Defence Efficiency

In order to automate actions, such as defences against network attacks, one needs to quantify their efficiency. This can subsequently be used in post-evaluation, learning, etc. In order to quantify the defence efficiency as a function of the impact of the defence and its total cost, we present several natural requirements from such a definition of efficiency and provide a natural definition that complies with these requirements. Next, we precisely characterize our definition of efficiency by the axiomatic approach; namely, we strengthen the original requirements from such a definition and prove that the given definition is the unique definition that satisfies those requirements. Finally, we generalize the definition to the case of any number of input variables in two natural ways, and compare these generalizations.