Attention, Microsoft Teams administrators!

Did you know that Microsoft Teams is introducing a new administrative control to protect your environment against malicious activities?1 In this blog post, we’ll explain how you can leverage this feature to enhance the security of your users.

The Problem

Some malicious actors have been using free trial tenants of Teams to launch phishing attacks and abuse against users2. This poses a significant threat to the security and privacy of your teams.

The Solution

Microsoft Teams has implemented a new setting that allows you to block external access (federation) with tenants that only have trial licenses. This adds an additional layer of protection for your users and prevents trial tenants from interacting with your teams.

How It Works

Default Configuration: After 30 days from implementation, access with trial tenants will be automatically blocked. If you want to continue federating with them, you’ll need to take explicit action.

PowerShell to the Rescue: You can use PowerShell to adjust the desired access level3. The new setting, -ExternalAccessWithTrialTenants, supports values of “Allowed” or «Blocked.»4 If set to “Blocked,” all external access with trial tenant users will be blocked.

Important Notes

• A “trial-only” tenant is defined as one with a Teams service plan that only has trial subscriptions (0 purchased licenses).
• Shared channels, guest access, and anonymous meetings are not affected by this configuration5.
• This feature only controls external communication with trial tenants within the same Microsoft 365 environment6. It does not impact communication between different clouds or with Skype for Business users7.
• If your tenant has specific allowed or blocked domain configurations, consider how this new setting will affect them

What You Should Do

• Review Your Settings: Check if you need to change the default value for this new configuration.
• Use PowerShell: Download or update to the latest version of PowerShell (6.4.0) and use the Set-CsTenantFederationConfiguration command to set the desired value9.
• Remember, the security of your teams is essential. Protect your Microsoft Teams environment today

Reference: Message Center https://admin.microsoft.com/?ref=MessageCenter/:/messages/MC805200