Microsoft 365 Business Premium Security Baseline
For a current example of why layered mail controls matter, see ASCII Smuggling Phishing: What Microsoft 365 Defenders Need to Know.
For a current example of why layered mail controls matter, see ASCII Smuggling Phishing: What Microsoft 365 Defenders Need to Know.
What should a Business Premium security baseline accomplish?
A baseline is the minimum set of deliberately configured controls an organization expects across identities, devices, email, applications, and data. It should reduce common attack paths while remaining supportable for the business.
Microsoft 365 Business Premium combines Microsoft Entra ID P1, Intune, Defender for Business, Defender for Office 365 Plan 1, and Microsoft Purview capabilities. Together, these can establish a meaningful security program when configured as a system rather than isolated products.
Identity and authentication
Identity is the first control plane to harden. Require MFA through Conditional Access, block legacy authentication, move users toward phishing-resistant methods such as passkeys, use device and authentication-strength signals where appropriate, and maintain tested emergency-access accounts.
Business Premium includes Entra ID P1 and supports Conditional Access. Advanced P2 capabilities require additional licensing. Related: Microsoft Entra Passkeys & SMS/Voice MFA Retirement.
Privileged and administrator access
Minimize Global Administrator assignments, use dedicated administrative identities where appropriate, require strong MFA, review role membership, and avoid using privileged identities for routine email and browsing. Identify where additional identity-governance licensing would materially reduce risk rather than assuming every premium feature is required.
Email and collaboration protection
- Review anti-phishing, impersonation, anti-spam, and anti-malware policies.
- Configure Safe Links and Safe Attachments appropriately.
- Protect high-value users and domains against impersonation.
- Publish and maintain SPF, DKIM, and DMARC.
- Review mailbox forwarding, suspicious inbox rules, and external auto-forwarding.
For a current example of why layered mail controls matter, see ASCII Smuggling Phishing: What Microsoft 365 Defenders Need to Know.
Device management with Intune
- Enroll supported corporate devices.
- Deploy security configuration and compliance policies.
- Require encryption and supported operating-system versions.
- Use Conditional Access with device compliance where appropriate.
- Define BYOD application-protection or management requirements.
- Establish Windows update and feature-update policies.
Endpoint security with Defender for Business
- Confirm endpoint onboarding and sensor health.
- Configure antivirus and cloud-delivered protection.
- Review attack surface reduction rules and deploy them in a controlled manner.
- Enable firewall, web, and ransomware protections appropriate to the environment.
- Establish vulnerability-remediation ownership and alert-investigation procedures.
Data protection and Microsoft Purview
Start with data that would cause meaningful harm if disclosed. Define a small sensitivity-label taxonomy, identify priority information types, apply appropriate protection, use available DLP capabilities for high-value scenarios, and document ownership and exceptions before broad enforcement.
Logging, alerting, and operational visibility
Define who owns Defender alerts, identity events, device-health failures, risky sharing, and administrative changes. Confirm audit data is available for investigation and establish escalation paths before an incident occurs.
Use Microsoft Secure Score as input, not the finish line
Secure Score is useful for discovering opportunities and tracking posture, but it should not become a mandate to implement every recommendation. Prioritize using exploitability, business impact, effort, user impact, compensating controls, and licensing.
For a deeper explanation of this distinction, see Microsoft Secure Score vs. a Microsoft 365 Security Assessment.
Make the baseline operational
Assign ownership, document exceptions, review changes, track posture recommendations, test incident procedures, and revisit the baseline as Microsoft changes capabilities. Establish recurring posture reviews so configuration drift does not accumulate.
A practical 90-day order of operations
Days 1–30: Identity & Email
Inventory administrators and authentication methods, establish Conditional Access, improve MFA, review emergency access, and harden email.
Days 31–60: Devices & Endpoints
Complete Intune enrollment, compliance, update management, Defender onboarding, and endpoint hardening.
Days 61–90: Data & Collaboration
Establish priority labels and DLP scenarios, review external sharing and guests, and evaluate application consent.
Ongoing: Measure & Operate
Review Secure Score, alerts, exceptions, configuration drift, Microsoft changes, and remediation progress.
For a tactical control list, use the Microsoft 365 Business Premium Security Checklist.