In addition to threats of passive eavesdropping and tracking, an infrastructure dependent on RFID tags may be susceptible to denial of service attacks or tag spoofing. By spoofing valid tags, a thief could fool automated checkout or security systems into thinking a product was still on a shelf. Alternatively, a thief could rewrite or replace tags on expensive items with spoofed data from cheaper items. Saboteurs could disrupt supply chains by disabling or corrupting a large batch of tags.