CMMC Practice PE.2.135
Protect and monitor the physical facility and support infrastructure for organizational systems.
Bold Coast Security Guidance
"Protect and monitor" can mean a lot of things! Typically, an organization will need to deploy cameras to monitor ingress/egress points in the facility, and also critical areas within the facility. This video should be able to record video for up to a month or longer, as determined by a risk assessment.
Protecting and monitoring the physical infrastructure extends to environmental controls, such as proper HVAC, fire suppression, water sensors, and monitoring of these systems.
The guidance and clarification provided by CMMC also point out the need to protect network cabling using conduits, and disconnecting or protecting unused network ports.
Larger organizations may need to consider security guards for video and ingress/egress monitoring, and active network monitoring for unauthorized devices on your network and wiretap sensors.
DRAFT NIST SP 800-171 R2
Monitoring of physical access includes publicly accessible areas within organizational facilities. This can be accomplished, for example, by the employment of guards; the use of sensor devices; or the use of video surveillance equipment such as cameras.
Examples of support infrastructure include system distribution, transmission, and power lines. Security controls applied to the support infrastructure prevent accidental damage, disruption, and physical tampering. Such controls may also be necessary to prevent eavesdropping or modification of unencrypted transmissions. Physical access controls to support infrastructure include locked wiring closets; disconnected or locked spare jacks; protection of cabling by conduit or cable trays; and wiretapping sensors.