The most critical and foundational consideration in any physical security plan is to first define the problem. This initial step involves a comprehensive risk assessment to understand the specific threats, vulnerabilities, and potential impacts on the assets being protected. Defining the problem sets the scope and objectives for the entire security strategy. All subsequent actions, such as identifying solutions, selecting technologies, and implementing them, are contingent upon a clear and accurate problem definition. Without this, any security measures applied would be arbitrary and likely ineffective.

A. Apply the technology: This is an implementation step that occurs only after a problem has been defined and a specific solution has been designed to address it.

B. Apply the solution: This is the implementation phase of the security plan. It is a subsequent action, not the initial overall consideration.

C. Identify the problem: While part of the initial process, "defining the problem" is more comprehensive. It includes not just identification but also analysis and scoping of the risks and requirements.

1. Garcia, M. L. (2008). The Design and Evaluation of Physical Protection Systems. Butterworth-Heinemann. In Chapter 2, "Systematic Approach to Physical Protection System Design," the process begins with "Determination of physical protection system objectives," which is fundamentally about defining the problem by characterizing the facility and identifying threats (pp. 15-17).

2. Uptime Institute. (2018). Tier Standard: Topology. The standard emphasizes that the entire data center design, including physical security, must be based on the owner's business objectives and risk tolerance. This initial requirements-gathering phase is equivalent to defining the problem the facility must solve (Section 2.0, "Basis of the Tiers").

3. National Institute of Standards and Technology (NIST). (2020). NIST Special Publication 800-53, Revision 5: Security and Privacy Controls for Information Systems and Organizations. The Risk Management Framework (RMF) described, which is a foundational model for security, begins with the "Prepare" step. This step is dedicated to carrying out essential activities at the organization and system levels to help manage security and privacy risks, which is synonymous with defining the problem space (Chapter 2, "The Framework," p. 13).