Symantec reports that DragonForce ransomware operators stayed hidden inside a major US services firm's network for up to two months by disguising their command-and-control traffic as ordinary Microsoft Teams activity. A new Go-based backdoor, Backdoor.Turn, grabs an anonymous Teams visitor token, routes through a legitimate Microsoft Teams relay server, and then tunnels to the attackers' real server, so defenders watching the network only see connections to genuine Microsoft infrastructure. It is the first known malware to abuse Teams relay servers this way. The attackers also used a custom malicious driver to disable defenses, and installed the backdoor after deploying ransomware, suggesting they kept access for a return visit or to resell.
ReliaQuest researchers say initial access broker KongTuke has shifted from web-based ClickFix and FileFix lures to Microsoft Teams social engineering, taking as little as five minutes to gain persistent access. The attacker reaches employees from one of five rotating Microsoft 365 tenants, uses Unicode whitespace tricks to make the display name look like internal IT help desk, then talks the victim through pasting a PowerShell command. That command downloads a ZIP from Dropbox containing a portable WinPython runtime and a Python-based RAT called ModeloRAT. The new ModeloRAT variant adds a five-server C2 pool with automatic failover, self-update, and randomized URL paths, and several major EDR products did not detect it.
Rapid7 disclosed an Iranian state-sponsored intrusion that disguised itself as a Chaos ransomware attack to mask the real goal: cyber-espionage. The threat actor (assessed with moderate confidence as MuddyWater, linked to Iran's Ministry of Intelligence and Security) initiated chat requests through Microsoft Teams, walked employees into screen-sharing sessions, then captured credentials and manipulated MFA prompts. Some victims were asked to type their passwords into local text files during the call. Persistence came from a custom backdoor (Game.exe) deployed alongside DWAgent, AnyDesk, and RDP. The fake ransomware note and Chaos leak-portal entry concealed the espionage.
Google's Mandiant team published a report on April 22 naming UNC6692, a previously untracked threat cluster running a high-conversion social engineering playbook against senior enterprise staff - 77% of observed targets were senior employees between March 1 and April 1, 2026. The attack opens with an email bombing burst, flooding the victim's inbox with spam to create urgency. The operator then sends a Microsoft Teams chat invite from an external account, posing as internal IT help, and offers to fix the spam problem via a link to a convincing phishing page called 'Mailbox Repair and Sync Utility v2.1.5'. The page forces Microsoft Edge via the microsoft-edge: URI scheme, harvests credentials through a fake 'Health Check' button, and downloads an AutoHotkey script from attacker-controlled AWS S3 that installs the SNOW malware family: SNOWBELT (a malicious Edge/Chromium extension disguised as 'MS Heartbeat' that holds persistence through Scheduled Tasks and a Startup-folder shortcut), SNOWGLAZE (a Python WebSocket tunneler wrapping traffic in Base64-encoded JSON), and SNOWBASIN (a Python bindshell for interactive remote control). Post-exploitation includes LSASS dumps, Pass-the-Hash lateral movement, PsExec and RDP over the SNOWGLAZE tunnel, and exfil via LimeWire.
Microsoft Threat Intelligence is warning of a surge in attacks where threat actors pose as IT or helpdesk staff in external Microsoft Teams cross-tenant chats to trick employees into granting remote access - then use legitimate tools to steal data while blending into normal IT activity. The attack chain has nine stages. First, the attacker opens an external Teams chat claiming to be internal IT addressing an account issue. They talk the target into starting a Quick Assist remote support session, giving the attacker direct control of the machine. From there they do quick recon via Command Prompt and PowerShell, drop a small payload in user-writable locations like ProgramData, and execute it through DLL side-loading using a trusted signed application (Autodesk, Adobe Reader, Windows Error Reporting, or even data loss prevention software - any binary with a valid Microsoft-trusted signature). HTTPS C2 blends into normal outbound traffic. They establish persistence via Windows Registry, then use Windows Remote Management (WinRM) to move laterally to domain controllers and high-value assets. Final stage: Rclone exfiltrates filtered data to external cloud storage. Microsoft's detection guidance is blunt - this blends into legitimate admin activity and is hard to distinguish from routine IT support.
TrustStrike Labs