6.1 Ensure SharePoint external sharing is managed through domain whitelist/blacklists

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Information

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

Rationale:

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.

Impact:

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

NOTE: Nessus has provided the target output to assist in reviewing the benchmark to ensure target compliance.

Solution

To configure document sharing restrictions:

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 configure document sharing restrictions using PowerShell:

Connect to SharePoint Online using Connect-SPOService.

Run the following PowerShell command:

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

Default Value:

Limit external sharing by domain is not checked

See Also

https://workbench.cisecurity.org/benchmarks/10751