Mandiant, working in partnership with SonicWall Product Security and Incident Response Team (PSIRT), has identified a suspected Chinese campaign that involves maintaining long term persistence by running malware on an unpatched SonicWall Secure Mobile Access (SMA) appliance. The malware has functionality to steal user credentials, provide shell access, and persist through firmware upgrades. Mandiant currently tracks this actor as UNC4540.
Analysis of a compromised device revealed a collection of files that give the attacker a highly privileged and available access to the appliance. The malware consists of a series of bash scripts and a single ELF binary identified as a TinyShell variant. The overall behavior of the suite of malicious bash scripts shows a detailed understanding of the appliance and is well tailored to the system to provide stability and persistence. Table 1 contains a list of the malicious files. ...read more!
