7.2.6 (L2) Ensure SharePoint external sharing is managed through domain whitelist/blacklists

Information

Control sharing of documents to external domains by either blocking domains or only allowing sharing with specific named domains.

Attackers will often attempt to expose sensitive information to external entities through sharing, and restricting the domains that users can share documents with will reduce that surface area.

Solution

To remediate using the UI:

- Navigate to SharePoint admin center

https://admin.microsoft.com/sharepoint

.
- Expand Policies then click Sharing
- Expand More external sharing settings and check Limit external sharing by domain
- Select Add domains to add a list of approved domains.
- Click Save at the bottom of the page.

To remediate using PowerShell:

- Connect to SharePoint Online using Connect-SPOService
- Run the following PowerShell command:

Set-SPOTenant -SharingDomainRestrictionMode AllowList -SharingAllowedDomainList "domain1.com domain2.com"

Impact:

Enabling this feature will prevent users from sharing documents with domains outside of the organization unless allowed.

See Also

https://workbench.cisecurity.org/benchmarks/17682

Item Details

Category: ACCESS CONTROL, MEDIA PROTECTION

References: 800-53|AC-3, 800-53|AC-5, 800-53|AC-6, 800-53|MP-2, CSCv7|13.4, CSCv7|14.6

Plugin: microsoft_azure

Control ID: b38f810fde9296376b09f2f7a6e6f96fbbdec1d6db9be261a0d9ca8f22c767c7