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Application & OT Security · Advanced

IEC 62443 Security Levels (SL)

Four security levels in IEC 62443 describing the capability required to protect against increasingly capable attackers.

Definition

SL 1 protects against casual or coincidental violation; SL 2 against intentional attack with simple means, low resources and generic skills; SL 3 against sophisticated means with moderate resources and IACS-specific skills; SL 4 against sophisticated means with extended resources (nation-state level). The standard distinguishes target (SL-T), capability (SL-C) and achieved (SL-A) levels.

Example

A risk assessment sets SL-T 3 for the safety system zone and SL-T 2 for the HMI zone.

Exam tip

Match the attacker description to the SL; SL-T vs SL-C vs SL-A is a common question.

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