Which of the following best defines the measures used to protect personnel, equipment, and documents from unauthorized access and threats like theft or terrorism: physical security, critical infrastru

The definition provided describes the core aspects of physical security.

• Physical security involves the use of security measures to protect personnel, equipment, material, and documents from unauthorized access, damage, theft, espionage, sabotage, and terrorism. This includes measures like access control, surveillance, alarms, and security personnel.

Let's look at the options:

• physical security: This aligns perfectly with the description of preventing unauthorized access and safeguarding against various threats to physical assets and personnel.
• critical infrastructure protection: This is a broader concept focused on protecting essential systems and assets, which may include physical security but is not solely defined by the measures listed.
• antiterrorism: This focuses specifically on defensive measures against terrorist acts, which is a part of the given definition but not the entire scope.
• force protection: This is a military term encompassing all measures to protect personnel, resources, and facilities, which is broader than the specific security measures described.

Therefore, the most accurate definition is physical security.

The final answer is $\text{physical security.}$