In this article, published in the Journal of Loss Prevention in the Process Industries in October 2013, H.M. Leith and John Piper discuss how current and projected malevolent threats posed by insiders, outsiders, collusion, and system-induced threats can erode system performance in terms of shut downs, sabotage, production disruption, and contamination. The paper focuses on application of business-prudent controls and discusses how disparities in implementation of controls can exacerbate system vulnerabilities.