Block File Sharing in Teams

COVID-19 has led many IT Departments scrambling to roll out some form of conference/ collaboration tool as many had to work remotely. This has affected organizations that where were not agile or cloud agnostic by not adopting to modern workplace earlier on.

Microsoft Teams runs on SharePoint Online, OneDrive in its core, organizations running on-premises compliance/DLP solutions will find it hard to put in controls for data in the cloud, not being an early adopter, and having to enable collaboration tools such as Microsoft Teams is a daunting task when you want to protect the organizational data from going walkabouts. If your organization is one of those, which is like a cat on the wall – how do we do it?

Block File sharing in Teams by:

1. Not assigning a SharePoint Online license for End-users

2. Not creating a Teams or Channels, if you do….

3. Create Teams for your organization but remove the Teams members from having EDIT permission on the Teams SharePoint Site.

4. Additionally if the tenant has Microsoft Cloud App Security enabled – create a session based conditional policy, which blocks upload and download of files in Teams and SharePoint Online.

SharePoint Online License – by not assigning this you deprive the end users from accessing OneDrive for business, which is primary storage for file sharing when it comes to 1-1 and group chats.

Creating a Team – when a team is created with members, this creates a SharePoint online site, which by default allows members to have edit permission on the site. By removing the EDIT permission from the Team site leaves members with only read permission leaving only the owner of the Team/SharePoint site full permission, no just do not assign or delegate the owner permission to a regular user.

Microsoft Cloud App Security – is a Microsoft CASB solution (Cloud Access Security Broker) acts as a reverse proxy. A session based conditional policy can be configured to prevent file uploads/downloads in Teams/Sharepoint site, caveat this only works when accessing them via Web but not through desktop client, hence the above point – remove EDIT permission for Team members. MCAS gives you an insight and alert when someone does indeed try to upload a file as it will block and alert the admin.

Now that you have control of filesharing and enabled Microsoft Teams, start strategic roll out of cloud solutions for DLP, Information protection and governance, classification – all of this is available via Microsoft 365 through Azure Information Protection, DLP, Azure and Defender ATP which can scan and classify your organization data automatically based on data sensitivity you can control.