AD CS Best Practices

Apply the principle of least privilege to all AD CS components, including certificate templates, CA configurations, and administrative access.

• Regularly review and audit access permissions for AD CS components
• Use role-based access control (RBAC) for CA administration
• Limit the number of users with administrative privileges on CA servers
• Implement Just-In-Time (JIT) and Just-Enough-Administration (JEA) for administrative tasks

Regularly audit and secure certificate templates. Disable or remove unused templates, and ensure proper access controls on sensitive templates.

• Disable or remove built-in templates that are not in use
• Implement strong access controls on certificate template permissions
• Use security groups to manage enrollment permissions
• Avoid enabling the 'ENROLLEE_SUPPLIES_SUBJECT' flag unless absolutely necessary
• Regularly review and update certificate template settings

Implement comprehensive auditing and monitoring for AD CS activities, including certificate requests, issuance, and template modifications.

• Enable and configure certificate request logging
• Implement a Security Information and Event Management (SIEM) system
• Set up alerts for suspicious activities, such as high-volume certificate requests or changes to CA configurations
• Regularly review and analyze AD CS-related logs
• Implement automated tools for continuous monitoring of AD CS components

Apply security best practices to CA servers, including regular patching, secure configurations, and network isolation.

• Keep CA servers up-to-date with the latest security patches
• Implement strong authentication mechanisms, including multi-factor authentication for CA administrators
• Use dedicated, hardened servers for CA roles
• Implement physical security measures for CA servers
• Regularly perform vulnerability assessments and penetration testing on CA infrastructure

Use network segmentation to limit access to AD CS servers and protect them from potential lateral movement attacks.

• Place CA servers in a separate, restricted network segment
• Implement firewalls and access control lists (ACLs) to restrict traffic to and from CA servers
• Use VLANs or network microsegmentation to isolate CA infrastructure
• Implement secure protocols (e.g., HTTPS) for all AD CS web enrollment endpoints
• Consider implementing a bastion host for administrative access to CA servers

Conduct regular security assessments of your AD CS infrastructure to identify and address potential vulnerabilities.

• Perform periodic internal security audits of AD CS components
• Engage third-party security firms for independent assessments
• Conduct regular penetration testing focused on AD CS infrastructure
• Use automated tools to scan for misconfigurations and vulnerabilities
• Implement a continuous improvement process based on assessment findings

Enforce strong authentication mechanisms for all AD CS-related operations and administrative access.

• Implement multi-factor authentication (MFA) for CA administrators
• Use smart cards or virtual smart cards for administrative access
• Enforce strong password policies for all AD CS-related accounts
• Implement Privileged Access Workstations (PAWs) for administrative tasks
• Consider using Windows Hello for Business for certificate-based authentication

Implement robust processes for managing the entire lifecycle of certificates, from issuance to revocation.

• Develop and enforce policies for certificate issuance, renewal, and revocation
• Implement automated certificate lifecycle management tools
• Regularly audit and clean up expired or unused certificates
• Ensure timely revocation of compromised or no longer needed certificates
• Implement short certificate lifetimes to limit the impact of potential compromises

Develop and maintain an incident response plan specifically for AD CS-related security incidents.

• Create detailed playbooks for various AD CS attack scenarios
• Conduct regular tabletop exercises to test the incident response plan
• Establish clear roles and responsibilities for incident response team members
• Implement procedures for rapid revocation of compromised certificates
• Develop a communication plan for stakeholders in case of a security incident