The SUBTLE-PAWS PowerShell-based backdoor has emerged in a campaign targeting Ukraine, particularly aiming at Ukrainian military personnel. Conducted by threat actors, likely related to Shuckworm and tracked as STEADY#URSA, this cyber offensive utilizes advanced tactics to evade detection. The malware, delivered through compressed files, displays a shift in tactics compared to previous Shuckworm activities, showcasing increased sophistication. The SUBTLE-PAWS backdoor exhibits dynamic execution, command and control capabilities, propagation through removable media, stealth measures, and environment sensitivity, highlighting the threat actors’ efforts to operate stealthily and effectively across various Windows targets.
Throughout the attack campaign, PowerShell is prominently featured, with SUBTLE-PAWS employing techniques like storing and retrieving executable code from the Windows Registry for dynamic execution, enhancing persistence and avoiding traditional detection methods. The malware establishes communication with a remote server for command and control, using methods such as DNS queries and HTTP requests. Notably, it also spreads through removable drives, creating malicious shortcuts and potentially infecting other systems. The malware employs obfuscation techniques like Base64 and XOR encoding, along with randomization strategies, making it elusive and challenging to detect using conventional security tools.
The SUBTLE-PAWS backdoor’s level of sophistication suggests an evolution in tactics by the threat actors, emphasizing their adaptability to different system configurations and network environments. This campaign underscores the ongoing challenges posed by cyber threats, especially when they target sensitive entities like military personnel in specific regions. Security analysts and organizations need to remain vigilant, continually adapting their defenses to address the evolving techniques employed by malicious actors.
