Which of the following is NOT one of the three principles of cyber defense?

The principle that is recognized as NOT being one of the three key principles of cyber defense is the concept of maximal accessibility. In cybersecurity, the primary focus is on protecting information and resources rather than ensuring that they are maximally accessible.

The principle of least privilege involves limiting user access rights to the minimum necessary to perform their tasks, thereby reducing potential vulnerabilities. Defense in depth is a strategic approach that employs multiple layers of security controls to protect information and resources, ensuring that if one measure fails, others will still provide protection. Vigilance emphasizes the need for continuous monitoring and assessment to identify and respond to threats proactively. In contrast, maximal accessibility could lead to increased risk and exposure to cyber threats, undermining the overall security posture. Thus, while accessibility is important, it is not foundational in the context of cyber defense principles.