It's known that card readers, which use the Wiegand format, can be attacked by installing a sniffer, such as an ESPKey. After the sniffer is installed, whenever anyone uses the reader, their credentials get saved, and the attacker can clone them.
What is the defense against this? The article mentions that card readers have a tamper sensor. Is a correctly installed tamper sensor enough to thwart this attack? What exactly does the tamper sensor do, and what happens when it's set off?
Also, since ESPKey attacks specifically target the interceptable wiegand protocol, is there some other protocol which provides secure communications? Many articles cite Wiegand as being the most common protocol. What percentage of card readers are vulnerable to this attack, and what's the next most common non-vulnerable protocol?