CLFS Log Files Based Malware Family

Cybersecurity professionals have revealed data about a new malware family that uses the new Common Log File System (CLFS) for concealing second-stage malware in registry transaction files in order to avoid detection.

The virus, which was discovered by FireEye's Advanced team, was named PRIVATELOG, and its installation, STASHLOG. The threat actor's identity and motivations remain unknown.

Although the malware has not been identified in real-world assaults against customer environments or seen releasing any second-stage payloads, PRIVATELOG may still be in development, the product of research, or distributed as a component of highly targeted action.

CLFS is a Windows-based general-purpose logging subsystem that is available to kernel-mode and user-mode programmes such as database management systems, OLTP structures, messaging applications, and networking event management systems for the purpose of creating and distributing high-performance transaction logs.

PRIVATELOG and STASHLOG have features that enable malicious programs to linger on compromised computers and evade identification, such as the use of encrypted strings and data flow techniques specifically designed to complicate static analysis. PRIVATELOG, on the other hand, is disguised as an obfuscated 64-bit DLL named "prntvpt.dll." It uses a method known as DLL search order hijacking to load the dangerous libraries when they are called by a victim program, in this case, a program called "PrintNotify."

Businesses should use the YARA rules to monitor internal networks for malware and keep an eye out for predicators of compromise (IoCs) within endpoint detection and mitigation (EDR) system logs for relevant events.


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