What caution is advised when using the vector approach to security levels?

When using the security level (SL) vector approach in ISA/IEC 62443, each Foundational Requirement (FR) can have its own SL-T value. However, these values must reflect the organization’s specific risk assessment outcomes, not generic or industry default values.

“SL vectors should be derived based on the asset owner’s own risk matrix and risk tolerance, ensuring that the security levels support operational needs and business requirements.”

— ISA/IEC 62443-3-2:2020, Clause 6.5.2 – SL-T Vector Selection

Misalignment could lead to over- or under-protection of critical zones or conduits.