03.04.06: Least Functionality

Beyond CMMC Level 1

The free web app covers the 17 CMMC Level 1 practices. This requirement is part of the full NIST 800-171 set — get the desktop app to work on all 110 requirements with SPRS scoring. Previously saved data is shown read-only below, and your data always remains exportable in full.

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Security Requirements for 03.04.06 Least Functionality

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 GuidanceExamine 0/8

How an assessor determines this requirement is met. Source: CMMC Assessment Guide – Level 2, Version 2.13 (NIST SP 800-171 Rev. 2).

Discussion

You should customize organizational systems to remove non-essential applications and disable unnecessary services. Systems come with many unnecessary applications and settings enabled by default including unused ports and protocols. Leave only the fewest capabilities necessary for the systems to operate effectively.

Examples

Example 1
You have ordered a new server, which has arrived with a number of free utilities installed in addition to the operating system. Before you deploy the server, you research the utilities to determine which ones can be eliminated without impacting functionality. You remove the unneeded software, then move on to disable unused ports and services. The server that enters production therefore has only the essential capabilities enabled for the system to function in its role [a, b].

Assessment Methods

Examine

The process of reviewing, inspecting, observing, studying, or analyzing assessment objects (e.g., policies, procedures, plans, system designs, mechanisms) to facilitate understanding, achieve clarification, or obtain evidence.Example: An assessor reads the access control policy and inspects system configuration settings to confirm they match.

Not all of the evidence listed is required to meet this requirement — check the items your organization has collected.

Configuration management policy
Configuration management plan
Procedures addressing least functionality in the system
System security plan
System design documentation
System configuration settings and associated documentation
Security configuration checklists
Other relevant documents or records

Interview

The process of holding discussions with individuals or groups within an organization to facilitate understanding, achieve clarification, or identify the location of evidence.Example: An assessor asks a system administrator to describe how user accounts are approved, reviewed, and disabled.

Personnel with security configuration management responsibilities
Personnel with information security responsibilities
System or network administrators

Test

The process of exercising assessment objects (e.g., activities, mechanisms) under specified conditions to compare actual behavior with expected behavior.Example: An assessor attempts to sign in with a disabled account to confirm that access is denied.

Organizational processes prohibiting or restricting functions, ports, protocols, or services
Mechanisms implementing restrictions or prohibition of functions, ports, protocols, or services

Potential Assessment Considerations

Are the roles and functions for each system identified along with the software and services required to perform those functions [a]?
Are the software and services required for those defined functions identified [a]?
Is the information system configured to exclude any function not needed in the operational environment [b]?

Key References

NIST SP 800-171 Rev. 2 3.4.6

Overview