A security control for an information system that has not been designated as a common security control or the portion of a hybrid control that is to be implemented within an information system…

A System-Specific Security Control is implemented directly within an information system and its environment of operation, and it is the sole responsibility of that specific system to implement and maintain it. It is distinct from common controls, which are inherited from an organization-wide service, or the inherited part of a hybrid control.

Hybrid Security Controls are those where some aspects are implemented as common controls and others are system-specific, so it's a mix, not exclusively the portion implemented within an information system.

Network Security Controls are a category of security controls focused on network protection, not a classification based on their implementation scope (system-specific vs. common).

Security Control Inheritance refers to the mechanism by which an information system receives common security controls from an organizational system or external provider, not the type of control implemented locally.