That part of security concerned with physical measures designed to safeguard personnel; to prevent unauthorized access to equipment, installations, material, and documents; and to safeguard them against espionage, sabotage, damage, and theft. (JP 1-02 and JP 3-0).
The security discipline concerned with physical measures designed to: protect personnel; prevent unauthorized access to facilities, equipment, material, and documents; and defend against espionage, terrorism, sabotage, damage, and theft. (IC Standard 700-1, 4 Apr 2008).
Source: Terms & Definitions of Interest for DoD Counterintelligence Professionals, Office of the National Counterintelligence, https://www.dni.gov/files/NCSC/documents/ci/CI_Glossary.pdf