Azure Active Directory (Azure AD), now rebranded as Microsoft Entra ID, is the cloud-based identity and access management service that powers organisations worldwide. From authenticating users for Microsoft 365 to managing access to a vast range of cloud services, Azure AD is at the heart of modern enterprise security. However, because it is such a critical part of an organisation’s infrastructure, it is also a prime target for attackers.
INTRODUCTION
In this detailed blog post, we will explore pentesting Azure AD, uncovering common vulnerabilities, and outlining effective techniques for testing its security. We will also share defensive strategies to bolster Azure AD security and minimise the risk of exploitation.
UNDERSTANDING AZURE AD (ENTRA ID)
Before we begin testing Azure AD, we need to understand what it is and how it fits into the larger cloud ecosystem.
Azure AD is a cloud-based directory and identity management service that supports single sign-on (SSO), multi-factor authentication (MFA), and restricted resource access. It is intended to link customers to apps from Microsoft cloud services such as Microsoft 365 and thousands of third-party apps. Azure AD enables hybrid environments by connecting on-premises Active Directory with cloud apps.
With so many enterprises relying on Azure AD, getting unauthorised access to an Azure AD environment may result in severe breaches, giving attackers access to sensitive data, corporate apps, and even control over on-premises equipment.
WHY AZURE AD IS A PRIME TARGET?
Entra ID controls access to critical systems, data, and applications. A breach can have severe consequences, such as unauthorised data access, lateral movement within networks, and even total domain control. Penetration testing simulates real-world attacks to identify:
- Misconfigurations that weaken security.
- Weak credentials or policies enabling unauthorised access.
- Hybrid identity risks introduced by Azure AD Connect or legacy protocols.
- Privileged access misuse, including overly permissive roles and administrative accounts.
By conducting penetration tests, organisations can proactively uncover and mitigate risks before attackers exploit them.
Pentesting Azure AD: Key Attack Areas
1. Reconnaissance and enumeration
The first phase of any pentesting engagement is gathering information. When it comes to Azure AD, there are several tactics to perform enumeration and gather data about the target tenant.
- Tenant discovery: Azure AD allows attackers to search for domains to identify tenant IDs. Attackers can gather tenant information by performing DNS lookups and using AutoDiscover endpoints.
- User enumeration: Attackers often begin by determining valid usernames to target in subsequent attacks. OAuth and SSO endpoints are commonly tested to identify valid accounts.
- Domain enumeration: Understanding the domain structure in Azure AD can provide attackers with crucial insights.
2. Password spraying and credential stuffing
Once valid users are identified, attackers will typically attempt to gain unauthorised access by brute-forcing or spraying credentials across multiple accounts.
- Password spraying: Unlike traditional brute-force attacks, password spraying involves using common passwords (e.g., Password123, Winter2024!) against many accounts to avoid triggering account lockouts.
- Credential stuffing: When breaches from other services are leaked (think LinkedIn or other breached sites), attackers attempt to use the same credentials on Azure AD using credential stuffing. They leverage the stolen credentials, hoping the user reused passwords across multiple platforms. Countermeasures include enabling MFA, enforcing strong password policies, and using the Identity Protection feature in Azure AD to detect risky sign-ins.
3. Exploiting conditional access policies
Conditional access is a feature of Azure AD that allows organisations to set policies governing who can access specific resources based on variables like location, device compliance, and risk levels. However, if misconfigured, these policies can create serious security risks.
- Misconfigured policies: Attackers often attempt to bypass conditional access policies. For example, overly permissive policies may allow access from any location or device, bypassing security checks. CAAPE (Conditional Access Exploitation Toolkit) can help pentesters identify weak or unrestrictive policies, such as policies that allow access from untrusted locations or devices that don’t meet the company’s compliance standards.
- Legacy authentication: Conditional access policies can block legacy authentication protocols (like IMAP, POP, and SMTP), which attackers may try to exploit. If legacy authentication is allowed, attackers can bypass more secure protocols and gain access to the system without triggering MFA. Ensure legacy protocols are disabled.
4. Privilege escalation in Azure AD
Privilege escalation is a core focus of any pentesting engagement, and Azure AD is no different. Many organisations assign excessive permissions, granting users higher roles than they need to perform their job functions.
- Exploiting misassigned roles: By exploiting misconfigured roles or gaining access to service principals, an attacker can elevate their privileges within Azure AD. Example: If a user is assigned the Global Administrator role, they can bypass MFA and gain full access to all Azure AD resources.
- Service principal abuse: In Azure AD, service principals (applications) are often assigned high-level permissions. By identifying poorly secured service principals, attackers can potentially elevate their access.
5. Token hijacking and replay attacks
Tokens play a critical role in Azure AD’s authentication process. They are used for everything from logging into Microsoft 365 to accessing APIs. Attackers frequently target these tokens, as they can be used to hijack sessions and elevate their own privileges.
- Token replay: If an attacker gains access to a valid access token, they can use it to access services without needing to authenticate again.
- Session hijacking: Attackers can hijack existing sessions if tokens are not adequately secured or rotated. Session hijacking can result from a failure to implement proper token expiration and secure cookie handling.
6. MFA Weaknesses and phishing attacks
While multi-factor authentication (MFA) is a critical layer of security for Azure AD, attackers have become increasingly adept at bypassing MFA protections.
- MFA fatigue: Attackers bombard users with MFA prompts to induce fatigue. Users may unknowingly approve an attacker’s request when they become tired of approving requests.
- Countermeasure: Implementing MFA with more advanced behavioural analytics can help to detect and mitigate MFA fatigue attacks.
- SSO phishing: Attackers may craft fake login pages that mimic legitimate Microsoft or Azure AD login portals to harvest credentials. Training users to recognise phishing attempts and enforcing MFA even for the login page can greatly reduce the risk.
Best practices for securing Entra ID
After identifying vulnerabilities, organisations should:
1. Harden authentication
- Enforce MFA for all users, including administrators.
- Disable legacy authentication protocols such as POP3, IMAP, and SMTP.
- Implement conditional access policies with strict requirements for device compliance, location, and risk-based triggers.
2. Optimise privileged identity management
- Use PIM for all privileged roles, enforcing JIT access and periodic reviews.
- Monitor and remove inactive privileged roles or accounts.
3. Strengthen hybrid identity configurations
- Regularly audit Azure AD Connect configurations and sync rules.
- Review the security of on-premises identity infrastructure to prevent hybrid exploitation.
4. Secure application permissions
- Restrict application permissions to the principle of least privilege.
- Regularly review and remove unused app registrations or permissions.
5. Monitor and respond
- Integrate Entra ID logs into a SIEM, like Microsoft Sentinel, for continuous monitoring.
- Enable Identity Protection to detect and respond to unusual login behaviours or credential compromises.
Conclusion
Microsoft Entra ID is a critical security component for organisations, and its compromise can have far-reaching consequences. Penetration testing for Entra ID provides valuable insights into vulnerabilities, allowing organisations to address risks proactively and strengthen their identity security posture.
By focusing on authentication, privileged access, hybrid identity, and application security, organisations can stay one step ahead of attackers and ensure that identity remains a stronghold, not a liability.
Secure your identities today—don’t wait for an attack to reveal your vulnerabilities.
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