Microsoft 365 security settings you should enable

8 May 2026

Microsoft 365 gives businesses a solid security foundation out of the box, but default settings are rarely enough.

Cyber attacks now target email accounts, cloud storage, employee devices, and weak passwords every day. Small businesses are especially vulnerable because attackers know many organisations never fully configure their Microsoft 365 environment.

The good news is that a few key security settings can dramatically reduce risk.

Here are the most important Microsoft 365 security settings every business should enable.

1. Turn on Multi-Factor Authentication (MFA)

If you only enable one security feature in Microsoft 365, make it MFA.

Multi-Factor Authentication requires users to verify their login with a second method, such as:

• Microsoft Authenticator app
• Text message code
• Phone notification
• Hardware security key

Even if a password is stolen, MFA can stop attackers from accessing the account.

Why it matters

Password theft is one of the most common causes of Microsoft 365 breaches. Phishing emails, reused passwords, and leaked credentials are all major risks.

MFA blocks the vast majority of account compromise attempts.

Recommended setup

• Require MFA for all users
• Prioritise admin accounts immediately
• Use the Microsoft Authenticator app instead of SMS where possible
• Disable legacy authentication protocols that bypass MFA

2. Strengthen password policies

Weak passwords still create major security problems.

Microsoft 365 includes password protection tools that help prevent users from choosing easily guessed passwords.

Recommended password settings

• Require long passwords or passphrases
• Block common passwords
• Prevent password reuse
• Enable password protection policies
• Encourage password manager use

Avoid outdated password rules

Frequent forced password changes can actually reduce security because users tend to choose weaker passwords.

Instead, focus on:

• Strong passwords
• MFA
• Monitoring suspicious sign-ins

3. Enable Conditional Access policies

Conditional Access allows you to control who can access Microsoft 365 and under what conditions.

You can create rules based on:

• User identity
• Device compliance
• Location
• Risk level
• Application access

Useful Conditional Access policies

• Block sign-ins from high-risk countries
• Require MFA outside the office
• Prevent unmanaged devices from accessing company data
• Restrict admin access to compliant devices only
• Block risky sign-ins automatically

Conditional Access is one of the most effective ways to reduce unauthorised access.

4. Use Microsoft Intune for device management

Remote and hybrid work means company data now lives on laptops, phones, and tablets everywhere.

Microsoft Intune helps businesses manage and secure those devices.

What Intune can do

• Enforce device encryption
• Require screen locks
• Ensure devices stay updated
• Separate work and personal data
• Remotely wipe lost or stolen devices
• Block non-compliant devices from accessing Microsoft 365

Why this matters

A lost laptop without encryption can become a serious data breach.

Device management helps protect company information even when employees work remotely.

5. Protect administrator accounts

Admin accounts are prime targets for attackers.

If an attacker gains global admin access, they can:

• Read company email
• Reset passwords
• Access files
• Create new accounts
• Disable security settings

Best practices for admin accounts

• Enable MFA immediately
• Use separate accounts for admin tasks
• Limit the number of global admins
• Review admin roles regularly
• Enable Privileged Identity Management (PIM) if available
• Monitor admin activity logs

Avoid using global admin accounts for normal day-to-day email and browsing.

6. Disable legacy authentication

Older authentication methods like POP, IMAP, and basic SMTP authentication are commonly targeted because they often bypass modern security protections.

Attackers frequently use password spraying attacks against these older protocols.

Recommended action

Disable legacy authentication wherever possible.

Modern authentication supports:

• MFA
• Conditional Access
• Improved monitoring
• Better security controls

This is one of the most overlooked Microsoft 365 security improvements.

7. Enable Microsoft Defender protections

Microsoft 365 includes built-in security tools through Microsoft Defender.

These tools help protect against:

• Phishing attacks
• Malware
• Malicious links
• Suspicious attachments
• Business email compromise

Important features to enable

• Safe Links
• Safe Attachments
• Anti-phishing policies
• Anti-spam protection
• User impersonation protection

Email remains the most common attack method, so securing it properly is critical.

8. Configure data loss prevention (DLP)

Data Loss Prevention policies help stop sensitive information from being shared accidentally.

This can include:

• Financial information
• Customer records
• Personal data
• Confidential business files

DLP can help by

• Detecting sensitive information
• Blocking risky sharing activity
• Warning users before sending data
• Preventing external sharing

This is especially important for businesses handling regulated or confidential information.

9. Review external sharing settings

Microsoft 365 makes collaboration easy, but unrestricted file sharing can create security risks.

Review sharing settings for:

• SharePoint
• OneDrive
• Teams

Recommended controls

• Limit anonymous sharing links
• Set expiration dates on shared links
• Restrict external sharing where unnecessary
• Monitor guest user access
• Review inactive guest accounts regularly

Many businesses unknowingly expose sensitive files through overly permissive sharing settings.

10. Monitor sign-ins and security alerts

Security settings are only part of the solution. Ongoing monitoring is equally important.

Microsoft 365 provides visibility into:

• Failed sign-in attempts
• Impossible travel activity
• Suspicious login locations
• Malware detections
• Risky users

What businesses should do

• Review alerts regularly
• Investigate unusual sign-ins
• Enable automated alerting
• Audit user activity
• Use Microsoft Secure Score for recommendations

Early detection often prevents a small issue from becoming a serious breach.

Maple's thoughts

Microsoft 365 includes powerful security tools, but many businesses never fully configure them. Enabling MFA, strengthening access controls, managing devices, and monitoring suspicious activity can significantly reduce the risk of cyber attacks. Security is not about adding unnecessary complexity. It is about putting the right protections in place before problems happen. If you are unsure whether your Microsoft 365 environment is configured securely, a security review can quickly identify gaps and prioritise improvements. Get in touch with us.