Designed a multi-forest Active Directory architecture for operational technology environments, establishing secure identity management across OT DMZ, SCADA, and energy management system (EMS) domains.
The Challenge
A major utility provider was upgrading their platforms and needed to establish secure identity and access management for their operational technology environment. The project required separating OT systems from corporate IT while maintaining necessary integration points for operations staff. The environment included SCADA systems, energy management systems controlling generation and distribution, and partner connectivity zones. The architecture needed to address specific governance requirements of the Australian Energy Sector Cyber Security Framework (AESCSF) while enabling both ICT operations teams and OT system administrators to manage their respective domains effectively.
Our Approach
We designed a multi-forest, multi-domain Active Directory architecture with clear security boundaries between IT and OT environments. The solution established a root domain topology incorporating an OT DMZ layer that acts as an aggregation point between corporate IT and operational technology systems. A separate forest for the OT DMZ environment was established with dedicated domain controllers, integrating the OT Administrator (OTA) role to support EMS operations through a defined one-way trust relationship. The EMS environment itself comprises a single-forest, two-domain architecture with distinct DMZ and Control domains, segmented using Organisation Units across Production, Development, Staging, QAS, Training, and Partner zones. One-way and selective trusts between forests and domain controllers enable appropriate segmentation while allowing operational teams to manage multiple environments using single sign-on.
Results
Multi-forest architecture with dedicated OT DMZ as secure aggregation layer
Root domain topology supporting EMS, SCADA, and partner SCADA connectivity
OTA role design and integration enabling OT administrators to support EMS operations
Single-forest two-domain model separating DMZ and Control environments
Organisation Unit structure for granular access control across environments
Trust relationship design meeting AESCSF governance requirements
Detailed technical design enabling implementation by internal teams
Further Reading
The Purdue Enterprise Reference Architecture remains foundational for OT security, but modern requirements demand adaptation. Explore how to extend the model for cloud connectivity, remote access, and micro-segmentation.
Navigate the Australian Energy Sector Cyber Security Framework with actionable guidance on C2M2-based domains, maturity levels, and building a sustainable compliance program aligned with the SOCI Act.
Successful IT/OT convergence requires more than technology integration. Learn how to navigate cultural divides, establish governance frameworks, and implement security that respects operational constraints.
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