Software based systems are ubiquitous in modern day operations. There has been an increase in software based system attacks; leading to the need to equip the project managers, software designers and software developers with better predictive attackability models at the architectural design stage. Attackability is a concept proposed recently in literature to measure the extent that a software system or service could be the target of a successful attack. The book refines the existing predictive metrics models by using the relationship between the internal software attributes: complexity, coupling and cohesion to predict at the architectural design level, an external software attribute, attackability. The model so generated, representing the technical aspect was combined with a social attackability model, to generate a holistic attackability model. The social attackability model is based on identified human traits that make people vulnerable to social engineering attacks. The traits considered are: distraction, social compliance, herd mentality, dishonesty, kindness, time pressure, and need/greed.