This revelation follows Sophos’ recent “Pacific Rim” reports, which detail a five-year campaign involving Chinese threat actors targeting network devices at an unprecedented scale. Among the identified tools, “Pigmy Goat” stands out as a rootkit crafted to resemble legitimate Sophos product files, making it challenging to detect. This strategy is known to use stealth by masking its identity within commonly named system files to evade basic detection protocols.
“Pigmy Goat” enables threat actors to establish persistent, unauthorized access to the target’s network. Using the LD_PRELOAD environment variable, it embeds itself in the SSH daemon (sshd), allowing it to intercept and alter incoming connections.
The malware seeks specific sequences called “magic bytes” to identify backdoor sessions, which it redirects through a Unix socket, thereby concealing its presence from standard security monitoring. Once a connection is established, it communicates with command and control (C2) servers over TLS. The malware cleverly mimics Fortinet’s FortiGate certificate, blending into networks where Fortinet devices are prevalent, to avoid suspicion.
This backdoor offers threat actors multiple capabilities to monitor, control, and manipulate the network environment. Through commands from the C2, attackers can remotely open shell access, track network activity, adjust scheduled tasks, or even set up a SOCKS5 proxy, which helps them remain undetected while maintaining control over the network. These actions could allow unauthorized data access or further exploitation, posing significant threats to organizational cybersecurity.
The NCSC report aligns “Pigmy Goat” with tactics used in “Castletap” malware, which cybersecurity firm Mandiant has linked to Chinese nation-state actors. The report’s insights reinforce concerns over the evolving sophistication in state-sponsored cyber tools aimed at infiltrating critical network infrastructure worldwide.
Detection and prevention of “Pigmy Goat” are crucial to mitigating its impact. The NCSC report provides tools for identifying infection, including file hashes, YARA rules, and Snort rules, which can detect specific sequences and fake SSH handshakes associated with the malware.
Additionally, monitoring for unusual files and behaviours, such as encrypted payloads in ICMP packets or the use of ‘LD_PRELOAD’ within the sshd process, can be effective. These insights empower network defenders to recognize early signs of compromise and respond swiftly, reinforcing defences against this sophisticated threat.
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