What Is OT Security? Protecting Industrial Control Systems
What is OT Security? OT Security is the protection of Operational Technology, i.e., the hardware and software that controls physical processes in production, energy and infrastructure. This includes industrial control systems, SCADA environments and programmable logic controllers. OT Security follows different priorities than classical IT security, because here the availability of the plant comes above all else.
Key Takeaways
- What it protects: The systems that control machines, plants and physical processes, from the production line to the substation.
- The difference: In OT, availability takes precedence over confidentiality. A patch that takes a plant offline can be more costly than the risk it mitigates.
- The challenge: Twenty-year or longer lifecycles, legacy protocols without authentication and increasing networking with IT.
Why OT Works Differently From IT
In classic IT security, the typical sequence is confidentiality, integrity, availability. In OT, the order is reversed. Availability comes first, because a stalled production line or a failed transformer station immediately has physical and economic consequences. Security in the sense of safety, meaning protection of people and the environment, adds an additional dimension.
The timeline also differs. While IT systems are often replaced within a few years, plants run for twenty years or more. Many classic controllers use protocols such as Modbus or Profinet that were originally developed without authentication. Newer profiles and gateway security measures can mitigate risk, but in existing installations, securing the environment often falls to network design. Updating requires scheduled maintenance windows rather than ad‑hoc deployments.
Production systems often remain in operation for this long, far beyond the lifecycle of classic IT systems
Source: BSI
Where Risks Arise
For a long time, OT networks were physically isolated from the outside world. This separation is loosening because remote maintenance, data analytics, and connections to corporate systems offer benefits. With networking, the attack surface expands. A compromised IT network can thus become an entry point into production.
Adding to the complexity, many facilities lack built‑in security features and cannot be easily retrofitted. Classic IT tools such as aggressive vulnerability scans can even disrupt sensitive controls. OT security therefore requires tailored approaches rather than simply transplanting IT practices.
First Steps in OT Security
- ✓Create a complete inventory of all OT assets and protocols
- ✓Segment OT networks from IT and control the interfaces
- ✓Secure and log remote maintenance access
- ✓Adapt response plans to OT-specific factors such as maintenance windows
The Framework for OT Security
As the central standard, the IEC 62443 series of standards has become established. It addresses operators, integrators and manufacturers and describes security requirements throughout the lifecycle of a plant, including risk assessment with zones and conduits (Part 62443-3-2) as well as system requirements and security levels (Part 62443-3-3). In Germany, the BSI (Federal Office for Information Security) classifies OT, among other things, within the IND modules of the IT-Grundschutz Compendium, such as IND.1 Process control and automation technology. As a US reference, NIST SP 800-82 complements the protection of industrial control systems. The Purdue model is often used as a structural model, separating levels from field control up to corporate IT.
Regulatorily, OT is gaining increased attention. NIS2 (Network and Information Security Directive 2) and the KRITIS framework (Critical Infrastructure) cover many operators of industrial plants. For the DACH industry, with its strong manufacturing base, OT security has become a central element of the duty to achieve cyber resilience.
How IT and Operational Technology (OT) Come Together
For a long time, IT and Operational Technology (OT) teams worked separately, with their own goals and languages. IT thought in patch cycles and confidentiality, while Operational Technology (OT) focused on availability and plant safety. With increasing networking, this separation can no longer be maintained. An attack that starts in the office network can otherwise end up in production.
The path forward lies in shared governance rather than one side taking over the other. It makes sense to have cross‑cutting responsibility, often at the CISO level, that oversees both IT and Operational Technology (OT) security under one roof, without ignoring the specifics of Operational Technology (OT). Joint risk assessments, coordinated response plans, and a shared situational picture gradually bring the two worlds together.
Supply Chain Perspective
An often underestimated risk in OT is external access. Plants are frequently maintained remotely by manufacturers or integrators, with extensive rights and their own access points. Each of these access points is a potential entry point that must be treated with the same care as internal accounts.
Smart approaches involve controlled, audited remote maintenance accesses instead of permanently open connections. Access is only granted when needed, tied to a specific person, and recorded. Additionally, security requirements should be incorporated into supplier contracts to ensure the chain from manufacturer to plant is traceable and secured.
Frequently Asked Questions
Every question is locked. A tap unlocks the answer.
What is the difference between IT and OT?
IT processes information, while OT controls physical processes. In IT, confidentiality is usually paramount, whereas in OT, availability and the safety of people and systems are prioritized.
What do ICS, SCADA and SPS mean?
ICS is the umbrella term for industrial control systems. SCADA refers to systems for monitoring and controlling distributed processes. SPS stands for programmable logic controllers, which regulate individual machines.
Why can’t you just patch OT?
Plants often run around the clock. An update can disrupt operations or jeopardize certification. Patches require scheduled maintenance windows and thorough testing, rather than being applied spontaneously.
Which standard applies to OT-Security?
As the central reference, the IEC 62443 standards series serves. It defines requirements for operators, integrators, and manufacturers throughout the entire lifecycle.
Is OT-Security covered by NIS2?
Often the answer is yes: NIS2 and the KRITIS framework bring many operators of industrial and infrastructure facilities under security obligations for their OT.
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