System which comprises a plurality of devices for acquiring (1) identifiers of transmitter devices (2) by means of radio frequency in the 2.4 GHz band, these acquisition devices (1) being connected to a central management computer (3) for sending the captured identifiers of the transmitter devices (2) in form of tags (32) in order to include the latter in a database (31). The method comprises the stages of: —acquiring the identifier of the transmitter devices (2) at particular points; —extracting the exclusive part; —encrypting said exclusive part in a tag (32); —sending the tag (32), acquisition point and time (33) to a database (31) of a central computer (3); —comparing the tag (32) and time (33) with the previously stored data in the database (31).