# (L2) Ensure external meeting chat is off

External meeting chat lets your users read and write chat messages in meetings that are hosted by organizations you have no trusted relationship with.

Source: https://maester.dev/docs/tests/CIS.M365.8.5.8

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<div class="test-byline"><div class="test-byline-avatars"><a class="test-byline-avatar test-byline-avatar--author" href="/contributors/jeremyfinney-lgtm" title="jeremy finney · Original author"><img src="https://github.com/JeremyFinney-lgtm.png" alt="jeremy finney" width="28" height="28" loading="lazy" decoding="async" /></a></div><div class="test-byline-meta"><span class="test-byline-text">Contributed by <a href="/contributors/jeremyfinney-lgtm">jeremy finney</a></span><a class="test-byline-link" href="/contributors">All contributors →</a></div></div>

<p class="test-part">Part of <a href="/docs/tests/cis">CIS</a> · Teams · Meetings · <a href="/docs/tests">All checks</a></p>

```powershell title="Run this check"
Invoke-Maester -TestId CIS.M365.8.5.8
```

## Overview

External meeting chat lets your users read and write chat messages in meetings that are hosted by organizations you have no trusted relationship with. Messages from untrusted senders can carry phishing links or malicious files into a meeting that your users are attending.

Turning this off keeps your users out of the chat in meetings hosted by untrusted organizations. Users can still chat in meetings hosted by your organization and by trusted organizations.

#### Remediation action

1. Sign in to the [Microsoft Teams admin center](https://admin.teams.microsoft.com).
2. Go to **Meetings** > **Meeting policies**.
3. Open the **Global (Org-wide default)** policy.
4. Under **External meeting chat**, select **Off**.
5. Select **Save**.

##### PowerShell

1. Connect to Teams PowerShell using `Connect-MicrosoftTeams`.
2. Run the following command:

```powershell
Set-CsTeamsMeetingPolicy -Identity Global -AllowExternalNonTrustedMeetingChat $false
```

#### Related links

* [Microsoft Teams admin center](https://admin.teams.microsoft.com)
* [Manage meeting policies in Microsoft Teams](https://learn.microsoft.com/microsoftteams/meeting-policies-in-teams)
* [Set-CsTeamsMeetingPolicy](https://learn.microsoft.com/powershell/module/teams/set-csteamsmeetingpolicy)
* [CIS Microsoft 365 Foundations Benchmark v7.0.0 - 8.5.8](https://www.cisecurity.org/benchmark/microsoft_365)

## Details

<details>
<summary>Every attribute of this check</summary>

| Field | Value |
| --- | --- |
| Test ID | CIS.M365.8.5.8 |
| Severity | Medium |
| Suite | CIS |
| Product | Teams |
| Feature | Meetings |
| Area | External access and sharing |
| Resource type | Tenant |
| User impact | Medium |
| Implementation cost | Low |
| MITRE ATT&CK | T1566 Phishing |
| Supports benchmark | CIS Microsoft 365 Foundations Benchmark (version 7.0.0), requirement 8.5.8 |
| Benchmark level | L2 |
| Benchmark profiles | E3 Level 2 |
| Supports controls | cis-m365:8.5.8, nist-800-53-r5:AC-3 |
| PowerShell test | [Test-MtCisTeamsExternalMeetingChat](https://github.com/maester365/maester/blob/main/tests/cis/Test.CIS.M365.8.5.8.ps1) |
| Services | Teams |

</details>

## Source

- Test: [`tests/cis/Test.CIS.M365.8.5.8.ps1`](https://github.com/maester365/maester/blob/main/tests/cis/Test.CIS.M365.8.5.8.ps1)
- Documentation: [`tests/cis/Test.CIS.M365.8.5.8.md`](https://github.com/maester365/maester/blob/main/tests/cis/Test.CIS.M365.8.5.8.md)