Topic starter
10/07/2026 9:12 pm
TL;DR: CISA’s OT Zero Trust guidance argues that air gaps are no longer a reliable security assumption because remote access, cloud-connected interfaces and IT/OT integration create unavoidable paths into critical systems, according to Appgate’s analysis of the guide. Logical segmentation, identity-centric access and continuous validation now define practical OT defence, not perimeter myths.
Editorial analysis by NHI Mgmt Group, based on content published by Appgate: “CISA's New Zero Trust Guidance for OT: Modernizing the 'Air Gap' and Designing for DDIL with AppGate ZTNA”.
Key questions
Q: What fails when organisations treat OT as air-gapped in practice?
A: The failure mode is assuming that physical or logical separation still exists after remote support, cloud integration and vendor connectivity are added.
Q: Why do shared IT and OT access paths increase operational risk?
A: Shared access paths increase risk because they connect business systems to process and safety environments through the same trust relationship.
Q: How can security teams tell whether Zero Trust is applied consistently?
A: A consistent Zero Trust programme applies the same verification, least-privilege, and review logic to employees, contractors, and vendors.
Practitioner guidance
- Map every OT access path to an explicit owner Inventory remote vendor links, cloud-connected interfaces and IT-to-OT integrations, then assign a business owner and technical approver to each route.
- Enforce segmentation as a live policy Treat segmentation rules as enforceable controls that can be validated and updated, rather than as a one-time network design choice.
- Gate OT connectivity on identity and device context Require strong authentication and device posture checks before any remote or third-party session can reach OT assets.
Bottom line: OT security breaks when organisations rely on a symbolic air gap instead of enforced segmentation, identity checks and continuous monitoring.
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10/07/2026 9:35 pm
The air gap is now a governance fiction, not a security control. Once remote support, cloud interfaces and IT/OT integration exist, the question shifts from preserving perfect isolation to enforcing explicit, monitored trust boundaries. That makes identity, segmentation and monitoring the operating model for OT defence, not optional enhancements. Practitioners should govern OT access as a continuous control problem, not a perimeter design problem.
A few things that frame the scale:
- 90% of IT leaders say properly managing NHIs is essential for a successful zero-trust implementation, according to the Ultimate Guide to NHIs.
A question worth separating out:
Q: What should critical infrastructure teams do when they must preserve both access and isolation?
A: They should use governed, identity-based access that is tightly scoped to the required OT asset and supported by segmentation that can survive degraded connectivity. The operational goal is not to pretend no route exists, but to make any route deliberate, observable and reversible. That approach supports both continuity and containment.
👉 Read our full editorial: Zero Trust for OT is replacing the air gap assumption