Azure AD Conditional Access Policies

Introduction

In today's dynamic cloud landscape, securing access to your organization's resources is paramount. Azure Active Directory (Azure AD) Conditional Access provides a powerful, policy-driven approach to ensure that only authenticated and authorized users can access your applications and data, under specific conditions. This blog post delves into the core concepts, common use cases, and best practices for implementing effective Conditional Access policies.

What are Conditional Access Policies?

Azure AD Conditional Access is a cloud-based identity and access management service that acts as a gatekeeper for your applications and data. It allows you to define policies that grant or deny access to cloud apps based on conditions such as user identity, location, device state, application, and real-time risk detection.

Essentially, it follows an "if-then" logic:

• IF: Certain conditions are met (e.g., a user is signing in from an untrusted location).
• THEN: Specific controls are enforced (e.g., multi-factor authentication is required, or access is blocked).

Key Components of a Conditional Access Policy

Each Conditional Access policy is built around two primary sets of controls: Assignments and Access Controls.

Assignments

Assignments define who and what the policy applies to. This includes:

• Users and groups: You can target specific users, groups, or roles. You can also exclude users or groups to create exceptions.
• Cloud apps or actions: Policies can be applied to all cloud apps, selected apps (like Microsoft 365, Azure portal, or custom applications), or specific user actions (like registering security information).
• Conditions: This is where the dynamic nature of Conditional Access shines. You can define conditions like:
  • Sign-in risk: Based on Azure AD Identity Protection's risk detection.
  • User risk: Based on Azure AD Identity Protection's risk detection for users.
  • Device platforms: Windows, macOS, iOS, Android, etc.
  • Locations: Trusted locations (e.g., your corporate network) or specific countries.
  • Client applications: Browser, mobile apps, desktop clients.
  • Device state: Whether the device is Hybrid Azure AD joined, marked as compliant by Intune, or managed.

Access Controls

Access Controls define what happens when the conditions in the policy are met. You can choose from:

• Grant: This control allows you to grant access, but you can also enforce additional requirements.
  • Require multi-factor authentication (MFA): A common and highly effective control.
  • Require device to be marked as compliant: Ensures access is from a managed and healthy device.
  • Require Hybrid Azure AD joined device: Ensures access from devices managed by your organization's on-premises AD and Azure AD.
  • Require approved client application: For mobile and desktop applications.
  • Require app protection policy: For mobile applications.
  • Require password change: For users identified as at risk.
  You can also require multiple controls to be satisfied (e.g., require MFA AND require a compliant device).
• Session: These controls can limit sessions for specific applications.
  • Use Conditional Access App Control: Integrates with Microsoft Defender for Cloud Apps to provide real-time monitoring and control.
  • Sign-in frequency: How often users need to re-authenticate.
  • Persistent browser session: Allows users to stay signed in after closing and reopening their browser.
• Block access: This is the most restrictive control, simply denying access when conditions are met.

Visual representation of a Conditional Access policy.

Common Scenarios and How to Implement Them

Let's explore some practical scenarios where Conditional Access can significantly boost your security posture.

1. Blocking Legacy Authentication

Legacy authentication protocols (like POP, IMAP, SMTP, older Office clients) do not support MFA, making them a prime target for credential stuffing attacks. Blocking them is a critical security step.

• Assignments:
  • Users: All users
  • Cloud apps: All cloud apps
  • Conditions: Client applications -> Configure -> Yes -> Select "Mobile apps and desktop clients" -> Done. Enable "Block legacy authentication".
• Access Controls: Block access.

Ensure users are updated to modern authentication clients before implementing this.

2. Requiring MFA for Risky Sign-ins

Protect your environment from compromised credentials by enforcing MFA when Azure AD detects a risky sign-in.

• Assignments:
  • Users: All users
  • Cloud apps: All cloud apps
  • Conditions: Sign-in risk -> Medium and High.
• Access Controls:
  • Grant -> Require multi-factor authentication.

3. Granting Access from Trusted Locations

Allow unrestricted access for users connecting from your corporate network while requiring additional controls from external locations.

• Assignments:
  • Users: All users
  • Cloud apps: All cloud apps
  • Conditions: Locations -> Include -> Any location. Exclude -> Trusted locations (configure your corporate IP ranges).
• Access Controls: Grant access.

You would then create a *separate* policy for "Any location" to enforce MFA or other controls for external access.

4. Enforcing Compliant Devices

Ensure that access to sensitive applications is only granted from devices that meet your organization's security and compliance standards (e.g., managed by Intune, has disk encryption, is healthy).

• Assignments:
  • Users: All users
  • Cloud apps: Select specific sensitive apps (e.g., Azure portal, SharePoint Online).
  • Conditions: Device state -> Require Azure AD joined or Hybrid Azure AD joined.
• Access Controls:
  • Grant -> Require device to be marked as compliant.

Best Practices for Conditional Access

• Start with a "report-only" mode: Before enforcing policies, use the report-only mode to understand the potential impact without disrupting users.
• Target specific apps first: Begin by applying policies to less critical apps, then gradually expand to more sensitive ones.
• Grant access with required controls: Favor "Grant" access with specific controls (like MFA, compliant device) over outright "Block access" where possible, unless it's for highly sensitive scenarios or known threats (like legacy auth).
• Exclude emergency access accounts: Always have a few break-glass accounts that are exempt from most policies to prevent accidental lockouts.
• Regularly review policies: Security needs evolve, so periodically audit and update your Conditional Access policies.
• Integrate with Identity Protection: Leverage Azure AD Identity Protection for risk-based policies to automatically respond to suspicious sign-ins.
• Document your policies: Maintain clear documentation of your policies, their purpose, and their configurations.

Conclusion

Azure AD Conditional Access is a cornerstone of modern cloud security. By understanding its components and implementing well-defined policies, you can significantly enhance the security of your digital assets, protect against a wide range of threats, and ensure a more secure and productive experience for your users. Start planning and deploying your Conditional Access strategies today to build a resilient and secure cloud environment.