CM.L2-3.4.6 Least Functionality

Employ the principle of least functionality by configuring organizational systems to provide only essential capabilities.

Source: NIST SP 800-171 Rev 2 3.4.6

Discussion: Systems can provide a wide variety of functions and services. Some of the functions and services routinely provided by default, may not be necessary to support essential organizational missions, functions, or operations. It is sometimes convenient to provide multiple services from single system components. However, doing so increases risk over limiting the services provided by any one component. Where feasible, organizations limit component functionality to a single function per component. Organizations review functions and services provided by systems or components of systems, to determine which functions and services are candidates for elimination. Organizations disable unused or unnecessary physical and logical ports and protocols to prevent unauthorized connection of devices, transfer of information, and tunneling. Organizations can utilize network scanning tools, intrusion detection and prevention systems, and end-point protections such as firewalls and host-based intrusion detection systems to identify and prevent the use of prohibited functions, ports, protocols, and services.

Assessment Objectives:

Determine if:

Examine: [SELECT FROM: Configuration management policy; configuration management plan; procedures addressing least functionality in the system; security plan; system design documentation; system configuration settings and associated documentation; security configuration checklists; other relevant documents or records].

Interview: [SELECT FROM: Personnel with security configuration management responsibilities; personnel with information security responsibilities; system or network administrators].

Test: [SELECT FROM: Organizational processes prohibiting or restricting functions, ports, protocols, or services; mechanisms implementing restrictions or prohibition of functions, ports, protocols, or services].

SPRS Score: 5

POA&M Allowed: No