Conditional Access policies form the final leg of the prerequisite triangle. These aren’t optional — they’re how you enforce the “trust zero, verify always” principle of Zero Trust. The National Institute of Standards and Technology defines Zero Trust architecture as requiring continuous verification and explicit access grants based on all available data points. I configure policies that require device compliance, enforce multi-factor authentication for sensitive operations, and block legacy authentication entirely. The policy I typically recommend as a starting point requires hybrid-joined devices, compliant Intune status and MFA for all access to on-premises resources, while allowing seamless sign-in for fully compliant devices. This creates a virtuous cycle where security and user experience reinforce each other.
Architecture decisions: Hybrid authentication flows and Windows Hello for Business
Once your prerequisites are in place, you face critical architectural decisions that will shape your deployment for years to come. The primary decision point is whether to use Windows Hello for Business, FIDO2 security keys or phone sign-in as your primary authentication mechanism.
In my experience, Windows Hello for Business is the foundation for hybrid environments. It leverages biometric or PIN authentication on the device itself, preventing credentials from ever being transmitted across the network. When a user signs in with Windows Hello, they’re not sending a password or even a credential — they’re using a private key stored in the device’s Trusted Platform Module (TPM) to prove their identity. For hybrid-joined devices, this works seamlessly because the device can authenticate both to your on-premises domain controller (using cloud Kerberos) and to Entra ID in a single operation. This eliminates the attack surface that traditional password-based authentication creates. Organizations seeking more information on passwordless authentication approaches can review guidance from the Cybersecurity and Infrastructure Security Agency, which has published extensive recommendations on moving beyond passwords.
