(L2) Ensure external meeting chat is off

Contributed by jeremy finneyAll contributors →

Part of CIS · Teams · Meetings · All checks

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.
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:

Set-CsTeamsMeetingPolicy -Identity Global -AllowExternalNonTrustedMeetingChat $false

Related links

• Microsoft Teams admin center
• Manage meeting policies in Microsoft Teams
• Set-CsTeamsMeetingPolicy
• CIS Microsoft 365 Foundations Benchmark v7.0.0 - 8.5.8

Details

Every attribute of this check

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
Services	Teams

Source

• Test: tests/cis/Test.CIS.M365.8.5.8.ps1
• Documentation: tests/cis/Test.CIS.M365.8.5.8.md