Network Defense Essentials (NDE) Practice Exam 2025 - Free Network Defense Practice Questions and Study Guide

The correct answer is preventative controls, which are designed to stop unauthorized access to restricted areas before it occurs. In the context of John attempting to enter the second floor of a building where access is restricted, preventative controls would include measures like locked doors, barriers, or security personnel that actively prevent him from gaining entry.

These controls aim to eliminate risks by thwarting actions that could lead to security breaches. By restricting physical access to areas deemed sensitive or confidential, preventative controls serve their fundamental purpose of protecting assets and personnel.

In contrast, deterrent controls are intended to discourage unauthorized behavior but do not actively prevent access, while detective controls are designed to identify or detect breaches after they have occurred, and compensating controls serve as alternative measures when primary controls are not feasible. Therefore, in this situation, preventative controls are specifically what kept John from entering the restricted area.