Glossary · OT cybersecurity
Security level (SL)
Also known as: SL, IEC 62443 security level
German: Security Level (SL)
In IEC 62443, a security level (SL) is a measure from 0 to 4 of the confidence that a zone, conduit or component is free of vulnerabilities and functions as intended, defined by the kind of attacker it can resist: SL 1 protects against casual or coincidental violation, SL 4 against sophisticated attacks with extended resources and high motivation.
- OT security
- Standards
In one sentence
In IEC 62443, a security level (SL 0–4) states which kind of attacker a zone, conduit or component is designed to resist.
Example
A controller zone is specified at SL 2, protection against intentional violation using simple means with low resources, generic skills and low motivation.
Explained in context
Context cards connect this term with others to answer one question. Also in British English and German.
How it applies
- Engineering: SL 2 addresses intentional violation with simple means, low resources, generic skills and low motivation; SL 3 addresses sophisticated means with moderate resources, IACS-specific skills and moderate motivation; SL 4 extends this to extended resources and high motivation. Higher levels require more requirement enhancements under each foundational requirement.
- Types: IEC 62443 distinguishes target (SL-T), capability (SL-C) and achieved (SL-A) security levels.
- Compliance: Stating a security level is a claim that must be backed by evidence, for example an assessment against IEC 62443-3-3 or IEC 62443-4-2. A security level does not make a product compliant with the CRA or any other law by itself.
- Documentation: Always state which type of security level is meant, for which zone or component, and under which conditions. "Supports SL 2" in marketing text without these details is misleading.
Security level vs. safety integrity level
A Safety Integrity Level (SIL) expresses the required risk reduction of a safety function against random and systematic failures. A security level expresses resistance against attackers. The numbers are not comparable, and a high SIL says nothing about security.