OT (Operational Technology) refers to systems that control physical processes on a factory floor — PLC controllers, SCADA systems, industrial robots — as opposed to IT, which manages data and information. OT cybersecurity needs a different approach than IT, because priorities are reversed: IT puts confidentiality first, while OT puts continuity and the process’s physical safety first.
Quick Overview
What you’ll learn:
- How OT differs from IT in security priorities
- The Purdue model as a starting point for OT network segmentation
- A first-steps plan for rolling out OT security in a manufacturing plant
- The most common mistakes when applying IT practices to an OT environment
Who this article is for:
- IT and OT managers at manufacturing plants planning a first security rollout
- Security specialists moving from classic IT into an industrial environment
- Managers responsible for NIS2 compliance in the manufacturing sector
Reading time: 6 minutes
How OT Differs From IT in Security Priorities
Classic IT security ranks priorities using the CIA triad: confidentiality, integrity, availability — in that order. In an OT environment, that order is reversed: availability (keeping a production line running) and physical safety come first, because an outage in a control system can mean stopped production or, in the worst case, a risk to people.
That difference has practical consequences: a standard security patch that IT installs automatically overnight may, in OT, require a scheduled maintenance window, because restarting a PLC controller stops the production line. IEC’s 62443 standard, devoted to industrial network security, notes that mechanically transplanting IT practices into OT without accounting for this shift in priorities is one of the more common sources of trouble in rollouts.
The Purdue Model as a Starting Point for OT Network Segmentation
The Purdue model divides a manufacturing plant’s architecture into levels — from level 0 (physical sensors and actuators) through level 1 (PLC controllers), level 2 (SCADA/HMI supervisory systems), level 3 (production operations management), up to level 4-5 (the corporate IT network). The key security principle that follows from this model is segmentation: network traffic between levels should pass through controlled, monitored points of contact, rather than flow freely between the corporate network and the process-control layer.
A demilitarised zone (DMZ) between level 3 and level 4 is the most commonly recommended architectural element — it lets operational data (production reporting, say) be exchanged with IT systems without directly connecting the corporate network to the layer that controls the physical process.
A First-Steps Plan for Rolling Out OT Security
- Inventory every OT device on the network — surprisingly often, plants don’t have a complete, up-to-date list of controllers and systems connected to the network, which blocks any further action.
- Map the current network architecture against the Purdue model — identify where IT and OT networks touch without a controlled crossing point.
- Introduce segmentation between levels, starting at the IT/OT boundary — even basic segmentation limits the blast radius of a potential incident.
- Plan a patch-management process that accounts for maintenance windows — patching in OT needs coordination with the production schedule, and can’t be automatic the way it is in IT.
- Introduce network traffic monitoring at the OT layer — detecting anomalies in an industrial network that historically was rarely monitored for security.
In its materials on ICS/SCADA systems, ENISA notes that many incidents in industrial environments stem not from advanced attacks, but from a lack of basic network segmentation and outdated systems that were never designed to be connected to a corporate network.
The Most Common Mistakes When Applying IT Practices to an OT Environment
Common mistakes include: installing security patches without accounting for production maintenance windows, treating network segmentation as an optional improvement rather than a security foundation, and assuming vulnerability-scanning tools designed for IT are safe to run against an OT network — aggressive scanning can destabilise load-sensitive industrial controllers.
Read Also
- IT/OT/ICS Cybersecurity — Comprehensive Guide for Industry and Critical Infrastructure (2026) — a deeper guide covering NIS2, compliance and a competency map by role
- Cybersecurity Challenges in Industry 4.0 — a wider context on security challenges in manufacturing’s digital transformation
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This topic connects to the 5G and IoT: The Synergy of Future Technologies and Amazon Web Services (AWS) IoT Greengrass — Edge Computing courses. Check the program and sign up to build your skills with EITT’s experts.
Frequently Asked Questions (FAQ)
How does OT differ from IT in security priorities?
IT prioritises data confidentiality. OT prioritises availability — keeping a production line running — and physical safety, because an outage in a control system can stop production or endanger people.
What is the Purdue model and what is it used for?
It’s a model that divides a manufacturing plant’s architecture into levels, from physical sensors up to the corporate IT network. It’s used for network segmentation — traffic between levels should pass through controlled points of contact, not flow freely.
Why can’t OT systems be patched the same way IT systems are?
Because restarting or updating a PLC controller can stop a production line — patching in OT needs a scheduled maintenance window coordinated with the production schedule, unlike the automatic updates typical of IT.
Are standard IT vulnerability-scanning tools safe on an OT network?
Not always — aggressive scanning designed for IT systems can destabilise load-sensitive industrial controllers, so scanning an OT environment requires tools and methods adapted to how those systems behave.