The latest evolution of the notorious STRRAT malware, version 1.6, has been unveiled by Cyble Research And Intelligence Labs (CRIL) through a recent blog post. This new iteration introduces a fresh infection technique that poses a significant challenge to cybersecurity professionals and researchers. The method starts with a deceptive spam email carrying a malicious PDF attachment, designed to trick recipients into engaging with it.
Over the past years, the threat actor behind STRRAT has invested resources to develop new tactics aimed at hiding its presence and remaining undetected in targeted systems.
STRRAT version 1.6 stands out from its predecessors by incorporating two advanced string obfuscation techniques, Zelix KlassMaster (ZKM) and Allatori. These techniques are commonly used in proprietary software and applications to safeguard intellectual property but have been adopted here for malicious purposes.
These obfuscation methods complicate the malware’s analysis, making it challenging for security experts to discern its full capabilities and evade detection. The malware employs a spam email campaign masquerading as a legitimate company, and upon opening the attached PDF, a series of steps are triggered, ultimately leading to the download and execution of the disguised STRRAT payload.
To ensure persistence within the victim’s system, STRRAT version 1.6 utilizes a task scheduler entry involving “Skype,” allowing the malware to remain active even after system reboots. This updated version retains its ability to target various internet browsers and email clients, making it a potent threat for stealing sensitive information through activities like keylogging and credential pilfering.
With over 70 samples of STRRAT version 1.6 detected in the wild, it’s evident that threat actors are continuously refining their tactics and adapting their strategies to evade detection, exemplified by the integration of dual obfuscation techniques. The ongoing evolution of STRRAT underscores the determination of cybercriminals to stay ahead in the ever-changing landscape of cybersecurity.