The example of a mixed economy company has a land development fraud neglected by the literature: there is widespread fraud, little by little, the top-down by imitation and addiction, in collusion implied. Literature was more interested, in fact, illegal maneuvers in the eyes of the officer or prohibited by law. But she had not modeled the process by which fraud is formed, grows and finds an end. Based on the case of the SEM, we propose a model for the dissemination of fraud and we discuss its possible generalization, while analyzing the appropriateness of traditional measures of fight against fraud.