SL-C stands for capability security level in the IEC 62443 family of industrial cybersecurity standards. It describes the security level that an individual component, device, or system is technically capable of supporting when correctly configured and used as intended.
What SL-C represents
SL-C commonly refers to the maximum security capability that can be provided by a product or system with respect to the IEC 62443 foundational requirements (such as identification and authentication control, use control, system integrity, data confidentiality, restricted data flow, timely response to events, and resource availability). It is typically determined by the vendor or by an assessment of the product’s functions and security features.
In operational terms:
- SL-C is a property of a component or system, not of a zone or conduit.
- It describes what that component can support (for example, up to SL 2 or SL 3) if all security features are available and correctly configured.
- It is often used during design, procurement, and engineering to select components that are capable of supporting the target security levels of the intended industrial control system or manufacturing environment.
SL-C does not by itself state that a system is deployed or operated at that security level. It is a measure of capability, not of the actual achieved or maintained security posture in a live plant.
Relationship to other IEC 62443 security levels
IEC 62443 uses several related security level concepts. In this context, SL-C is usually contrasted with:
- SL-T (target security level): the risk-based security level that a zone or conduit in an industrial automation and control system should achieve.
- Achieved/implemented security level: the level actually realized in the field, considering configuration, architecture, procedures, and operational practices.
In many brownfield manufacturing plants, the SL-C of legacy components may be lower than the SL-T defined for modern cybersecurity or regulatory expectations. The difference between SL-C and SL-T then has to be addressed through system architecture, compensating controls, and documented risk management.
Common confusion
- SL-C vs SL-T: SL-C is about what a specific component or system can technically provide. SL-T is about what a zone or conduit should achieve based on risk.
- SL-C vs certification: A stated SL-C does not in itself indicate any official certification or assessment outcome. It is a description of capability, not an audit result.
Use in regulated manufacturing environments
In regulated industrial and manufacturing settings, SL-C is often used as an input to system design, procurement specifications, and cybersecurity risk assessments. For example, engineers may select controllers, HMIs, or data gateways with an SL-C that is compatible with the defined SL-T for a safety-critical process cell, then document any remaining gaps and how they are addressed through policies, network design, or additional controls.