Identity is now the main security boundary, especially as IT, cloud, and operational technology (OT) networks collide. As organizations modernize and connect their industrial control systems (ICS) with enterprise cloud services, the traditional “trusted internal network” mindset is no longer enough.
A true Zero-Trust Architecture (ZTA) starts with rethinking identity and access across all layers — from Microsoft Entra ID to PLC (a specialized, low-level industrial control devices that do not use modern identity protocols like OAuth or OpenID Connect). Instead, integration is achieved through a secure, intermediary architecture involving gateways and specialized edge software.
1. Why Zero Trust Matters in Hybrid + OT Environments
Hybrid and OT networks are notoriously complex:
- Legacy systems without native identity awareness.
- Air-gapped zones slowly opening to cloud-based analytics.
- Mix of Windows, Linux, and proprietary vendor systems.
- Inconsistent security domains across IT and production.
Attackers take advantage of gaps between IT and OT, using weak credentials and outdated authentication. Zero Trust addresses this by enforcing “never trust, always verify” at every access point.
2. Foundational Principles for Zero-Trust Identity
- Strong Identity Provider (IdP) Integration:
Centralize authentication through a trusted IdP such as Microsoft Entra ID or similar, federated to both cloud and on-prem realms. - Least Privilege Access:
Move away from static roles to Just-In-Time (JIT) and Just-Enough-Access (JEA) using Privileged Access Management (PAM) tools. - Conditional Access & Context Awareness:
Access mechanisms should adjust dynamically, taking into account device integrity, geographic location, time parameters, and user risk indicators.
- Segmentation by Identity Zones:
Instead of having one big, open network where everything can talk to everything, break it into smaller zones based on what they do. For example:
- Enterprise zone for office systems and users
- DMZ (demilitarized zone) for servers that connect to the internet
- Control network for machines and systems running operations or production
Each zone has its own security rules, and access between zones is controlled by identity meaning people and devices must prove who they are and meet certain conditions before they can cross from one zone to another.
In short: don’t treat your network as one big, trusted area create smaller trust zones and make every connection verify who’s asking for access.
3. Extending Zero Trust into OT/ICS
Bringing Zero Trust into OT isn’t about replacing industrial protocols, it’s about overlaying identity-aware gateways and enforcing accountability:
- Introduce Identity Proxies for systems that can’t join a domain (e.g., PLCs, HMIs).
- Use device certificates and mutual TLS to authenticate machine-to-machine connections.
- Deploy jump servers or secure remote access portals that enforce MFA, session recording, and policy-based routing.
- Apply micro-segmentation with tools like Azure Arc or Defender for IoT to separate IT, DMZ, and control layers.
4. Common Design Patterns
- Identity Federation: Connect OT users to corporate identity systems via Entra ID, with conditional access enforcing device compliance.
- PAM Gateways: Provide controlled elevation for engineers needing privileged OT access.
- Digital Twin of Access: Maintain a real-time inventory of who accessed what system, from where, and when a critical audit requirement.
- Hybrid Join Models: Integrate Entra ID cloud workloads with domain-joined OT servers for unified oversight.
5. Governance, Monitoring & Response
Zero Trust isn’t a one-time setup, it’s continuous governance:
- Enable Defender for Identity / Defender for IoT for anomaly detection.
- Align access reviews with NIST 800-207 and ISA/IEC 62443 frameworks.
- Use Microsoft Purview for data classification and Entra ID Access Reviews to regularly prune stale permissions.
- Integrate SIEM/SOAR (e.g., Sentinel, Splunk) to unify logs from IT and OT domains.
6. The End Goal: Unified Trust Fabric
A robust Zero-Trust identity framework integrates IT, cloud, and operational technology into a unified trust architecture. It will ensure that every access request is authenticated, authorized, and subject to ongoing validation. This approach significantly reduces lateral movement, enhances audit capabilities, and supports compliance with standards such as CCCS PBMM, NIST CSF, and NATO AC/35-D/2000.
Final Thoughts
As companies increasingly integrate traditional systems with cloud and operational technology (OT) networks, identity serves as a primary method for managing and securing access. It ensures that only authorized individuals and devices are granted appropriate permissions.
At Al Basit Technology Solutions Ltd., we help organizations build Zero-Trust security designs that are strong enough for defense environments but still practical and easy to use. Our goal is to make sure your systems, whether in the cloud or on the factory floor, stay secure, compliant, and reliable.
