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Securing Domain Controllers

Domain Controllers are the crown jewels of your network — every security recommendation in this module converges on one goal: making DCs as hardened, monitored, and isolated as possible.

Domain Controllers are the most critical servers in your network. They hold the NTDS.dit database with every user's password hash, they issue every Kerberos ticket, and they replicate all changes across the domain. If an attacker compromises a DC, game over — they own everything. Securing DCs means: keeping them physically secure (locked server rooms), minimizing what runs on them (no extra software, no browsing, no email), restricting who can access them (only Tier 0 admins from PAWs), keeping them updated (prioritize DC patching), monitoring everything (detailed audit logging forwarded to a SIEM), and isolating them on the network (dedicated VLANs with firewall rules).

In a medieval castle, the keep is the innermost fortification — the last line of defense housing the treasury and the lord. It has the thickest walls, the fewest doors, a dedicated garrison, and constant watchtower surveillance. No peasant or merchant wanders through the keep. Domain Controllers are the keep of your AD castle: they store every credential, authorize every access, and replicate every change. Hardening them means thicker walls (network isolation), fewer doors (minimal services), a dedicated garrison (restricted admin access), and watchtower surveillance (continuous monitoring).

Try It Yourself

Key Takeaways

  1. DCs hold every credential in the domain — compromise one and you own everything.
  2. Disable Print Spooler on DCs to prevent PrinterBug coercion attacks.
  3. Enforce SMB signing and LDAP signing to prevent relay attacks against DCs.
  4. Restrict DC access to Tier 0 admins on PAWs only — deny logon for everyone else.
  5. Prioritize DC patching: critical AD vulnerabilities must be patched within 24-48 hours.
Why Should I Care?

Every AD attack ultimately targets Domain Controllers. Hardening DCs is the single highest-impact defensive investment you can make — it raises the bar for every attack technique from credential theft to domain dominance.

Related Topics

Tiered Administration ModelLAPS & Credential GuardAD Security Event MonitoringNTLM Relay Attacks
Sources
Microsoft Defender for Identity
SourceSudo

Content sourced from Microsoft Documentation, MITRE ATT&CK Framework, NIST SP 800-63/171, adsecurity.org (Sean Metcalf), SpecterOps research, and SANS Reading Room. For educational purposes only.

MITRE ATT&CKADSecurity.org