Applying CIS COntrols to ACtive Directory

Active Directory (AD) is one of the most critical components of your organization’s IT infrastructure. It handles user identities, authentication, and access control, meaning that securing it should be a top priority. Without proper oversight, Active Directory can become a prime target for malicious actors, especially when weaknesses go undetected.

One of the most effective ways to keep your AD environment secure is through regular and thorough security auditing. The Center for Internet Security (CIS) Controls provides a set of best practices designed to help organizations improve their cybersecurity posture. In this article, we'll explore how these controls can be applied to Active Directory auditing, giving you the tools you need to safeguard your environment.

1. CIS Control 1: Inventory and Control of Hardware Assets

Active Directory doesn’t run in isolation; it interacts with a wide range of devices, domain controllers, workstations, and more. A good place to start your AD security efforts is by knowing exactly what hardware is interacting with your AD environment.

Audit Domain Controllers: Make sure you have an accurate inventory of all domain controllers, ensuring they’re all up to date with security patches. A compromised or outdated domain controller is an open door for attackers.

Control Hardware Access: Limit the devices that can connect to your AD environment. Unauthorized devices should not be allowed to join the domain. This will significantly reduce the chances of an attack from within the network.

2. CIS Control 2: Inventory and Control of Software Assets

Much like hardware, the software running in your AD environment needs to be controlled. Vulnerable or unauthorized software can become an entry point for attackers, putting your entire AD infrastructure at risk.

Audit Installed Software: Regularly check the software installed on domain controllers and other systems that interact with AD. Unapproved or outdated software should be removed to prevent exploitation.

Enforce Software Whitelisting: Implement an application whitelisting strategy. This ensures that only authorized software can run in your environment, preventing malicious programs from executing within your AD setup.

3. CIS Control 4: Controlled Use of Administrative Privileges

Administrative privileges in AD provide access to sensitive systems and data, so it’s critical to ensure these privileges are used properly and monitored frequently. Misuse or abuse of administrative rights can lead to disastrous consequences.

Audit Admin Group Memberships: Regularly audit the members of high-privilege groups like Domain Admins and Enterprise Admins. Ensure that only authorized personnel are included and remove any unnecessary accounts.

Track Admin Activity: Turn on auditing for all admin-level activities. Every change made by an administrator should be logged, so you can track who’s making what changes. This helps spot suspicious behavior and can help you react quickly in case of an incident.

Adopt Least Privilege: Always follow the principle of least privilege granting users only the minimum permissions they need to perform their jobs. Periodically review and adjust permissions to ensure they’re still appropriate.

4. CIS Control 5: Secure Configuration for Hardware and Software

A misconfigured system can be an easy target for attackers. Securely configuring your domain controllers and other AD components is a must to protect against vulnerabilities.

Harden Domain Controllers: Follow security hardening guides for domain controllers. This involves disabling unnecessary services, applying network restrictions, and enforcing secure settings across all systems that interact with AD.

Group Policy Configuration: Use Group Policy Objects (GPOs) to enforce security settings across your AD environment. Make sure GPOs are regularly audited for any unauthorized changes or lapses in security configuration.

Service Account Security: Service accounts often have elevated privileges. Make sure service accounts are secured with strong, regularly updated passwords and are audited for unnecessary permissions.

5. CIS Control 6: Maintenance, Monitoring, and Analysis of Audit Logs

Logs are your first line of defense in detecting and responding to security incidents. CIS Control 6 emphasizes the importance of maintaining, monitoring, and analyzing audit logs to help you identify malicious activities early on.

Enable Active Directory Auditing: Ensure that auditing is enabled for key events like login attempts, privilege escalations, and changes to critical AD objects. By regularly reviewing these logs, you can spot suspicious activities and respond quickly.

Use a SIEM System: If possible, integrate your AD logs with a Security Information and Event Management (SIEM) system. This allows you to centralize logging and get better insights across your entire network, improving detection and response times.

Set Up Alerts: Configure your environment to alert you when certain events occur, such as multiple failed login attempts, changes to user group memberships, or any unauthorized modifications to AD objects.

6. CIS Control 7: Email and Web Browser Protections

While this control is typically aimed at protecting users from phishing and web-based threats, it’s also crucial for AD security because many attacks begin through email or the web.

Protect User Credentials: Ensure your email systems have robust protections in place to prevent phishing attacks that could lead to compromised AD credentials. Similarly, ensure web browsers are configured with security settings that protect against threats like cross-site scripting (XSS) or drive-by downloads.

Monitor for Phishing Attacks: Set up email filters and monitoring to detect phishing attempts targeting users with administrative privileges or those who have access to sensitive AD resources.

7. CIS Control 10: Data Recovery Capability

You never know when disaster might strike—whether it's a hardware failure, a ransomware attack, or an accidental deletion of critical AD objects. Backups and a solid recovery plan are essential to ensure that your AD infrastructure can bounce back.

Back Up AD Regularly: Schedule regular backups of Active Directory, including system states, user configurations, and other critical data. Be sure to store these backups securely, and test them periodically to make sure they can be restored when needed.

Test Recovery Procedures: Don’t just back up AD also test your recovery plan. Regularly verify that you can restore AD in a timely manner without any data loss or issues.

8. CIS Control 16: Account Monitoring and Control

Monitoring user accounts is an essential part of AD security. You should track who has access to what and ensure that there are no unauthorized accounts or access levels.

Account Lockout Policies: Implement account lockout policies to limit the effectiveness of brute-force attacks. Review failed login attempts regularly to spot attack patterns early.

Review User Accounts: Periodically audit all AD user accounts, especially privileged ones, to ensure they still require access. Disable or remove any accounts that are no longer needed to reduce the risk of unauthorized access.

Conclusion

Active Directory security is crucial for the overall health of your organization's IT infrastructure. By leveraging the best practices outlined in the CIS Controls, you can improve the security posture of your AD environment, ensuring that it remains protected against both internal and external threats. Regular auditing, monitoring, and configuring AD according to these controls will help minimize vulnerabilities, enhance compliance, and ensure a faster response to potential incidents.