General

This check monitors whether your Teams environment allows incoming chats from external consumer Teams accounts. Consumer Teams accounts are personal Microsoft accounts that can use the free version of Microsoft Teams.

Rationale

Allowing incoming chats from consumer Teams accounts can be abused for phishing attacks and social engineering attempts.

Due to the low barrier of entry, attackers can easily use personal Microsoft accounts to send malicious links, fake requests, or other harmful content directly to your employees. Disabling this feature reduces the attack surface and helps prevent potential security incidents that could compromise your organization’s data and systems.

Attic Fix

For this check, an automated FIX is available! If Attic has write access to your Microsoft configuration, the fix will be suggested via an Attic ticket.

Manual instruction

Follow these steps to disable incoming consumer chats:

1. Navigate to the Microsoft Teams admin center
2. Go to Teams > Teams settings > External access
3. Disable "Let users communicate with users who have Teams accounts not managed by an organization (consumer accounts)"
4. Disable "Let users receive incoming calls from users who have Teams accounts not managed by an organization (consumer accounts)"
5. Save the changes

More information

1. Manage external access in Microsoft Teams
2. Teams security guide