A device and method for the unambiguous identification of Wi-Fi devices is disclosed, by receiving probe request frames sent by Wi-Fi devices, extracting a set of features from a plurality of fields of each probe request frame, assigning a footprint to each probe request frame based on the extracted set of features, for each footprint, performing a cluster analysis on a time series of the sequence numbers included in the header of the probe request frames associated with the corresponding footprint, obtaining at least one cluster per footprint, identifying a Wi-Fi device for each different cluster, which identifies Wi-Fi devices that are not connected to a Wi-Fi network and employ MAC address randomization.