Microsoft 365 Security Checklist for UK Businesses
Summary: Microsoft 365 is central to many UK businesses. This checklist covers the controls that reduce account takeover and data exposure risk.
Microsoft 365 is often the centre of a UK business: email, files, Teams, SharePoint, OneDrive, calendars and identity. That makes it a high-value target. A single compromised account can expose data, enable invoice fraud, reset passwords and give attackers a route into wider systems.
Enable strong multi-factor authentication
MFA should be enabled for all users, with stronger protection for administrators and finance staff. Disable legacy authentication where possible because it can bypass modern security controls. Review MFA fatigue risks and train users not to approve prompts they did not initiate.
Review administrator roles
Too many global administrators creates unnecessary risk. Apply least privilege, use separate admin accounts, protect admin logins with strict conditional access and review privileged roles regularly.
Check mailbox rules and forwarding
Attackers often create hidden inbox rules to delete warnings, forward messages or monitor finance conversations. Review mailbox forwarding, delegation, OAuth apps and suspicious sign-ins after any suspected compromise.
Control sharing and external access
Review SharePoint and OneDrive sharing policies, public links, guest access and sensitive folders. Data exposure often happens through oversharing rather than malware.
Monitor and respond
Enable logging, review risky sign-ins and define a process for suspicious account activity. CyberXperts.ai helps UK organisations with Microsoft 365 security reviews, threat detection, data security and phishing response.
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