1. A method of deriving first order logic language rules for use in analysing new data to identify anomalies in the new data, the method comprising: formatting historical data to be in a form suitable for application of a machine-learning algorithm thereto; applying the machine-learning algorithm to said formatted historical data to generate a set of first order logic language rules that cover said formatted historical data; and, analysing said set of first order logic language rules to obtain a subset of said set of first order logic language rules which can be used as first order logic language rules in analysing new data.