Ensure the organization cannot communicate with accounts in trial Teams tenants

MediumLevel 1Manual reviewm365

Description

This setting controls the organization's external access with Teams "trial-only" tenants. These are tenants that don't have any purchased seats. When set to Blocked, users from these trial-only tenants aren't able to search and contact your users via chats, Teams calls, and meetings (using the users' authenticated identities) and your users aren't able to reach users in these trial-only tenants. Users from the trial-only tenant are also removed from existing chats. The recommended state for People in my organization can communicate with accounts in trial Teams tenant is Off. Microsoft introduced this setting as Off by default on July 29, 2024 in order to block attack vectors being exploited by threat actors who have abused trial tenants. Enforcing the default ensures the setting is not reenabled for any reason. Allowing users to communicate with unmanaged Teams users presents a potent...

How it is checked

Audit method: Manual review

This recommendation cannot be checked automatically. A scan lists it with these instructions when you pass --include-manual.

To audit using the UI: 1. Navigate to Microsoft Teams admin center https://admin.teams.microsoft.com/. 2. Expand External collaboration and select External access. 3. Select the Organization settings tab. 4. Verify that People in my organization can communicate with accounts in trial Teams tenant is set to Off. To audit using PowerShell: 1. Connect to Teams PowerShell using Connect-MicrosoftTeams 2. Run the following command: Get-CsTenantFederationConfiguration Verify that ExternalAccessWithTrialTenants is set to Blocked.

How it is fixed

Fix method: Guidance or infrastructure patch

To remediate using the UI: 1. Navigate to Microsoft Teams admin center https://admin.teams.microsoft.com/. 2. Expand External collaboration and select External access. 3. Select the Organization settings tab. 4. Set People in my organization can communicate with accounts in trial Teams tenant to Off. To remediate using PowerShell: 1. Connect to Teams PowerShell using Connect-MicrosoftTeams 2. Run the following command: Set-CsTenantFederationConfiguration -ExternalAccessWithTrialTenants "Blocked"

Properties

Operating systems: Any
Tags: m365saas
Reference: CIS Microsoft 365 Foundations Benchmark v7.0.0 - 8.2.4 Ensure the organization cannot communicate with accounts in trial Teams tenants