The interception of communication between the reader and the RFID tag is one of the most specific threats to contactless technology. Since the communication of commercially available tags takes place frequently either in the 125 kHz or 13.56 MHz range, interception is basically possible using simple means. Is is often argued that standard compliant RFID systems allow only distances between 10-15 cm or a maximum of 1.5 m as typical working distance. However, it is often forgotten that this only affects the active communication. The field strengths used in the standards referred to give rise to the presumption that the passive interception of communication is still possible at a distance of several meters.
The measurement set-up described in this article (PDF) (in German) was used to verify this assumption.