(L1) Ensure external content sharing is restricted

Contributed by jeremy finneyAll contributors →

Part of CIS · SharePoint · External sharing · All checks

Run this check

Invoke-Maester -TestId CIS.M365.7.2.3

Overview

External content sharing in SharePoint Online decides who outside the organization can receive files and sites. If sharing is open to anyone, a link can be forwarded to people who are not known to the tenant, and content can leave the organization without an account check.

Restricting sharing to new and existing guests, existing guests only, or turning external sharing off, means that only people who sign in with a guest account in your directory can receive shared content. Anyone links stop working, and users keep working with their guests.

In commercial tenants, Microsoft Entra B2B integration is already enabled for new external sharing and cannot be disabled. This changes how external users are invited, not the SharePoint sharing level checked here. This test does not verify the guest’s authentication method or whether a matching guest account exists.

Remediation action

1. Sign in to the SharePoint admin center.
2. Go to Policies > Sharing.
3. Under External sharing, move the slider to New and existing guests or Existing guests, or to Only people in your organization to turn external sharing off.
4. Select Save.

To apply the setting with PowerShell, connect with Connect-PnPOnline -Url https://<tenant>-admin.sharepoint.com -Interactive and run:

Set-PnPTenant -SharingCapability ExternalUserSharingOnly

Related links

• SharePoint admin center
• Turn external sharing on or off
• External sharing overview
• Microsoft Entra B2B integration for SharePoint and OneDrive
• CIS Microsoft 365 Foundations Benchmark v7.0.0 - 7.2.3

Details

Every attribute of this check

Field	Value
Test ID	CIS.M365.7.2.3
Severity	Medium
Suite	CIS
Product	SharePoint
Feature	External sharing
Area	External access and sharing
Resource type	Tenant
User impact	Medium
Implementation cost	Low
MITRE ATT&CK	T1213.002 Sharepoint, T1530 Data from Cloud Storage
Supports benchmark	CIS Microsoft 365 Foundations Benchmark (version 7.0.0), requirement 7.2.3
Benchmark level	L1
Benchmark profiles	E3 Level 1
Supports controls	cis-m365:7.2.3, nist-800-53-r5:AC-21
PowerShell test	Test-MtCisSpoExternalContentSharing
Services	SharePointOnline

Source

• Test: tests/cis/Test.CIS.M365.7.2.3.ps1
• Documentation: tests/cis/Test.CIS.M365.7.2.3.md