Understanding the Principle of Least Functionality in the CM Domain

TheConfiguration Management (CM) domainin CMMC 2.0 focuses on maintaining the security and integrity of an organization’s systems through controlled configurations and restrictions on system capabilities.

The principle ofLeast Functionalityrefers to limiting a system’s features, services, and applications to only those necessary for its intended purpose. This principle reduces the attack surface by minimizing unnecessary components that could be exploited by attackers.

Justification for the Correct Answer: Least Functionality (C)

CMMC Practice CM.L2-3.4.6 (Use Least Functionality)explicitly states:

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

Thegoalis to prevent unauthorized or unnecessary applications, services, and ports from running on the system.

Examples of Implementation:

Disabling unnecessary services, such as remote desktop access if not required.

Restricting software installation to approved applications.

Blocking unused network ports and protocols.

Why Other Options Are Incorrect

A. Least Privilege

This principle (associated with Access Control) ensures that users and processes have only the minimum level of access necessary to perform their jobs.

It is relevant to CMMC PracticeAC.L2-3.1.5 (Least Privilege)but does not define system capabilities.

B. Essential Concern

There is no officially recognized cybersecurity principle called " Essential Concern " in CMMC, NIST, or related frameworks.

D. Separation of Duties

This principle (covered under CMMCAC.L2-3.1.4) ensures that no single individual has unchecked control over critical functions, reducing the risk of fraud or abuse.

While important for security, it does not define essential system capabilities.

Official CMMC and NIST References

CMMC 2.0 Level 2 Assessment Guide – Configuration Management (CM) Domain

CM.L2-3.4.6 mandatesleast functionalityto enhance security by removing unnecessary features.

NIST SP 800-171 (which CMMC is based on) – Requirement 3.4.6

States: " Limit system functionality to only the essential capabilities required for organizational missions or business functions. "

NIST SP 800-53 – Control CM-7 (Least Functionality)

Provides detailed recommendations on configuring systems to operate with only necessary features.

Conclusion

Theprinciple of Least Functionality (C)is the basis for defining essential system capabilities in theConfiguration Management (CM) domainof CMMC 2.0. By applying this principle, organizations reduce security risks by ensuring that only the necessary functions, services, and applications are enabled.