What is the first layer of defense in physical and environmental security?

• A. Implement encryption at rest
• B. Assess the perimeter
• C. Configure firewalls
• D. Install intrusion detection systems

Answer: (B)

In physical and environmental security, defense starts at the outer boundary. Assessing the perimeter establishes the first line of defense by identifying where entry could occur and whether barriers, gates, lighting, cameras, sensors, and patrols provide effective deterrence and early warning. This outer boundary review sets the foundation for all subsequent layers of protection, such as controlled access, monitoring, and environmental safeguards.

Encrypting data at rest addresses information protection rather than preventing physical entry. Configuring firewalls and installing intrusion detection systems pertain to network security and monitoring once a systems boundary is breached or as part of digital defenses—not the initial physical barrier.