Description

A targeted espionage campaign has been observed using carefully tailored spear-phishing to deliver a multi-stage backdoor, ValleyRAT, to Chinese FinTech and cryptocurrency firms. Attackers send convincing résumé PDFs written in Simplified Chinese impersonating a senior engineer named Li Hanbing with plausible academic and employment history that contain a malicious .LNK shortcut. When opened, the shortcut invokes a PowerShell one-liner that reaches out to pan.tenire.com (and an associated C2 at 206.119.175.16), fetching artifacts such as keytool.exe, jli.dll, keytool-style components and a VBScript designed to establish persistence. The initial drop places files under %APPDATA%\Security and the VBScript programmatically creates a hidden daily scheduled task called “Security” which launches keytool.exe at 08:00, then removes traces by self-deleting. At runtime keytool.exe side-loads jli.dll and reads an RC4-encrypted payload embedded within its PE sections; the loader uses a fixed RC4 key (“123cba”) and scans for an 8-byte marker (1C3B7EFF1C3B7EFF) to extract and decrypt the shellcode in memory, avoiding disk writes. This staged approach lets the operator move from delivery to an in-memory implant without obvious on-disk artifacts. Once active, ValleyRAT performs broad reconnaissance enumerating CPU and user details, screen resolution, clipboard contents, network interfaces and open ports and attempts sandbox/VM detection via registry and environment checks. It probes WMI for security products, can terminate AV-related network controls, and supports plugins for screenshots, keylogging, file transfer, session management and remote commands. Its command-and-control architecture spans numerous .work domains hosted under AS133199, masquerading as job portals to improve resilience. Defenders are advised to look for DNS resolution to pan.tenire.com, unexpected scheduled tasks named “Security”, PowerShell executions using flags like -NoP -ep Bypass, and ImageLoad events for keytool.exe. Blocking the identified C2 ranges, restricting unsigned VBScript execution, and enforcing application whitelisting and monitoring for anomalous scheduled-task behavior will help mitigate similar intrusions.