OT zones and conduits: segmentation that follows IEC 62443
How to divide a plant network into zones, control what crosses between them, and why flat OT networks keep making incident reports.
Purdue model
IT/OT layering model underlying segmentation design.
The reference layering enterprise (Level 4–5) through operations (Level 3), supervision (Level 2), control (Level 1), and physical process (Level 0), with a DMZ between IT and OT. A starting sketch for segmentation, per ISA-95 concepts.
See also: ISA-95 · Industrial DMZ · Zones and conduits
Use the concept: Subnet calculator · OT asset inventory template · OT backup & restore test template
In depth
OT backup and restore testing: prove the recovery path
Inventory the files and dependencies needed to recover a control system, set recovery objectives, and test restoration on an isolated target.
OT incident response: a ransomware playbook for plants that can't just stop
Build an OT incident response plan that respects process safety — roles, containment without shutdowns, backups that restore, and tested playbooks.