AD Hardening: securing Active Directory

AD Hardening refers to the process of securing Active Directory infrastructure by systematically reducing its attack surface. Active Directory remains a primary target in enterprise intrusions because it centralizes authentication, authorization, and group policy enforcement across Windows environments. Attackers who compromise AD gain persistent, domain-wide control. Effective AD Hardening requires implementing a tiered administrative model that isolates Tier 0 assets (domain controllers, PKI, ADFS) from Tier 1 servers and Tier 2 workstations. This prevents credential theft from spreading laterally across privilege levels. Core hardening actions include disabling legacy protocols such as NTLMv1 and LDAP unsigned bindings, enforcing Kerberos AES encryption, removing unnecessary privileged group memberships, and applying the principle of least privilege to all service accounts. Protected Users security group membership should be enforced for all privileged identities. AdminSDHolder misconfigurations must be audited regularly. AD Hardening is not a one-time task but a continuous operational discipline that directly counters techniques mapped to MITRE ATT&CK TA0004 (Privilege Escalation) and TA0008 (Lateral Movement).

Detecting Active Directory misconfigurations and attacks requires precise log collection from domain controllers. Windows Event ID 4768 and 4769 track Kerberos ticket requests and expose Kerberoasting attempts when RC4 encryption (etype 0x17) is requested for service accounts. Event ID 4625 and 4776 capture NTLM authentication failures and pass-the-hash indicators. Event ID 4728, 4732, and 4756 record additions to sensitive security groups such as Domain Admins or Enterprise Admins. DCSync attacks, used to dump password hashes remotely, generate Event ID 4662 with replication object access rights (DS-Replication-Get-Changes-All). These events must be forwarded to a SIEM such as Microsoft Sentinel, Splunk, or Elastic SIEM with dedicated detection rules. BloodHound Enterprise or PingCastle can continuously assess AD attack paths and misconfiguration drift. LDAP query logging (Event ID 1644 on domain controllers) exposes reconnaissance activity from tools like SharpHound or ldapdomaindump. Purple Team exercises using atomic tests from the Atomic Red Team framework help validate detection coverage across these specific event categories before real adversaries exploit blind spots.

Red Team operators target Active Directory misconfigurations using a well-documented attack chain. Kerberoasting extracts service account hashes via TGS requests and cracks them offline using Hashcat. AS-REP Roasting targets accounts with Kerberos pre-authentication disabled. BloodHound maps privilege escalation paths by identifying ACL abuses, such as WriteDACL or GenericAll permissions on high-value objects. Pass-the-Hash and Pass-the-Ticket attacks reuse harvested credentials without knowing the cleartext password. To harden against these techniques, organizations must deploy LAPS (Local Administrator Password Solution) to randomize local admin passwords on all workstations, preventing lateral movement via shared credentials. Privileged Access Workstations (PAW) must be enforced for all Tier 0 and Tier 1 administration. Fine-Grained Password Policies should set minimum 25-character passphrases for service accounts to resist offline cracking. Managed Service Accounts (gMSA) eliminate static passwords entirely for service identities. ACL auditing tools such as ADACLScanner or BloodHound's built-in analysis detect dangerous delegation rights before attackers exploit them. Disabling the print spooler service on domain controllers removes PrintNightmare and SpoolFool attack vectors that enable SYSTEM-level privilege escalation on critical infrastructure.