How to Implement Multi-Factor Authentication in Microsoft 365

Multi-Factor Authentication in Microsoft 365 is one of the most effective ways to protect your users and data from cyber threats like phishing and credential theft. By requiring a second form of verification, MFA significantly reduces the risk of unauthorized access, even if a password is compromised.

What is Multi-Factor Authentication in Microsoft 365?

MFA in Microsoft 365 is a security feature that requires users to verify their identity using two or more methods:

• Something they know (e.g., password)

• Something they have (e.g., phone, security key)

• Something they are (e.g., fingerprint or facial recognition)

This extra layer of security helps prevent attackers from gaining access using stolen credentials alone.

Step-by-Step: How to Enable MFA in Microsoft 365

You can set up MFA in Microsoft 365 using either Security Defaults or Conditional Access Policies.

Option 1: Use Security Defaults (Simple Setup)

Security Defaults are the easiest way to enable MFA for all users.

1. Go to Microsoft Entra Admin Center.

2. Navigate to Overview > Properties > Manage Security Defaults.

3. Toggle Enable Security Defaults to Yes.

4. Save your changes.

Note: Security Defaults apply to all users and do not offer customization. This is great for small organizations.

Option 2: Use Conditional Access (Custom Setup)

For more control, especially in medium or large organizations, use Conditional Access.

1. Go to Microsoft Entra Admin Center.

2. Navigate to Protection > Conditional Access.

3. Click + New Policy and name it (e.g., "Require MFA for All Users").

4. Under Users, select "All users" or target specific groups.

5. Under Target resources, choose "All resources".

6. Under Access controls, select Grant access > Require multi-factor authentication.

7. Enable the policy and click Create.

Best Practices for MFA Deployment

1. Enable MFA for Admin Accounts First

According to the CIS Microsoft 365 Benchmark v4.0.0, admin accounts should be prioritized for MFA to reduce high-privilege risk.

2. Avoid Per-User MFA Settings

CIS recommends avoiding "per-user" MFA in favor of Conditional Access for better flexibility and reporting. Microsoft has documentation on migrating from per-user MFA Convert users from peruser MFA to Conditional Access based MFA

3. Use Phishing-Resistant MFA

Use Microsoft Authenticator with number matching or FIDO2 security keys for high-security scenarios.

4. Set Up Break Glass Accounts

Create two emergency accounts excluded from Conditional Access.

Implementing Multi-Factor Authentication in Microsoft 365 is a low-cost, high-impact security control that every organization should deploy. Whether you're a small business or an enterprise, enabling MFA protects your users, data, and reputation.

As a Microsoft Cloud Solution Provider and Managed Security Service Provider (MSSP), PlexHosted helps organizations of all sizes plan, configure, and enforce Multi-Factor Authentication in Microsoft 365.

Let our experts simplify the process and help you protect your users and data without the hassle.

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