Which of the following is NOT considered a layer of security?

Layered security, often referred to as "defense in depth," is a principle that involves implementing multiple layers of security measures to protect assets and personnel effectively. The correct answer highlights that single-entry protocols do not constitute a standalone layer of security.

Single-entry protocols typically refer to a procedural measure that may govern how individuals gain access to a facility or area but do not embody a comprehensive security measure on their own. In contrast, physical barriers, surveillance systems, and community engagement all represent distinct and critical layers of security.

Physical barriers, such as fences or gates, create tangible boundaries that deter unauthorized access. Surveillance systems, including cameras and monitoring equipment, provide the ability to observe and respond to security incidents in real time. Community engagement involves building relationships with local groups to foster cooperation and awareness about security concerns, enhancing the overall security environment.

Thus, single-entry protocols, while important for access control, do not provide a multifaceted approach to security similar to the other options and therefore are not considered a distinct layer of security.