ISA 62443-4-2:2018

hs ISA99 document in the ISA-62443 series provides detailed technical control system component requirements (CRs) associated with the seven foundational requirements (FRs) described in ISA-62443-1-1 including defining the requirements for control system capability security levels and their components, SL C(component).
As defined in ISA-62443-1-1 there are a total of seven Foundational Requirements (FRs):
Identification and authentication control (IAC),
Use control (UC),
System integrity (SI),
Data confidentiality (DC),
Restricted data flow (RDF),
Timely response to events (TRE), and
Resource availability (RA).
These seven FRs are the foundation for defining control system security capability levels. Defining security capability levels for the control system component is the goal and objective of this document as opposed to SL T or achieved SLs (SL A), which are out of scope.