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Microsoft 365 Security Baseline for SMBs: A Practical 30-Day Plan

8 min read

Most SMB security problems aren't "advanced attacks." They're basic gaps: no MFA enforcement, weak admin controls, unmanaged devices, and email policies left at defaults.

This 30-day plan is designed to be practical — meaning: it improves security without breaking daily work.

Week 1: Identity first (stop account takeovers)

Separate admin accounts

Admins should have a dedicated admin account (not their daily mailbox account).

Create break-glass accounts

At least two emergency accounts with strong credentials stored securely. Exclude them from Conditional Access only if required, and monitor sign-ins.

Enforce MFA for everyone

No permanent exceptions. If you must exclude someone, document why and set an expiry date.

Week 2: Conditional Access baseline (reduce risky sign-ins)

Start simple:

  • Require MFA for all users
  • Require compliant devices for admin access
  • Block legacy authentication where feasible
  • Restrict access from unmanaged devices (browser-only, limited download)

Week 3: Protect endpoints (Intune + Defender)

If you manage Windows devices, this is where you'll see massive risk reduction:

  • Enrollment coverage: confirm every business device is enrolled
  • Compliance policy: encryption + OS version + basic posture checks
  • Update rings: predictable updates (not "whenever")
  • Defender onboarding and tuning (license dependent)

Week 4: Email + data + recovery

  • Configure anti-phishing policies
  • Enable external sender tagging
  • Publish SPF/DKIM/DMARC for your domain
  • Review SharePoint/OneDrive sharing (guests, external links)
  • Define recovery strategy (native retention vs third-party backup)
  • Test at least one restore

The goal

By day 30 you should have:

  • MFA + Conditional Access baseline live
  • Managed devices + updates under control
  • Email protections tuned
  • A simple monitoring + incident workflow
  • A backlog of improvements (owned, prioritized, scheduled)

Want a quick assessment?

Download our checklist and book a free 30-minute review.