# yaml-language-server: $schema=../../../../schema/control.schema.json
id: CB-M365-COLLAB-027
title: Turn off meeting chat for anonymous participants
finding:
  title: Anonymous participants can read and post in Teams meeting chat
  description: Unauthenticated participants see the files and links shared in the meeting chat and can post links of their own to attendees.
status: active
profiles: [hardened]
risk:
  severity: low
assessment: manual
tags: [teams, meetings, anonymous-access, chat]

applicability:
  requires:
    - Microsoft Teams

description: |
  Meeting chat is on for everyone except anonymous participants (`MeetingChatEnabledType` =
  `EnabledExceptAnonymous`), or off (`Disabled`), in every meeting policy. Anonymous participants who
  are admitted cannot read or post chat messages.
rationale: |
  Meeting chat often carries documents, links and decisions that outlive the meeting. An anonymous
  participant has no accountable identity and can use the chat to post phishing links that look like
  part of the meeting. Removing chat for anonymous participants limits both exposure and abuse while
  keeping audio, video and screen sharing.
impact: |
  Anonymous participants (for example customers without an account) cannot use the chat, including to
  ask questions; use Q&A or invite them as guests. None known for authenticated participants.

setting:
  location: Teams admin center > Meetings > Meeting policies > Meeting engagement > Meeting chat
  default_value: On for everyone (Enabled)
  recommended_value: On for everyone but anonymous users (EnabledExceptAnonymous), or Off

audit:
  manual: |
    1. Sign in to the Microsoft Teams admin center (https://admin.teams.microsoft.com) as at least a
       Global Reader.
    2. Browse to **Meetings** > **Meeting policies** and open the **Global (Org-wide default)** policy,
       then every custom policy assigned to users.
    3. In the **Meeting engagement** section, check that **Meeting chat** is **On for everyone but
       anonymous users** or **Off**.
    4. With Microsoft Teams PowerShell (Global Reader is enough):
       `Get-CsTeamsMeetingPolicy | Select-Object Identity, MeetingChatEnabledType`.
    5. Fail if any policy returns `Enabled`.

remediation:
  manual: |
    1. In the Teams admin center, browse to **Meetings** > **Meeting policies** and open the **Global
       (Org-wide default)** policy.
    2. In the **Meeting engagement** section, set **Meeting chat** to **On for everyone but anonymous
       users** and **Save**. Role: Teams Administrator.
    3. Repeat for each custom policy, unless a documented exception applies to its users.
    4. PowerShell equivalent:
       `Set-CsTeamsMeetingPolicy -Identity Global -MeetingChatEnabledType EnabledExceptAnonymous`
       (repeat with `-Identity <policy>` for custom policies). Changes can take up to 24 hours to apply.

references:
  - title: Set-CsTeamsMeetingPolicy
    url: https://learn.microsoft.com/powershell/module/microsoftteams/set-csteamsmeetingpolicy
    publisher: Microsoft
    kind: vendor-doc
    accessed: 2026-10-24
  - title: Teams settings and policies reference
    url: https://learn.microsoft.com/microsoftteams/settings-policies-reference
    publisher: Microsoft
    kind: vendor-doc
    accessed: 2026-10-24
mappings:
  - framework: cis-m365
    framework_version: "7.0.0"
    id: "8.5.5"
    relation: equivalent
  - framework: nist-800-53r5
    framework_version: "5.1.1"
    id: AC-14
    relation: related
  - framework: nist-800-53r5
    framework_version: "5.1.1"
    id: AC-3
    relation: related
threats:
  - framework: mitre-attack
    id: T1566.002
related_controls:
  - id: CB-M365-COLLAB-023
    type: related
  - id: CB-M365-COLLAB-030
    type: related

authors:
  - name: Alice
    github: Sn0wAlice
introduced_in: 0.1.0
created: 2026-10-24
updated: 2026-10-24