Demystifying Azure AD Conditional Access Policies

Introduction

In today's dynamic threat landscape, securing access to cloud applications is paramount. Traditional perimeter-based security is no longer sufficient as users access resources from various locations, devices, and networks. Azure Active Directory (Azure AD) Conditional Access policies offer a robust solution, allowing you to enforce granular access controls based on specific conditions.

This post will guide you through understanding and implementing Azure AD Conditional Access policies to significantly bolster your organization's security and compliance. We'll explore the core concepts, essential components, practical examples, and best practices to help you harness the full power of this critical Azure AD feature.

What are Conditional Access Policies?

Azure AD Conditional Access is a tool that brings together signals, makes decisions, and enforces organizational policies. It's the cloud-based policy engine in Azure AD that lives in the cloud and acts as a gatekeeper for your applications.

At its core, a Conditional Access policy is a set of IF-THEN statements. It allows you to define:

• If certain conditions are met (e.g., user signs in from an untrusted location on an unmanaged device).
• Then specific access controls are enforced (e.g., require multi-factor authentication (MFA), restrict session length, or block access).

This approach provides a dynamic and intelligent way to manage access, ensuring that only authorized users can access sensitive resources under appropriate circumstances.

Key Components

Every Conditional Access policy is composed of two main parts: Assignments and Access Controls.

Assignments

This is where you define "who" and "what" the policy applies to. Assignments determine the scope of the policy.

• Users and Groups: You can target specific users, Azure AD groups, or even roles. It's crucial to start with a pilot group before applying policies broadly.
• Cloud Apps or Actions: This specifies the applications or actions that the policy will protect. This can range from Microsoft 365 applications like Exchange Online and SharePoint Online to custom enterprise applications, or even administrative actions like managing Azure subscriptions.
• Conditions: This is the "if" part of the policy. You can define various signals to trigger the policy, such as:
  • Device Platforms: (e.g., Windows, macOS, iOS, Android).
  • Locations: Trusted (e.g., your corporate network IP ranges) or untrusted locations.
  • Client Applications: (e.g., browser, mobile apps, desktop clients).
  • Sign-in Risk: Leverages Azure AD Identity Protection to detect risky sign-ins.
  • User Risk: Leverages Azure AD Identity Protection to detect compromised user accounts.
  • Device State: Whether the device is hybrid Azure AD joined or marked as compliant.

Access Controls

These are the "then" part of the policy, defining the actions to be enforced when the specified conditions are met. Access controls can include:

• Grant Controls: These are permissions that are granted to the user. You can choose to:
  • Require multi-factor authentication (MFA): A common and highly effective control.
  • Require device to be marked as compliant: Ensures devices meet your organization's security standards.
  • Require hybrid Azure AD joined device: Verifies the device is managed by your organization.
  • Require approved client application: Limits access to applications that support modern authentication and security features.
  • Require app protection policy: For mobile devices, ensures data is protected within the app.
  • Require terms of use: Users must accept specific terms to gain access.
  You can also combine multiple grant controls, requiring all of them to be satisfied (e.g., "Require MFA" AND "Require compliant device").
• Session Controls: These controls limit the user's session after they've been authenticated. Examples include:
  • Sign-in frequency: How often the user needs to re-authenticate.
  • Persistent browser session: Allows users to stay signed in across browser sessions.
  • Filter for devices: Apply policies to specific devices.
  • Use Conditional Access App Control: Integrate with Microsoft Defender for Cloud Apps for real-time monitoring and control of cloud apps.
• Block Access: This is a straightforward control that denies access to the targeted cloud app or action when the conditions are met.

Common Use Cases

Conditional Access policies are versatile and can address a wide range of security needs. Here are some common and highly effective use cases:

• Require MFA for all users: The foundational security measure for any organization.
• Block legacy authentication: Older protocols (like POP, IMAP, SMTP) don't support MFA and are a major security risk.
• Require MFA for administrator roles: Protect your most privileged accounts with an extra layer of security.
• Grant access to specific applications only from trusted locations: Restrict access to sensitive apps from outside your corporate network.
• Require compliant devices for access to corporate resources: Ensure that only devices managed and secured by your organization can access sensitive data.
• Block access to specific applications based on sign-in risk: If a user's sign-in is deemed risky, block access to prevent potential account compromise.
• Enforce terms of use for specific applications: Ensure users acknowledge and agree to usage policies before accessing certain services.

Policy Examples

Example 1: Requiring MFA for All Users

This is a crucial policy for improving security.

• Users: All users
• Cloud Apps: All cloud apps
• Conditions: None (or you can target specific platforms if needed)
• Grant Controls: Require multi-factor authentication

Example 2: Block Legacy Authentication

Legacy authentication protocols are vulnerable and should be blocked.

• Users: All users
• Cloud Apps: All cloud apps
• Conditions:
  • Client applications: Select "Mobile apps and desktop clients" and then check "Other clients" to target legacy authentication.
• Access Controls: Block access

Example 3: Require Compliant Device for Accessing SharePoint Online

Ensure sensitive documents are accessed only from managed devices.

• Users: All users
• Cloud Apps: SharePoint Online
• Conditions:
  • Device state: Require Hybrid Azure AD joined or marked as compliant.
• Grant Controls: Require device to be marked as compliant

Best Practices

Implementing Conditional Access effectively requires a strategic approach. Here are some best practices to follow:

• Start with "Report-only" mode: Before enforcing policies, use the report-only mode to see the impact without actually blocking access. This helps you identify potential issues.
• Pilot with small groups: Test new policies with a small set of users or a specific pilot group before rolling them out company-wide.
• Use named locations: Define trusted IP address ranges for your corporate network to avoid unnecessary MFA prompts for on-premises users.
• Leverage Azure AD Identity Protection: Integrate with Identity Protection to use user and sign-in risk policies for more dynamic security.
• Keep policies simple and specific: Avoid overly complex policies that can be hard to manage and troubleshoot. Focus on specific use cases.
• Document your policies: Maintain clear documentation of all your Conditional Access policies, their purpose, and their target audience.
• Regularly review and update: Your security needs and threat landscape will evolve. Regularly review your policies to ensure they remain effective.
• Exclude break-glass accounts: Create emergency access accounts (break-glass accounts) that are excluded from most or all Conditional Access policies to prevent lockout in critical situations.

Conclusion

Azure AD Conditional Access is a powerful and indispensable tool for modern identity and access management. By intelligently combining signals like user identity, location, device health, and application, you can enforce granular access controls that adapt to the ever-changing security landscape.

Implementing a well-designed Conditional Access strategy is a significant step towards protecting your organization's valuable data and resources. Start by understanding the core components, identifying your critical applications and user scenarios, and gradually implementing policies, always prioritizing testing and review.

Embrace Conditional Access to build a more secure, resilient, and compliant digital workplace.