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Security Fundamentals & Crypto · Intermediate

Principle of Least Functionality

Configuring systems to provide only essential capabilities and disabling unneeded ports, protocols, and services.

Definition

Least functionality (NIST SP 800-53 control CM-7) restricts systems to the features required for their mission. It reduces attack surface and complexity. It applies to services, software installation, and peripheral use such as USB ports.

Example

A kiosk PC is configured to run only the browser in kiosk mode, with USB storage disabled.

Exam tip

Least privilege applies to rights; least functionality applies to system features and services.

Related terms