What method of security involves actively preventing intrusions?

The concept of actively preventing intrusions is best captured by the method known as denial. Denial focuses on restricting access and preventing unauthorized individuals or entities from entering a secured area or gaining access to sensitive information. This approach is essential in security operations, as it establishes barriers that render intrusion attempts ineffective from the outset.

In operational contexts, denial can entail physical barriers such as fences and gates, as well as technological solutions like access control systems and alarm mechanisms. The primary goal is to create an environment where intrusions are thwarted before they can occur, effectively maintaining a strong security posture.

Other methods mentioned, such as delay, detect, and deter, serve different functions within a comprehensive security strategy. While delay involves slowing down an intruder's actions to allow time for a response, detect focuses on identifying intrusions after they happen. Deter aims to discourage potential intruders through visible security measures or the perception of high risk, rather than preventing access entirely. Thus, denial is the most direct approach to actively preventing intrusions.