The bridge
If you've done this in safety practice…
…then you've already covered most of IEC 62443. The concepts are parallel — different names, same logic.
IEC 62443
The standard — plain English
IEC 62443 is the cybersecurity equivalent of IEC 61511. Here's what you need to know about it.
What is it?
IEC 62443 is the international standard for cybersecurity in Industrial Automation and Control Systems (IACS). It covers everything from security management (Part 2) to system requirements (Part 3) to component requirements (Part 4).
Who does it apply to?
Any organisation operating or supplying industrial control systems — oil & gas, water, power, manufacturing, chemicals. If you work with PLCs, DCS, SCADA, or SIS, IEC 62443 applies to your environment.
How does it relate to IEC 61511?
They're complementary. IEC 61511 addresses safety integrity — can your SIS detect and respond to a process hazard? IEC 62443 addresses security integrity — can your systems resist deliberate attack? A cyber attack on your SIS could undermine your SIL.
Where do I start?
Start with IEC 62443-2-1: it describes the security management system requirements — policies, risk assessment, and the security lifecycle. If you already have a functional safety management system, most of the structure is already familiar.
Getting started
5 practical first steps
No jargon. No “install a firewall.” These are actions any controls engineer can take, using existing skills and tools.
01
Draw your network boundary
Identify where your OT network ends and the IT or internet-facing network begins. This is your "zone boundary" in IEC 62443 terms — equivalent to drawing your SIS boundary in a HAZOP. If you can't draw it, you can't protect it.
02
Know what's on your OT network
List every PLC, HMI, SCADA server, historian, and engineering workstation. Focus on what's safety-related first. An asset you don't know about is a vulnerability you can't manage — the same principle applies in your SIS layer.
03
Check what can talk to what
Review your managed switch configs and firewall rules. Can your HMI reach the internet? Can IT systems initiate connections to your DCS? Each unexpected path is a conduit that may not be in your threat model.
04
Sign up for vendor advisories
Every major OT vendor (Siemens, Rockwell, ABB, Honeywell, Schneider) publishes security advisories. Subscribe to your vendors' advisory RSS feeds or mailing lists — knowing about a vulnerability is the first step to addressing it.
05
Establish a patch review process
You already have a Management of Change process for safety systems. Apply the same discipline to firmware and software updates: test in a staging environment, document changes, schedule a maintenance window, and verify functionality after patching.
Terminology
Terms you'll encounter — translated
CVE
A numbered ID for a known vulnerability in a specific product. Think of it as a defect report number — CVE-2024-1234.
CVSS score
A 0–10 severity score. 9.0+ is Critical — treat like a SIL 3/4 demand rate. Action required.
IACS
Industrial Automation and Control System — the IEC 62443 umbrella term for everything you operate: PLCs, DCS, SCADA, HMIs.
Security Level (SL)
IEC 62443's SIL equivalent for cyber. SL 1–4. SL 2 is the most common target for process industry systems.
Zone / conduit
A logical grouping of assets (zone) and the controlled communication path between groups (conduit). Like physical segregation, but for networks.
Lateral movement
An attacker moving from one compromised device to another — like a process fault propagating because there are no isolation valves.
Firmware
The embedded software inside your PLC, RTU, or HMI. Equivalent to the safety logic in your SIS — changes need MoC.
Patch
A vendor-released software fix for a vulnerability. Equivalent to corrective maintenance — needs testing and a change window.
Know what applies to you
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