Adversaries are exploiting Microsoft Teams' default external chat functionality to conduct social engineering attacks and deliver malicious payloads. Analysis of over 400 incidents reveals threat actors consistently impersonate IT support personnel using throwaway Microsoft 365 tenants with IT-themed display names marked as "(Internal)" to bypass external-user warnings. Attacks frequently begin with email bombing followed by Teams contact offering assistance. Adversaries leverage legitimate remote monitoring tools like Quick Assist, AnyDesk, and ScreenConnect to gain hands-on-keyboard access, progressing from initial contact to payload execution in under 15 minutes. Infrastructure patterns show a shift from default onmicrosoft domains toward paid top-level domains, particularly .top domains comprising 50 percent of observed cases. The technique exploits legitimate collaboration features rather than software vulnerabilities, requiring organizations to implement allow-list policies and user training to disru...