DragonForce Hackers Abuse Microsoft Teams Relays to Hide Backdoor.Turn C2 Traffic

Symantec and Carbon Black found DragonForce-linked hackers using Backdoor.Turn, a Go RAT tunneling C2 through Microsoft Teams TURN relays via QUIC.

Broadcom's Symantec and Carbon Black documented Backdoor.Turn, a Go-based RAT associated with the DragonForce ransomware group, deployed at a major U.S. services firm where attackers remained on the network for one to two months. The backdoor obtains an anonymous Teams visitor token from Microsoft's Skype-backed identity services, uses a legitimate Microsoft TURN relay for connection setup, and runs a QUIC session to the attacker's C2 server, so defenders see only outbound traffic to legitimate Teams servers. Initial access is suspected to involve exploiting a SQL/MS-SQL vulnerability or an access broker, followed by a PowerShell-dropped ZIP, DLL side-loading, and BYOVD evasion using a Huawei driver; the RAT is injected into DbgView64.exe after DragonForce ransomware deployment for continued access. First publicly documented TURN abuse by the group, it leverages Praetorian's Ghost Calls technique and supports command execution, network scanning, LDAP/AD search, lateral movement, and browser credential theft.