VenomRAT - ClientAny.exe

Executive Summary

The analyzed malware is a Remote Access Trojan (RAT) developed in C# and compiled as a 32-bit executable. It exhibits functionalities associated with the VenomRAT family. Upon execution, the malware attempts to achieve persistence by copying itself to the AppData directory with a predetermined name and ensuring execution at system startup. It does this either by creating a high-privilege scheduled task (if running with administrative rights) or by modifying the user’s registry Run key.

The malware initializes by decoding an AES-256 encrypted configuration embedded within itself. This configuration includes command-and-control (C2) information such as IPs, ports, and potentially a Pastebin URL that can serve as an external source for dynamic configuration. The integrity of the configuration is verified using RSA-based digital signature validation, ensuring the authenticity of the configuration data and its origin.

Once the configuration is loaded, the malware establishes a TLS-encrypted connection with the C2 server. The server certificate is validated against a preloaded trusted certificate, ensuring that the connection is only established with the correct attacker-controlled server. The malware also supports fallback and reconnection logic, and it can download and execute additional plugin modules as directed by the C2.

A key component of the malware is its keylogger. This component hooks into the low-level Windows keyboard API to intercept keystrokes. It records the keys pressed, associates them with the active window and process name, and periodically sends the captured data back to the C2. This data is stored temporarily on disk and removed after successful transmission.

The malware also includes routines for enumerating system information, including details about the CPU, RAM, GPU, installed applications, and running user processes. This data is sent to the attacker and can be used to tailor subsequent commands or payloads.

Several anti-analysis and anti-debugging mechanisms are employed to hinder detection and reverse engineering. The malware performs checks to determine whether it is running in a virtualized environment by querying the number of processor cache entries through WMI; a lower-than-expected number may indicate a sandbox or VM. It also checks whether the operating system is a Windows Server edition and uses this to avoid terminating in certain environments.

To further resist analysis, the malware includes a process killer loop that searches for and terminates known analysis, debugging, and monitoring tools. This includes processes like Task Manager, Process Hacker, Process Explorer, Regedit, and various Microsoft Defender components. This routine runs continuously to prevent the user or analyst from inspecting or disrupting its activity.

Overall, the malware combines classic RAT capabilities such as persistence, system enumeration, keystroke logging, and encrypted C2 communication with layered anti-analysis and anti-debugging techniques, allowing it to maintain control and evade detection on infected systems.