Overview
Mid‑size client (~180 mailboxes) with repeated phishing incidents and shadow IT apps. Objective: stabilize risk fast without disrupting operations.
M365 Hardening in 10 Days: Phishing Risk Down 80%
Last updated: 2025-11-06
Constraints
No downtime allowed, limited MFA adoption history, multiple legacy mailflow rules, and third‑party add‑ins in Outlook.
What we changed
Identity & MFA
Enforced MFA for admins & high‑risk users, enabled number‑matching, blocked legacy auth, hardened conditional access.
Mail Security
Defender presets, safe links/attachments, disabled auto‑forwarding, refined spoofing policies, and mailbox rules audit.
Configuration Hygiene
Baseline Secure Score actions, admin role scoping, alert tuning, and removal of risky OAuth grants.
Results (measured)
↓ 80% phishing
Phishing‑labeled messages reaching inbox decreased 80% over 30 days, same seasonality.
↓ 100% macro ransomware
Blocked macro‑based payloads via policy and detonation (0 to date).
↑ +22% Secure Score
Score uplift in two weeks, with tracked evidence for audit.
Timeline
- Day 1–2: Readiness check, access, and baselines.
- Day 3–6: Identity/MFA rollout and mail security presets.
- Day 7–10: Clean‑up legacy rules, OAuth grants, and finalize evidence.
Stack & Evidence
Microsoft 365, Entra ID, Defender for Office 365. Evidence bundle: before/after settings, policy exports, and incident metrics (redacted).
Want these results?
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