space


mc.commonline[.]space


userfeedsync[.]com


Service.userfeedsync[.]com


telemetry.userfeedsync[.]com