security level

A security level is a defined degree of protection against intentional or accidental threats to systems, data, or physical assets. In industrial and regulated environments, it commonly refers to a graded set of cybersecurity or physical security requirements that must be met for a system, zone, or asset.

In industrial and OT cybersecurity

In operational technology (OT) and industrial control system (ICS) contexts, a security level often refers to a formal, discrete rating that describes how resistant a system is to cyber attacks from defined types of adversaries. Frameworks such as IEC 62443 use numbered security levels to specify progressively stronger requirements for:

• Access control and authentication
• System integrity and hardening
• Network segmentation and communication security
• Monitoring, detection, and incident response
• Maintenance and change management practices

In this usage, the security level applies to defined scopes such as devices, systems, zones, or conduits. It is set based on a risk assessment, threat model, and impact analysis, then implemented through technical and procedural controls. The level itself does not guarantee security; it reflects the intended rigor of applied controls.

Operational meaning in manufacturing

Within manufacturing operations, security levels may be used to:

• Classify production networks or cells (for example, segregated OT zones) according to required protection
• Set minimum security expectations for equipment suppliers and system integrators
• Drive requirements for user roles in MES, historians, or SCADA systems
• Guide patching, remote access, and backup procedures based on the criticality of assets

Security levels are typically documented in security policies, system specifications, or zone & conduit models and are used as a reference during design, implementation, and assessment activities.

Common confusion

• Security level vs. safety integrity level: A security level addresses protection against malicious or unauthorized actions. A safety integrity level (SIL) in functional safety addresses the reliability of safety functions against hazards, not cybersecurity.
• Security level vs. security control: A security level is an overall target or rating. Security controls are individual technical or procedural measures used to achieve that level.
• Security level vs. compliance status: A security level does not in itself confirm regulatory or standard compliance. It is a design and management construct that may be aligned with standards and then verified through separate assessments.

Relation to IEC 62443 context

In the context of IEC 62443, security levels are central to specifying cybersecurity requirements for industrial automation and control systems. The standard defines how asset owners, system integrators, and product suppliers can use graded security levels to scope, design, and assess controls over the full lifecycle. The chosen level is based on risk and threat assumptions and must be supported by appropriate technical and organizational measures.