Meeting chat for untrusted organizations is disabled

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What this check verifies

Microsoft 365 Teams meeting policy setting AllowExternalNonTrustedMeetingChat governs whether users can read or send chat messages in meetings hosted by untrusted organizations. This assesses the org-wide default policy to confirm external meeting chat with non-trusted tenants is blocked.

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Risk

Permitting chat in external meetings with untrusted tenants risks:

• Confidential data exposure via messages/files
• Malware delivery through links or media (e.g., GIF-based techniques)
• Social engineering enabling account compromise and lateral movement, degrading confidentiality and integrity

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Recommendation

Block chat for meetings hosted by non-trusted organizations and restrict collaboration to a vetted allowlist. Adopt defense in depth: limit content sharing, enable link/file scanning, enforce DLP, and user training. Review external trust relationships regularly per least privilege.

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Remediation

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References

• https://learn.microsoft.com/en-us/powershell/module/microsoftteams/set-csteamsmeetingpolicy?view=teams-ps
• https://office365itpros.com/2023/10/23/block-meeting-chat-untrusted/
• https://learn.microsoft.com/en-us/powershell/module/teams/set-csteamsmeetingpolicy?view=teams-ps

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Where this check fires

This check runs on every scheduled scan against your Microsoft 365 account. Findings appear at Cloud Security → Findings filterable by Check ID = teams_meeting_external_chat_disabled. To re-evaluate after a fix, hit Run now on the account’s schedule under Cloud Security → Schedules — the next scan re-checks this control and marks the finding fixed or keeps it persistent.

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