Topic starter
11/07/2026 8:23 pm
TL;DR: CISA’s 2025 guidance frames OT asset inventory as a prerequisite for modern defensible architecture, arguing that organisations cannot protect what they cannot see and must pair discovery with taxonomy, lifecycle management, and segmentation. Elisity’s analysis shows the governance gap is now operational, not theoretical.
Editorial analysis by NHI Mgmt Group, based on content published by Elisity: “OT Asset Inventory: CISA's 2025 Guide to Modern Defensible Architecture”.
Key questions
Q: What breaks when OT asset inventory is incomplete?
A: Incomplete OT asset inventory breaks segmentation, vulnerability prioritisation, and incident response because security teams cannot reliably tell which devices exist, where they are, or what they connect to.
Q: Why does OT inventory change the risk model for microsegmentation?
A: OT inventory changes the risk model because microsegmentation only works when policies are tied to accurate asset identity and communication context.
Q: How should security teams classify OT assets for governance?
A: Security teams should classify OT assets by criticality, function, and dependency rather than by simple device counts.
Practitioner guidance
- Map every OT asset to a living inventory record Capture device type, communication path, criticality, physical location, and ownership in one governed system, then reconcile it continuously against network observations and maintenance data.
- Build taxonomy before segmentation rules Classify assets by function and criticality so that zones, conduits, and allowlists reflect operational importance instead of raw network topology.
- Prioritise unmanaged and legacy devices first Focus discovery and containment on devices that cannot host agents, use proprietary protocols, or rely on outdated firmware, because these are the hardest to defend once missed.
Bottom line: OT asset inventory is no longer a reporting exercise in industrial environments; it is the prerequisite data layer for segmentation, lifecycle governance, and incident response.
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11/07/2026 8:53 pm
OT asset inventory is now a governance primitive, not an admin task. CISA's framing moves inventory out of documentation and into architecture, because control boundaries depend on knowing what is present, what it does, and what it can reach. In OT, that makes discovery a prerequisite for defensible segmentation and incident containment. Practitioners should treat inventory quality as a board-relevant control outcome.
A few things that frame the scale:
- Only 5.7% of organisations have full visibility into their service accounts, according to the Ultimate Guide to NHIs.
A question worth separating out:
Q: When should organisations treat OT asset inventory as a control requirement?
A: Organisations should treat OT asset inventory as a control requirement whenever they need to enforce segmentation, support incident response, or manage legacy devices that cannot run agents. At that point, inventory is not supporting the control, it is enabling it. Without it, policy cannot be consistently applied or defended.
👉 Read our full editorial: OT asset inventory is becoming the basis for defensible architecture