Guides
OT segmentation guides
Plain guides to the models and standards behind an OT firewall review, and what each one asks of the rules between zones.
- The Purdue model for OT firewall reviews
- What the Purdue model levels mean, why firewall rules between adjacent levels matter, and which paths an OT firewall review should question.
- IEC 62443 zones and conduits for firewall rules
- How ISA/IEC 62443 zones, conduits and target security levels translate into firewall rules, and which IEC 62443-3-3 requirements a firewall review can speak to.
- NIST SP 800-82r3 segmentation guidance for OT
- What NIST SP 800-82 Rev. 3 says about OT network segmentation, firewall rules, DMZs and remote access, and the SP 800-53 controls in its OT overlay.
- What belongs in an industrial DMZ (IDMZ)
- What an IDMZ is for, what usually sits in it, how OT remote access should pass through it, and the firewall paths that show it is being bypassed.
- Any-any firewall rules in OT
- Why an any-any allow fails an OT firewall rule audit, how to tell whether it carries traffic, and how to replace it without breaking production.