HyperStack

HyperStack, also known as SilentMoo or BigBoss, is a Remote Procedure Call (RPC) backdoor malware that was first observed in 2018. It has been utilized in operations targeting European government entities and is linked to the Russian-based threat group Pensive Ursa, which has been operational since at least 2004. The malware exploits systems through suspicious downloads, emails, or websites, often without the user's knowledge, and once inside, it can steal personal information, disrupt operations, or even hold data hostage for ransom. HyperStack creates a service for persistence and communicates over RPC with other infected machines within a compromised environment. The malware exhibits several similarities with Pensive Ursa’s Carbon backdoor, such as the encryption scheme, configuration file format, and logging convention. These resemblances suggest that updates to HyperStack found in September 2020 were inspired by Turla's other malware operations, potentially as a response to remediation activity taken by the victim. In addition to HyperStack, prevention and detection alerts have been raised for other malware types in Pensive Ursa's arsenal including Capibar, Kazuar, Snake, Kopiluwak, QUIETCANARY/Tunnus, Crutch, ComRAT, Carbon, and TinyTurla. To mitigate the threat of HyperStack, alongside Carbon and Kazuar, ACTI recommends checking network logs for indicators related to these backdoors. Alerts for HyperStack execution prevention and service creation for persistence have been displayed in Cortex XDR in detect mode. As HyperStack continues to evolve and pose significant threats, ongoing vigilance, robust cybersecurity measures, and regular system checks are crucial for preventing potential breaches and minimizing damage.