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The RFID sniffer is a simple analog electronic circuit which can detect the presence of 13.56 MHz RFID tags. These tags are commonly used in all kinds of plastic cards like access badges, bank cards, library cards, loyalty cards and so on. Also many other objects may carry RFID tags without you knowing it. Books, toys, and even clothing might be tagged. Carrying tagged objects with you can reveal your identity or whereabouts to anyone equipped with the appropiate tools to read RFID tags.