IEC 62443: A Standards-Based Approach to OT Cybersecurity

Why OT needs its own security standard

IT security is built around confidentiality first. In operational technology (OT) the priorities are reversed: availability and safety come before everything, because a stopped or misbehaving process can hurt people and production. IEC 62443 (also published as ISA/IEC 62443) was written specifically for industrial automation and control systems, which is why it has become the reference standard for OT security worldwide. If you are new to the topic, start with OT cybersecurity basics.

How the series is organised

IEC 62443 is a family of documents grouped by audience:

• General — concepts, terminology and models.
• Policies & procedures — for the asset owner running the security programme.
• System — requirements for integrators designing a secure solution.
• Component — requirements for the product suppliers who build the devices.

The point is that security is a shared responsibility across owner, integrator and vendor — not a single product you buy.

Zones, conduits and security levels

Two ideas do most of the practical work:

• Zones and conduits — you group assets with similar security needs into zones, and control every communication path between them through defined conduits. This is network segmentation with a rulebook.
• Security Levels (SL 1–4) — each zone is assigned a target level based on the threat it faces, from casual/accidental (SL1) up to a sophisticated, well-resourced attacker (SL4).

The seven foundational requirements

Every requirement in the standard maps back to seven foundations: identification and authentication control, use control, system integrity, data confidentiality, restricted data flow, timely response to events, and resource availability. They are a useful checklist even before formal certification.

How to apply it in practice

1. Inventory your OT assets and map how they communicate.
2. Run a risk assessment and define zones and conduits.
3. Set a target security level for each zone.
4. Close the gaps — segmentation, access control, monitoring — and keep reviewing.

How iSquare helps

iSquare Resources helps industrial operators assess, segment and harden their control networks in line with IEC 62443 — see our OT cybersecurity services. To review your plant’s exposure, get in touch.