The research employs an adaptive cross-disciplinary research strategy in an industrial example to address port facilities’ inability to assess whether their security systems are efficient. The research combines a twin-pronged approach of first, adapting Markowitz (1952) theory of portfolio selection from the field of finance to maritime port security to examine each port facility’s security systems as a portfolio; and secondly, through portfolio optimization to construct the optimum theoretical portfolio of security systems drawn from a number of different port facilities owned by Dubai Ports World. The research builds on the existing literature and proposes new definitions of security, port security, port security risk and port security risk management. The research also develops a model of port security risk based on Willis et al’s (2005) definition of terrorist risk. Furthermore, the research builds on the work of Gleason (1980) and examines terrorist attacks on ports and on shipping in ports between 1968 and 2007 and shows, using the Kolmogorov-Smirnov test, that they follow a Poisson distribution. The contribution which the research makes is in terms of adapting Markowitz (1952) theory to the port security environment; and the modelling and measurement of the impact of the introduction of new port security technology, changes in background port security threat levels and for the planning of port security in Greenfield sites. Furthermore, the adaptive approach of the research is generalisable to all nodes in the supply chain and is not limited to port facilities alone