CIS.M365.2.1.5: Ensure Safe Attachments for SharePoint, OneDrive, and Microsoft Teams is Enabled

CIS Benchmark notice

This check implements a recommendation of the CIS Microsoft 365 Foundations Benchmark. The benchmark text is © Center for Internet Security, Inc. and is not reproduced here beyond the short summary below. Get the full benchmark free of charge from cisecurity.org.

ID	CIS.M365.2.1.5
Severity	Medium
Suite	CIS Microsoft 365 Foundations Benchmark
Product	Defender
Related products	SharePoint, Teams
Feature	Safe Attachments
Security area	Email and collaboration protection
Resource type	Tenant
User impact of fixing	Low
Effort to fix	Low
Benchmark	CIS Microsoft 365 Foundations Benchmark 7.0.0, 2.1.5 (L2, E5 Level 2)
Framework controls	cis-m365:2.1.5 nist-800-53-r5:SI-3 Malicious Code Protection
MITRE ATT&CK	T1080, T1204.002
Reads from	Exchange Online, Microsoft Graph, Security & Compliance PowerShell
Licence needed	ATP_ENTERPRISE

What this checks and how to fix it

2.1.5 (L2) Ensure Safe Attachments for SharePoint, OneDrive, and Microsoft Teams is Enabled

Safe Attachments for SharePoint, OneDrive, and Microsoft Teams scans these services for malicious files.

Rationale

Safe Attachments for SharePoint, OneDrive, and Microsoft Teams protect organizations from inadvertently sharing malicious files. When a malicious file is detected that file is blocked so that no one can open, copy, move, or share it until further actions are taken by the organization’s security team.

Impact

Impact associated with Safe Attachments is minimal, and equivalent to impact associated with anti-virus scanners in an environment.

Remediation action

To enable Safe Attachments for SharePoint, OneDrive, and Microsoft Teams:

1. Navigate to Microsoft 365 Defender https://security.microsoft.com
2. Under Email & collaboration select Policies & rules
3. Select Threat policies then Safe Attachments
4. Click on Global settings
5. Click to Enable Turn on Defender for Office 365 for SharePoint, OneDrive, and Microsoft Teams
6. Click to Enable Turn on Safe Documents for Office clients
7. Click to Disable Allow people to click through Protected View even if Safe Documents identified the file as malicious
8. Click Save.

PowerShell

1. Connect to Exchange Online using Connect-ExchangeOnline.
2. Run the following PowerShell command:

Set-AtpPolicyForO365 -EnableATPForSPOTeamsODB $true -EnableSafeDocs $true -AllowSafeDocsOpen $false

Related links

• Microsoft 365 Defender
• Safe Attachments for SharePoint, OneDrive, and Microsoft Teams
• CIS Microsoft 365 Foundations Benchmark v7.0.0 - Page 96

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Mito check, based on CIS Microsoft 365 Foundations Benchmark. Author: NZLostboy. Open-source licences.