Any item in the RFID system can be compromised if a visitor wraps the pro

tected material in ordinary household foil to block the radio signal. Bringing

household foil into a library using RFID would represent premeditated theft,

just as bringing a magnet into a library using EM technology would.

Another way to compromise an RFID system is by placing two items against

each another so one tag overlays another. That overlapping may cancel the

signals but requires knowledge of the technology and careful alignment.