M365EXO-031: Post-delivery malware scanning enabled (MS.EXO.10.3)
- 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
SCuBA MS.EXO.10.3 requires that email scanning be capable of reviewing emails after delivery. Malware signatures update continuously, so a message benign at delivery may later be recognized as malicious. Zero-hour auto purge (ZAP) retroactively removes such messages from mailboxes, reducing the window of exposure.
Recommended value
Zero-hour auto purge (ZAP) enabled on all anti-malware policies (ZapEnabled = True)
Remediation
Enable zero-hour auto purge (ZAP) on every anti-malware policy so messages later identified as malware are removed from mailboxes after delivery. Confirm ZAP is enabled across all policies, not just the default. Where a comparable third-party solution is used, verify it provides equivalent post-delivery remediation.
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 |
| known-bad | FAIL |
| throttled | Not Assessed |
Framework mappings
- NIST SP 800-53
- SI-3
- MITRE ATT&CK
- T1566.001