Microsoft Teams Gets New Admin Control to Block External Access in Trial-Only Tenants

Last month, Microsoft announced plans to introduce a new admin control to restrict external access from trial-only tenants. This new Tenant Federation setting is now generally available to help organizations safeguard against malicious activities.

What is a trial-only tenant?

A trial-only tenant refers to a Teams service plan that includes trial subscriptions. Microsoft has discovered that threat actors frequently exploit these free Teams trials to conduct phishing or abuse attacks. The new “ExternalAccessWithTrialTenants” setting adds an extra layer of protection to safeguard users from these types of cyberattacks.

With this release, Microsoft Teams will block all external access from users with trial-only subscriptions. These users will not be able to search for people and contact employees through calls, chats, or meetings. Microsoft Teams will also remove these users from existing chats.

“This new setting only controls external communication with trial-only tenants within the same Microsoft 365 cloud environment. When enforcement starts, users from trial-only tenants in public clouds will be blocked by default from external communication with users in other Microsoft 365 cloud environments and with Microsoft Skype for Business server users,” the company explained in a message on the Microsoft 365 admin center.

How this new Tenant Federation setting will affect your organization?

Microsoft states that this new Tenant Federation setting will block all external communication with trial-only tenants by default. However, IT admins can modify this setting by installing the latest PowerShell package (version 6.4.0) and running the following command: Set-CsTenantFederationConfiguration -ExternalAccessWithTrialTenants “Blocked.”

It’s important to note that this new setting does not affect Share Channels, Guest access, or Anonymous Meeting joins. Additionally, it won’t impact tenants that have blocked specific domains or have domains listed in their Block list.

Last week, Microsoft launched a new unified Teams app that allows users to switch between personal and work accounts. This new app is currently rolling out to Windows 10, Windows 11, and macOS users.