Cybercriminals are constantly evolving their tactics, and multi-factor authentication (MFA) alone is no longer enough to stop sophisticated phishing attacks. While traditional MFA adds an extra layer of security, attackers have found ways to bypass weaker authentication methods—such as SMS-based MFA or push notifications—using phishing kits and social engineering techniques.
Microsoft and security experts now recommend phishing-resistant MFA as the new gold standard, especially for administrators who manage critical systems. In this post, we’ll explore why this security shift is necessary, how phishing-resistant MFA protects your organization, and how to enforce it for Microsoft 365 admins.
Why Traditional MFA Is No Longer Enough
MFA significantly reduces the risk of unauthorized access, but not all MFA methods are equally secure. Attackers are using phishing-as-a-service kits, session hijacking, and MFA fatigue attacks to trick users into unknowingly providing access.
For example, MFA codes sent via SMS or email can be intercepted or spoofed. Even push notifications, once considered secure, are being exploited through tactics like MFA fatigue attacks, where attackers bombard users with approval requests until they mistakenly accept one.
To combat these threats, Microsoft now recommends that all administrator accounts use phishing-resistant MFA—authentication methods that remove passwords from the login process entirely and prevent access from phishing sites.
What Is Phishing-Resistant MFA?
Phishing-resistant MFA ensures that authentication credentials cannot be stolen, intercepted, or misused. Unlike traditional MFA methods, which rely on passwords or one-time codes, phishing-resistant MFA leverages cryptographic key pairs to verify identities.
Microsoft supports three phishing-resistant authentication methods for administrators:
FIDO2 Security Keys – Hardware keys that authenticate users without passwords.
Windows Hello for Business – Uses biometrics (facial recognition or fingerprint) for passwordless login.
Certificate-Based Authentication (CBA) – Uses digital certificates for multi-factor authentication.
These methods eliminate passwords, prevent phishing attempts, and ensure authentication happens only on trusted devices and networks.
How to Enforce Phishing-Resistant MFA for Administrators
Step 1: Plan the Deployment
Before enforcing phishing-resistant MFA, organizations must plan their deployment carefully to avoid lockouts. A break-glass administrator account should be excluded from MFA policies to ensure emergency access.
Step 2: Register for a Strong Authentication Method
Admins must register for a strong authentication method before a Conditional Access policy is enforced. Otherwise, they risk being locked out.
Step 3: Enforce Phishing-Resistant MFA Using Conditional Access
To require phishing-resistant MFA for administrators, configure a Conditional Access policy in Microsoft Entra ID
Navigate to the Microsoft Entra admin center https://entra.microsoft.com
Click expand Protection > Conditional Access select Policies.
Click New policy and define the policy name (e.g., "Require Phishing-Resistant MFA for Admins").
Under Users include Select users and groups and check Directory roles (include necessary Administrative roles).
Under Target resources include All cloud apps and do not create any exclusions.
Under Grant select Grant Access and check Require authentication strength and set Phishing-resistant MFA in the dropdown box.
Click Select.
Under Enable policy set it to Report Only until the organization is ready to enable it.
Click Create.
Start with a pilot group before enforcing the policy across all administrator accounts to identify any compatibility issues with PowerShell scripts or legacy applications.
This policy blocks weaker authentication options (such as SMS or app-based MFA) and ensures only phishing-resistant methods are used.
The Business Impact of Phishing-Resistant MFA
Requiring phishing-resistant MFA for administrators significantly reduces the risk of credential theft and account takeovers. It aligns with Microsoft’s security best practices and ensures compliance with CIS, NIST, and Zero Trust security models.
With cyber threats growing more advanced, organizations can no longer rely on outdated authentication methods. Enforcing phishing-resistant MFA secures your most sensitive accounts, keeps attackers out, and protects business operations from disruptions.
Need expert guidance? Let PlexHosted help! We specialize in setting up and securing Microsoft 365 environments, from phishing-resistant MFA to comprehensive security policies, compliance configurations, and ongoing monitoring.
Contact us today to optimize your Microsoft 365 setup, enhance security, and ensure your organization stays protected against evolving threats.
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