// CATEGORY · HANS STUDY POSTS
OT and ICS
5 posts filed under OT and ICS. Practitioner technical writing by Hans Study, ordered most recent first.
IEC 62443 Zones and Conduits for a Small Plant, Worked Through
A worked IEC 62443 zones and conduits example for one small site with 3 PLCs, an HMI, a historian, an engineering workstation, and a vendor remote link, with th...
Building an OT Asset Inventory Without Active Scanning
How to build an inventory of PLCs, HMIs, drives, and switches on a control network without scanning it, using passive monitoring, switch tables, project files, ...
The Purdue Model in Practice Versus on Paper
Where real plants blur the Purdue levels, what the Level 3.5 industrial DMZ is for, and which gaps to fix first on a small or mid-size control network....
Vendor Remote Access to OT Without the Forgotten VPN
How to give an integrator or equipment vendor remote access to a control network safely, using a jump host, time-bound access, session recording, and MFA, plus ...
Security Controls for OT Networks That Hold Up in Production
The security controls an operational technology network actually needs, applied in a way that respects how plant systems run. Zones and conduits, the iDMZ, prot...