M365EXO-005: Safe Links policy
- Platform
- Entra ID / M365
- Category
- Advanced Threat Protection
- Severity
- High
- Zero Trust pillar
- Applications & Workloads (weight 2)
- Golden fixtures
- 3
- Branch coverage
- Observed: fixtures prove the verdicts they exercise
- Provenance
- baseline
What it checks
Safe Links in Microsoft Defender for Office 365 provides time-of-click URL verification to protect users from malicious links in email messages and Office documents. Attackers commonly use deferred phishing techniques where a URL is benign at delivery time but is changed to point to a malicious site after the email passes initial scanning. Without Safe Links, users clicking on these weaponized URLs after delivery are unprotected.
Recommended value
Safe Links enabled for email and Office apps; URL rewriting enabled; do not allow click-through to malicious URLs; real-time scanning enabled
Remediation
Configure a Safe Links policy that applies to all users with URL scanning enabled for email messages and Microsoft Office applications. Enable the setting to block users from clicking through to detected malicious URLs and turn on real-time URL scanning for suspicious links. Do not add broad URL exceptions to the do-not-rewrite list and review any existing exceptions to ensure they are still necessary and do not create security gaps.
Fixture-proven verdicts
Every verdict below is proven by a golden fixture in the module's gating test suite. This table derives from the last green run; it cannot be edited by hand.
| Scenario | Expected verdict |
|---|---|
| clean | PASS |
| empty | WARN |
| throttled | Not Assessed |
Framework mappings
- NIST SP 800-53
- SI-3
- CIS M365 Benchmark
- 2.1.5
- MITRE ATT&CK
- T1566.002