CM.L2-3.4.6 Least Functionality

CMMC Practice CM.L2-3.4.6 – Least Functionality: Employ the principle of least functionality by configuring organizational systems to provide only essential capabilities.

Links to Publicly Available Resources

Discussion [NIST SP 800-171 R2]
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.

Further 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.