Active Directory (AD) is a critical component for managing Windows-based systems in both IT and Operational Technology (OT)/Industrial Control Systems (ICS) environments. However, integrating IT AD with OT AD can introduce significant security risks.
Key Reasons to Keep IT and OT AD Separate
1. Preventing Lateral Movement – If attackers compromise IT AD, they can pivot into OT networks if trusts exist.
2. Different Security Policies – OT systems often require stricter controls, and mixing policies can weaken security.
3. Reducing Attack Surface – Separate forests eliminate pathways for attackers to move from IT to critical OT infrastructure.
Best Practices for Securing OT Active Directory
- Deploy a Separate AD Forest for OT – Isolate OT systems from IT AD entirely.
- Disable Trust Relationships – Ensure no trusts exist between IT and OT domains.
- Implement Strong Password Policies – Enforce longer, complex passwords for OT admin accounts.
- Use Dedicated Group Policy Objects (GPOs) – Customize GPOs for OT systems to enforce security baselines.
You Should Know: Key Commands and Steps for Secure AD Management
1. Creating a Separate AD Forest for OT
Install AD Domain Services Install-WindowsFeature -Name AD-Domain-Services -IncludeManagementTools Promote a new forest for OT Install-ADDSForest -DomainName "ot.local" -DomainMode "WinThreshold" -ForestMode "WinThreshold" -InstallDNS
- Disabling Trusts Between IT and OT AD
Check existing trusts Get-ADTrust -Filter Remove a trust (if mistakenly created) Remove-ADTrust -Identity "it.local" -Confirm:$false
3. Hardening OT AD Security
Enforce strong password policies Set-ADDefaultDomainPasswordPolicy -Identity "ot.local" -MinPasswordLength 14 -ComplexityEnabled $true Disable unnecessary services (e.g., SMBv1) Disable-WindowsOptionalFeature -Online -FeatureName "SMB1Protocol" -NoRestart
4. Monitoring for Suspicious AD Activity
Enable detailed AD audit logging Auditpol /set /subcategory:"Directory Service Access" /success:enable /failure:enable Check for unusual login attempts (Security Event Log) Get-WinEvent -LogName "Security" -FilterXPath "[System[EventID=4625]]"
5. Isolating OT Systems with Firewall Rules
Block IT-to-OT AD traffic New-NetFirewallRule -DisplayName "Block IT-OT AD Traffic" -Direction Inbound -RemoteAddress "192.168.1.0/24" -Protocol TCP -LocalPort 389,636 -Action Block
What Undercode Say
Keeping IT and OT Active Directory separate is not just a recommendation—it’s a necessity. Attackers constantly look for ways to move from less-secure IT networks into critical OT environments. By implementing strict isolation, enforcing strong authentication, and continuously monitoring AD activity, organizations can significantly reduce the risk of a catastrophic breach.
Additional Security Measures
- Regularly Patch OT Systems – Use WSUS offline updates if OT systems are air-gapped.
- Implement Network Segmentation – VLANs and firewalls should restrict unnecessary communication.
- Monitor for Anomalies – Deploy SIEM solutions to detect unusual AD access patterns.
Expected Output:
A hardened, isolated OT AD environment with no trust relationships to IT AD, strong password policies, and continuous monitoring for unauthorized access attempts.
Would you like further details on securing specific OT systems like historians or engineering workstations? Let us know in the comments!
References:
Reported By: Mikeholcomb Connecting – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
