General

This setting allows users by default to open files from external storage services in Teams. This includes services like Dropbox, Box, Facebook, Google Drive, OneDrive Personal, and so on.

Rationale

The connection with external storage services can lead to corporate information leaks and malware infection from untrusted storage. By blocking this connection, the risk will decrease as the chances of infection and data leaks are reduced.

Manual Instruction

Follow these steps to adjust the setting:

1. Go to the Microsoft Teams admin center at https://admin.teams.microsoft.com
2. Click Teams open and select Teams settings
3. Set all unauthorized storage services to Off

CIS Mapping

• CIS Item: 8.1.1 (L2) Ensure external file sharing in Teams is enabled for only approved cloud storage providers (Automated)
• Profile: E3 Level 2

More Information

1. https://learn.microsoft.com/en-us/microsoft-365/enterprise/manage-skype-for-business-online-with-microsoft-365-powershell?view=o365-worldwide