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Ransomware & Malware BleepingComputer 4 weeks ago

Microsoft Teams will let admins block custom file extensions

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CyberNew Threat Research Desk
• Original Reporting: BleepingComputer
CyberNew Threat Intel Assessment
Assessed Severity: MEDIUM
Impacted Surface
Enterprise Perimeter & Network Defense
Intelligence Sector
Ransomware & Malware

Analyst Takeaway

"Microsoft Teams will soon let administrators tweak the list of file extensions commonly associated with malware and security threats to meet their company's security requirements. This will come as an update to Weaponizable File Protection, a built-in Teams messaging safety feature that scans conversations and blocks chat or channel messages with dangerous, high-risk file attachments. As detailed..."

Recommended Defense & Mitigation

  • Threat Monitoring: Ingest published IOCs into SIEM/EDR detection rules for continuous telemetry monitoring.
  • Security Awareness: Alert staff and maintain baseline endpoint hardening across endpoints.
Curated & Verified by CyberNew Threat Intelligence Desk Standard Defense Framework (NIST / MITRE ATT&CK)

Microsoft Teams

Microsoft Teams will soon let administrators tweak the list of file extensions commonly associated with malware and security threats to meet their company's security requirements.

This will come as an update to Weaponizable File Protection, a built-in Teams messaging safety feature that scans conversations and blocks chat or channel messages with dangerous, high-risk file attachments.

As detailed in a new Microsoft 365 roadmap entry, the feature is currently in development and will start rolling out in November 2026.

"Microsoft Teams is expanding admin controls for Weaponizable File Protection. Administrators will be able to customize which file types are blocked in Teams to align with their organization's security requirements or continue using the Microsoft-recommended default list," Microsoft says.

"This added flexibility helps organizations tailor file protection policies while maintaining a secure collaboration environment." 

When it reaches general availability, it will be available across Android, desktop, iOS, macOS, and web platforms for standard multi-tenant cloud environments worldwide.

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Source Verification & Original Intelligence

This threat report was reviewed by CyberNew analysts and cross-referenced with primary security disclosures from BleepingComputer.

Primary Advisory →