Description

ValleyRAT_S2 is a second-stage Remote Access Trojan (RAT) observed in targeted cyber-espionage campaigns, primarily affecting users and organizations across mainland China, Hong Kong, Taiwan, and Southeast Asia. The malware is deployed after an initial compromise and is designed to provide attackers with persistent, covert access for surveillance and financial data exfiltration while minimizing detection. Developed in C++, ValleyRAT_S2 is commonly distributed through trojanized software, including fake productivity tools, cracked applications, and modified legitimate programs. A core technique used is DLL side-loading, where malicious DLL files are disguised as trusted system or application libraries and loaded by legitimate executables. This method enables execution without raising immediate suspicion from traditional security controls. After execution, the malware conducts extensive system reconnaissance, gathering information on the operating system, running processes, registry entries, storage devices, and network resources. Persistence is established using Windows Task Scheduler and other native system mechanisms to ensure re-execution after system restarts. ValleyRAT_S2 also supports process injection and memory manipulation through standard Windows APIs, allowing malicious activity to blend into trusted processes. The threat posed by ValleyRAT_S2 is significant due to its stealth, persistence, and focus on sensitive financial data. Compromised systems risk long-term surveillance, credential theft, and data leakage. Organizations are advised to restrict execution of untrusted software, monitor for abnormal DLL loading behavior, audit scheduled task creation, and deploy advanced endpoint detection solutions capable of identifying injection and side-loading techniques.?