This technique is called "bump cloning" because all that the adversary would have to do is "bump" you in a hallway or elevator to copy your card, even if it remains in your wallet. This would for all intents and purposes make his device a "clone" of your card, useable in any reader in the system!
A most worrying aspect of this device is the target person has no idea his card was "cloned" and therefore would have no reason to report it as being compromised. Additionally, if any mischief was done then the card access system would dutifully report the target's card number was used to access the space.
Wiegand and MiFare proximity card systems are apparently immune to this type of attack.
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