Which of the following is true about physical I/O ports?

Securing only the necessary physical ports is a prudent approach to maintaining a secure environment in critical infrastructure. This principle aligns with the risk management framework that is central to NERC Critical Infrastructure Protection standards. By focusing on essential ports, organizations can allocate resources more efficiently, ensuring that security measures are applied where they are most effective and necessary, thus minimizing potential vulnerabilities while avoiding unnecessary security expenditures on lesser-used ports.

Furthermore, this strategy recognizes that some ports may serve limited or no purpose within the operational environment. Securing only those ports that are actively in use or that could potentially pose a risk of unauthorized access or data breaches helps to streamline security efforts and ensure that robust protections are in place for the most critical access points.

This approach also aligns with the concept of defense in depth, where multiple layers of security control are implemented based on the specific needs of the infrastructure. This selective security measure thus fosters a balanced and effective security posture, addressing potential risks while considering the operational requirements.