Storage - Block OneDrive for Business Sync From Unmanaged Devices

 

Summary

Users can sign in to their cloud tenant account via Microsoft OneDrive, and can start syncing selected folders or the entire contents of OneDrive to a local computer. By default, this includes any computer with OneDrive already installed, whether or not it is Azure Domain Joined or Active Directory Domain joined.

Reason

Since the security of unmanaged devices cannot be verified through existing policies, brokers or endpoint protection, they may become risky. If the users are allowed to sync data to these devices, then, this will take that data out of the control of the organization which in turn increases the risk of the data either being intentionally or accidentally leaked.

Note- However, this setting is only applicable to Active Directory domains when operating in a hybrid configuration and not to Azure AD domains. If you have devices which are only Azure AD joined, then, Conditional Access policy can be used instead.

What If?

If this feature is enabled, then, it will prevent the users from using the OneDrive for Business Sync client on devices that are not joined to the domains that were defined.

How to?

To block the sync client on unmanaged devices, use the Microsoft 365 Admin Center:

1. Navigate to Microsoft 365 administration portal (https://admin.microsoft.com), click on All Admin centers and then Show All, then SharePoint.
2. Now, click Settings followed by OneDrive - Sync
3. Check the  Allow syncing only on computers joined to specific domains
4. Use the Get-ADDomain PowerShell command to obtain the GUID from each domain then add them to the box.
5. Click Save

To block the sync on unmanaged devices, you can also use SharePoint Online PowerShell:

1. Connect to SharePoint Online using Connect-SPOService
2. Now, run the following PowerShell command and provide the DomainGuids from the Get-AADomain command:

Set-SPOTenantSyncClientRestriction -Enable -DomainGuids "786548DD-877B-4760-A749-6B1EFBC1190A; 877564FF-877B-4760-A749-6B1EFBC1190A"

Note: Utilize the -BlockMacSync:$true parameter if conditional access is not being used, to ensure Macs cannot sync.

Monitor:

To verify sync settings on unmanaged devices, use the Microsoft 365 Admin Center:

1. Navigate to Microsoft 365 administration portal (https://admin.microsoft.com), click on All Admin centers and then Show All, then SharePoint.
2. Now, click Settings followed by OneDrive - Sync
3. Verify that  Allow syncing only on computers joined to specific domains is checked
4. Verify that the Active Directory domain GUIDs are listed in the box.

• Use the Get-ADDomain PowerShell command to obtain the GUID for each on-premises domain

To verify sync settings on unmanaged devices, you can also use SharePoint Online PowerShell:

1. Connect to SharePoint Online using Connect-SPOService
2. Now, run the following PowerShell command:

Get-SPOTenantSyncClientRestriction | fl TenantRestrictionEnabled, AllowedDomainList

      3. Verify TenantRestrictionEnabled is set to True and AllowedDomainList is populated and valid.