Date of Award


Degree Type


Degree Name

Master of Science (Security Science)


School of Computer and Security Science


Computing, Health and Science

First Advisor

Dr David Brooks


As a quantitative auditing tool for Physical Protection Systems (PPS) the Estimated Adversary Sequence Interruption (EASI) model has been available for many years. Nevertheless, once a systems macro-state measure has been commissioned (Pi) against its defined threat using EASI, there must be a means of articulating its continued efficacy (steady state) or its degradation over time. The purpose of this multi-phase study was to develop the concept and define the term entropic security decay. Phase one presented documentary benchmarks for security decay. This phase was broken into three stages; stage one presented General Systems Theory (GST) as a systems benchmark for the study. Stage two applied the writings from stage one to physical security, and stage three presented a benchmark for considering physical system decay. Phase two incorporated the pilot study towards validating the feasibility of undertaking the main study and refining interview instrumentation. Phase three executed the main study, extracting and presenting security experts (N=6) thoughts, feelings and experiences with the phenomenon of security decay. Phase four provided the interpretative analysis, responding to the study’s research question.