Chinese-linked threat actor UNC5174 has launched a new campaign targeting Linux and macOS systems using SNOWLIGHT malware and the VShell remote access trojan (RAT). This threat actor, connected to the Chinese government, has leveraged open-source tools for its attacks to blend in with non-state adversaries and make attribution more challenging. The malware, primarily used to gain unauthorized access, can infect both Linux and macOS, with VShell acting as a RAT to execute arbitrary commands and download or upload files to the compromised systems.
UNC5174 was previously linked to exploits in security flaws like those in Connectwise ScreenConnect and F5 BIG-IP software. Their tactics involve the use of C-based ELF downloaders like SNOWLIGHT, which fetches the GOHEAVY Golang tunneler, along with reverse shell backdoors such as GOREVERSE. These malicious tools are deployed in attacks to establish persistence on compromised systems and provide access to cybercriminals for further exploitation.
The 2024 French National Agency for the Security of Information Systems (ANSSI) report revealed that attackers were using similar techniques to weaponize known vulnerabilities in Ivanti appliances. These flaws were exploited to gain control over targeted systems and deploy rootkits for continued access. The use of open-source tools in these campaigns reflects an emerging trend where cybercriminals bypass detection by leveraging widely available tools that blend in with normal network activity. The combination of SNOWLIGHT and VShell offers a highly effective and stealthy mechanism for infiltrating organizations, making detection and mitigation more difficult.
Sysdig’s analysis in January 2025 noted that the SNOWLIGHT malware delivered the VShell RAT through a specially crafted command to the C2 server, allowing remote control over compromised systems. These attacks are marked by their use of fileless techniques, leveraging WebSockets for command-and-control communication. This makes detection more challenging for security teams, as no files are written to disk, and the malware resides solely in memory.
