Strengthening Active Directory Security: Key Lessons from a Configuration Audit

Disclaimer

This article is intended solely for educational purposes. The techniques described here should only be tested in controlled and authorized environments. Unauthorized use of these methods is illegal and unethical. Always follow legal and ethical guidelines when conducting security assessments.

Strengthening Active Directory Security: Key Lessons from a Configuration Audit

In modern IT environments, Active Directory (AD) serves as the backbone for identity and access management. However, poor configuration practices can expose the network to severe security risks, including privilege escalation, data theft, and domain compromise.

Based on insights from a comprehensive configuration audit, this article highlights the most critical vulnerabilities commonly encountered in Active Directory environments. We will also discuss best practices to mitigate these risks and enhance overall security.

1. Weaknesses in Active Directory Certificate Services (ADCS)

Keyword: ADCS Vulnerability

One of the most critical issues identified in the audit was the misconfiguration of Active Directory Certificate Services (ADCS). Improper certificate configurations can allow attackers to obtain privileged certificates, enabling them to impersonate domain administrators or compromise secure communication channels.

Potential Threats:

• Privilege Escalation: Gaining domain admin rights through forged certificates.
• Credential Theft: Using legitimate certificates to impersonate users.
• Service Compromise: Disrupting critical services by tampering with certificate policies.

Mitigation Strategies:

• Restrict Certificate Enrollment: Limit certificate issuance to authorized users only.
• Audit Certificate Templates: Regularly review and update certificate templates to prevent misuse.
• Apply Security Updates: Ensure all patches related to ADCS are up to date.
• Disable Weak Cryptography: Avoid outdated encryption algorithms such as RC4-HMAC.

2. Unprotected IPv6 Protocol

Keyword: IPv6 Security Risks

Many networks fail to properly secure IPv6 configurations, leaving them exposed to attacks like mDNS poisoning and IPv6 router advertisements. Attackers can exploit IPv6 to redirect traffic, perform Man-in-the-Middle (MitM) attacks, or manipulate DNS responses.

Common Attack Techniques:

• Rogue Router Advertisements: Misleading systems to accept malicious routes.
• DNS Poisoning via IPv6: Modifying name resolution responses to redirect users.

Mitigation Strategies:

• Disable Unused IPv6 Interfaces: If IPv6 is not required, disable it.
• Enable IPv6 Security Features: Use RA Guard and DHCPv6 Guard to filter unauthorized announcements.
• Monitor IPv6 Traffic: Continuously analyze IPv6 logs to detect anomalies.

3. Kerberoasting: Exploiting Kerberos Tickets

Keyword: Kerberoasting Attack

Kerberoasting is an attack technique that allows adversaries to extract Kerberos service tickets and crack them offline to reveal plaintext passwords. Attackers typically target service accounts with weak or rarely changed passwords.

Risks:

• Credential Compromise: Gaining control over service accounts.
• Lateral Movement: Using cracked credentials to pivot within the network.
• Domain Takeover: If the compromised account has privileged access.

Mitigation Strategies:

• Strong Password Policies: Enforce complex and long passwords for all service accounts.
• Ticket Encryption: Use AES-256 instead of older algorithms like RC4-HMAC.
• Audit SPNs (Service Principal Names): Identify and secure SPNs associated with sensitive accounts.
• Monitor Event ID 4769: Detect anomalous Kerberos ticket requests.

4. Privilege Escalation through ACL and DCSync

Keyword: DCSync Attack

Attackers can exploit misconfigured Access Control Lists (ACLs) in Active Directory to perform DCSync attacks. This technique involves leveraging privileges to synchronize domain data, allowing attackers to extract NTLM password hashes from the domain controller.

Critical Vulnerabilities:

• Excessive Permissions: Misconfigured ACLs granting GetChanges and GetChangesAllrights.
• Service Account Mismanagement: Accounts with unnecessary replication rights.

Mitigation Strategies:

• Audit ACL Configurations: Regularly review ACLs to remove excessive permissions.
• Restrict DCSync Rights: Only allow legitimate domain controller accounts to use replication functions.
• Monitor Unusual Replication Traffic: Set alerts for suspicious DCSync activities.

5. Legacy Protocols and NTLM Exposure

Keyword: NTLM Relay Attack

NTLM authentication is inherently vulnerable to relay attacks, where attackers intercept and forward authentication messages to gain unauthorized access. Leaving NTLM enabled on critical systems increases the risk of domain compromise.

Risks:

• Credential Theft: Intercepting NTLM hashes and relaying them to privileged systems.
• Service Abuse: Exploiting NTLM-based authentication for lateral movement.

Mitigation Strategies:

• Disable NTLM Wherever Possible: Use Kerberos instead.
• Implement Extended Protection for Authentication (EPA): Mitigates relay attacks by binding the authentication context to a specific channel.
• Enforce SMB Signing: Prevents tampering with SMB traffic.
• Enable NTLM Auditing: Log and analyze NTLM authentication events.

6. Insecure SMB Shares and Poor Port Security

Keyword: SMB Vulnerabilities

Misconfigured SMB shares exposing sensitive data or allowing write access to critical files can be easily exploited by attackers. Additionally, unsecured network ports facilitate unauthorized device connections and data interception.

Mitigation Strategies:

• Restrict SMB Access: Limit access to shares and use role-based access control (RBAC).
• Disable SMBv1: Use SMBv2 or SMBv3 to avoid known vulnerabilities.
• Implement Port Security: Restrict MAC addresses allowed to connect via physical ports.
• Audit Share Permissions: Regularly check for improperly configured shares.

Key Takeaways and Recommendations

To effectively defend against the vulnerabilities outlined in this article, organizations should adopt a proactive approach to security.

1. Regular Audits: Conduct periodic configuration reviews and vulnerability assessments.
2. Centralized Log Management: Use SIEM solutions to correlate and analyze security events.
3. Multi-Factor Authentication (MFA): Implement MFA for all privileged accounts.
4. Patch Management: Regularly update systems to address known vulnerabilities.
5. Threat Hunting: Continuously search for indicators of compromise (IoCs) and suspicious activities.

Conclusion

Active Directory environments are critical to enterprise security, but misconfigurations and outdated practices leave organizations vulnerable to attack. By adopting best practices in AD configuration and hardening, implementing robust monitoring solutions, and conducting regular audits, IT teams can significantly reduce the risk of exploitation and maintain a secure infrastructure.