M365 Security
Microsoft 365 Security Checklist: 10 Checks for Businesses
Use this practical Microsoft 365 security checklist to review identity, MFA, Conditional Access, devices, email, sharing and data protection.
Microsoft 365 security starts with the basics
Microsoft 365 gives organisations a strong security platform, but the default configuration is not a complete security strategy. The most useful first step is to review the controls that protect identities, devices, data and access.
1. Review privileged accounts
Start with Global Administrators and other highly privileged roles. Remove accounts that no longer need access, use separate administrator accounts where appropriate, and review standing privilege regularly.
2. Check MFA and Conditional Access
MFA should protect users, but the important question is how it is enforced. Review Conditional Access policies for administrators, risky sign-ins, legacy authentication, unmanaged devices and sensitive applications.
3. Look for legacy authentication
Older authentication methods can bypass modern controls. Identify applications or protocols that still depend on legacy authentication and plan their removal.
4. Review Microsoft Secure Score
Secure Score is useful for identifying improvement opportunities. Treat it as a source of recommendations rather than a target to maximise blindly. Prioritise controls according to your actual business risk.
5. Review external sharing
Check SharePoint and OneDrive sharing settings, guest access and anonymous links. External collaboration should be deliberate and appropriate for the information being shared.
6. Review device compliance
Microsoft Intune and Conditional Access can work together to restrict access from devices that do not meet your security requirements. Check that compliance policies are actually being enforced.
7. Check Defender coverage
Review Microsoft Defender coverage for endpoints, identities, email and cloud resources. Gaps in onboarding can leave important parts of the environment with limited visibility.
8. Review data protection
Identify where sensitive information lives and whether Microsoft Purview sensitivity labels, DLP and auditing are appropriate for your organisation.
9. Check auditing and alerting
Make sure relevant audit data is available and that security alerts reach someone who can act on them. A control that nobody monitors is difficult to rely on.
10. Build a remediation plan
The final step is turning findings into an ordered plan. Fix high-risk identity and access issues first, then address devices, data protection and longer-term governance.
The goal is not a perfect score
A good Microsoft 365 security review should leave you with a clear understanding of your current risks, what should be fixed first and what can wait. Security improves when controls are practical, understood and maintained.
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Microsoft 365 & Azure Security
Practical Microsoft 365 and Azure security consulting for identity, cloud governance, Defender, Conditional Access and security posture improvement.