Topic starter
25/10/2026 11:08 am
TL;DR: Firewall-led segmentation in OT becomes brittle as environments change, because static IP and port rules struggle to enforce least privilege, vendor access, and east-west control across zones and conduits, according to Xage Security. The governance gap is not perimeter defence but identity-aware enforcement that can adapt without constant rule churn.
Editorial analysis by NHI Mgmt Group, based on content published by Xage Security: “OT Segmentation vs Firewalls: Why Zero Trust Is More Effective”.
Key questions
Q: What breaks when OT segmentation depends on static network rules?
A: Static OT segmentation breaks when network location is no longer a reliable proxy for trust.
Q: Why does identity matter in OT segmentation decisions?
A: Identity matters because OT access is increasingly about who or what is connecting, not just which network segment they are on.
Q: How do organisations prevent vendor access from becoming permanent?
A: They scope vendor connectivity to named assets, require approved time windows, and revoke access automatically when the maintenance task ends.
Practitioner guidance
- Redesign segmentation around identity-aware policy Use roles, device identity, and time-bound access to define who can reach each OT zone instead of relying on static IP and port rules.
- Inventory and retire permanent firewall exceptions Review legacy rules that were created for temporary maintenance or vendor access and remove any pathway that no longer has an active business need.
- Bind third-party access to explicit expiry Require vendor sessions to be scoped to named assets and time windows so maintenance access does not become standing access.
Bottom line: Firewall-centric segmentation can preserve boundaries, but it does not scale well when OT environments change frequently and need identity-aware access decisions.
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