Active Directory Hardening: Where Should Organizations Start?
Active Directory remains a primary target in enterprise attacks. This article outlines a practical starting point for Active Directory hardening, covering the areas that carry the most risk.
Why Active Directory Hardening Matters
Active Directory (AD) is the identity backbone of most enterprise environments. It controls authentication, authorization, and access to resources across the organization. Because of its central role, Active Directory is a high-value target for attackers. A compromised domain controller or privileged AD account can give an attacker broad access to systems, data, and infrastructure. Despite this, many organizations have AD environments that have grown over years or decades without systematic security review — accumulating legacy configurations, excessive permissions, and outdated settings that increase risk.
Start With a Security Assessment
Before implementing hardening changes, organizations benefit from understanding their current security posture. An Active Directory security assessment identifies the specific risks present in the environment — which privileged accounts exist and whether they are appropriately controlled, what authentication protocols are in use, whether domain controllers are properly secured, how Group Policy is configured, and where excessive delegated permissions exist. This assessment provides a prioritized view of what to address first, rather than applying generic hardening checklists without understanding the specific risk profile of the environment.
Privileged Access and Tier 0 Protections
One of the highest-priority areas in Active Directory hardening is controlling privileged access. This includes reviewing membership in highly privileged groups such as Domain Admins, Enterprise Admins, and Schema Admins — ensuring these groups contain only accounts that genuinely require that level of access. Implementing an administrative tiering model separates Tier 0 assets (domain controllers, AD infrastructure) from lower-tier systems, reducing the risk that a compromised workstation or server account can be used to attack AD directly. Service accounts with excessive permissions, accounts with non-expiring passwords, and accounts that have not been used recently are also common risk areas.
Authentication Hardening
Legacy authentication protocols represent a significant risk in many Active Directory environments. NTLM, while still widely used, is susceptible to relay attacks and credential theft. Where possible, organizations should work toward reducing NTLM usage and enforcing Kerberos. LDAP signing and channel binding should be enabled on domain controllers to prevent LDAP relay attacks. Authentication policies and silos can provide additional controls for Tier 0 accounts. Reviewing and tightening password policies, account lockout settings, and fine-grained password policies is also part of a comprehensive authentication hardening effort.
Group Policy Security Configuration
Group Policy is a powerful mechanism for enforcing security settings across an Active Directory environment, but it can also become a source of risk when GPOs are poorly managed. Overly permissive GPOs, conflicting settings, unlinked GPOs, and GPOs with excessive delegation can undermine security controls or create unpredictable behavior. A Group Policy governance review identifies GPOs that should be cleaned up, settings that should be tightened, and delegation that should be restricted. This is often a significant undertaking in environments where Group Policy has grown organically over many years.
Recovery Readiness
Active Directory hardening should also address recovery readiness. Organizations should have a tested process for restoring Active Directory in the event of a ransomware attack, accidental deletion, or other significant incident. This includes verifying that AD backups exist, are current, and can be successfully restored — and that the recovery process is documented and understood by the team responsible for it. A domain that cannot be recovered is a significant business risk regardless of how well it is hardened.
Reviewing Active Directory security?
IdenForth can help assess your Active Directory environment and identify the highest-priority hardening actions.
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