DragonForce Abuses Microsoft Teams to Mask Ransomware C2 Traffic
The DragonForce ransomware group exploited an unpatched SQL server vulnerability (or leveraged an initial access broker) to gain a foothold, then used Microsoft Teams' relay infrastructure to disguise command-and-control traffic as legitimate business communications — a tactic that renders traditional C2 detection nearly useless. By blending malicious traffic with trusted collaboration tools, attackers bypassed security controls that rely on domain or IP reputation. The use of DLL sideloading and Bring Your Own Vulnerable Driver (BYOVD) techniques further allowed them to neutralize endpoint defenses before deploying ransomware. This attack illustrates how trusted cloud platforms can become blind spots when organizations lack deep traffic inspection and behavioral analytics. Failing to patch internet-facing services and monitor lateral movement enabled a multi-stage compromise that could have been disrupted at several points.
Tactical Insight
Immediate actions
- Audit and patch all internet-facing SQL servers and other external services against known CVEs immediately.
- Enable detailed logging for Microsoft Teams and other collaboration platforms and route logs to your SIEM for anomaly detection.
- Block or alert on unexpected DLL sideloading patterns and kernel driver installations using endpoint detection and response (EDR) tooling.
Long-term improvements
- Implement network segmentation to isolate database servers, collaboration infrastructure, and critical business systems from one another.
- Establish a formal vulnerability management program with SLA-driven patching timelines, prioritizing internet-exposed and critical assets.
- Vet and continuously monitor all third-party access vectors, including initial access brokers, by enforcing zero-trust principles and least-privilege access.
Detection measures
- Deploy behavioral analytics to flag unusual outbound traffic patterns from collaboration tools like Microsoft Teams that deviate from baseline usage.
- Implement BYOVD-specific detection rules (e.g., monitoring for known vulnerable driver hashes) within your EDR and SIEM platforms.
- Conduct regular threat-hunting exercises focused on living-off-the-land and trusted-tool abuse techniques used by ransomware groups.