This paper deals with the issues raised in terms of fight against the mafia by the infiltration of legitimate businesses by Mafiosi. First, we identify the main features describing an economy with three sectors: the legal sector, the illegal one and the legal-criminal one. Therefore we can put forward the main distortions introduced by the Mafia in the way markets should work. Then we analyse the consequences that enfold in terms of measures to be adopted in order to crack down on this infiltration of legitimate businesses. In particular, we draw a comparison between the logic of flows (inspired by Becker and the costs-benefits analysis) and the patrimonial approach (which is exemplified in Italy by the Rognoni-La Torre law). This comparison makes clear why the specific phenomenon of infiltration cannot be dealt with properly thanks to the logic of flows approach and that measures such as the confiscation of patrimonies is a better way to deter the investments of Mafiosi in the legal economy.