IEC 62443-Based Zoning Implementation
and Validation Checklist
From Air-Gapped Assumptions to Securely Connected Operations
Industrial environments are no longer isolated. Production networks now exchange data with enterprise IT, remote vendors, analytics platforms, and cloud-connected systems. This convergence has delivered operational efficiency-but it has also erased the natural boundaries that once protected critical infrastructure.
Security today is not about simply deploying firewalls. It is about designing enforceable trust boundaries inside OT environments. That is exactly where structured zoning, aligned with IEC 62443, becomes essential.
This checklist is designed to help asset owners, engineering leaders, and security teams translate standards into implementation-turning theory into defensible architecture that can withstand both cyber threats and operational realities. Developed by OT security practitioners at Shieldworkz, this guide bridges the gap between compliance language and plant-floor execution.
Why this checklist matters now
Many industrial organizations believe they already have “segmentation” because VLANs or legacy Purdue diagrams exist. In practice, those environments often contain:
Flat networks with uncontrolled east-west traffic
Undocumented communication pathways between systems
Shared trust between safety, control, and business assets
Remote access mechanisms that bypass intended controls
Security designs that cannot be validated or audited
When a breach occurs, attackers exploit these invisible connections-not the perimeter. IEC 62443 introduces a powerful concept: zones and conduits defined by risk, consequence, and required security level, not by convenience. But implementing that concept requires structured methodology, engineering alignment, and continuous validation.
What the checklist contains
This is a practical execution guide focused on remediation and program maturity. It is NOT a theoretical standard or a replacement for a full gap assessment. Use it to convert observations into prioritized tasks, assign owners, track SLAs for revalidation and validate mitigation effectiveness against IEC 62443 FRs and Security Level targets.
Asset discovery & inventory - precise steps to enumerate PLCs, HMIs, historians, engineering workstations, safety systems, IIoT endpoints and vendor paths.
Consequence-driven risk assessment - how to use HAZOP/PHA inputs to assign target Security Levels (SL-T) and derive zone logic.
Zone definition rules - unambiguous boundaries, ownership, naming conventions and non-negotiable rules (never mix SLs without compensating controls).
Conduit specification - per-conduit rules: allowed protocols, directionality, authentication and the enforcing control (firewall, data diode, protocol break).
Complementary zoning approaches - Purdue alignment, data-flow clustering, micro-segmentation for high-consequence assets and an overlay zero-trust mindset for mature sites.
Technical implementation - industrial firewall policies, VLAN and DMZ design, data diodes, protocol whitelisting, jump server hardening and SIS segregation guidance.
Documentation requirements - zone & conduit registers, living network diagrams, change controls and exception processes.
Validation & testing - firewall rule audits, passive traffic validation, conduit penetration tests, SIS isolation checks and tabletop exercises.
Ongoing governance - review cadences, MoC integration, continuous monitoring and training to prevent zone erosion.
Key Takeaways From the Checklist
Zoning must be driven by risk and consequence, not convenience
Every zone and conduit must be explicit, owned, and enforceable
Documentation is a security control, not an administrative task
Validation is essential to ensure zones work during real incidents
Governance keeps zoning effective as environments evolve
How Shieldworkz Supports Your Zoning Journey
Implementing IEC 62443 zoning is not just a design exercise-it is an operational transformation. Our approach focuses on ensuring security controls align with how industrial environments actually run. We help organizations:
Translate risk assessments into enforceable zone architectures
Map real-world process flows to secure communication models
Validate segmentation using passive monitoring and scenario testing
Integrate zoning into lifecycle governance and engineering workflows
Prepare environments for audits, modernization, and resilience programs
The goal is not simply compliance-it is building an architecture that continues to function safely under stress, change, and evolving threat conditions.
Ready to get started?
Download the IEC 62443-Based Zoning Implementation & Validation Checklist to convert standards into an executable program. Complete the short form to receive the checklist and a complimentary 15-minute operational review to prioritise your first zoning and validation steps.
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