The system includes an intercepting booth (1) and at least two detecting units (2) and (3), of which the first one analyzes the variation over time of the weight of people or things penetrated into the booth, the second one analyzes the variation over time of the capacity of the electrical capacitor consisting of two metal armors (4) and (5) between which the controlled passage into the booth (1) is comprised. It further includes an electronic programmed processing unit (8) the inputs (9) of which are connected to at least the two detecting units (2) and (3) and the outputs (10) of which are connected to at least one alarm unit (11) and the elements for locking at least the door (13), of the booth (1) that separates the controlled passage (6) from the protected area (14).