🔴 ClingSTUN Linux Backdoor Abuses Public STUN Infrastructure

FortiGuard Labs researchers spotted a Linux malware family they call ClingSTUN, and the name gives away its trick immediately. Instead of relying on a dedicated command server, the malicious code leans on STUN, the protocol that helps devices behind a router figure out their real public IP address. Video calling apps use it constantly, which means ClingSTUN’s network traffic hides inside something that already looks completely normal.

“ClingSTUN functions as a back-connect proxy backdoor, turning infected systems into remotely controlled proxy nodes. It abuses public STUN (Session Traversal Utilities for NAT) infrastructure to discover externally mapped IP addresses and ports, maintain NAT bindings, and improve connectivity between compromised hosts and remote operators.” reads the report published by Fortinet. “Because many of the STUN servers it contacts are legitimate public services, the resulting traffic easily blends with normal VoIP and WebRTC communications.”