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IBM reveals that hackers defeat smart card security by repeatedly entering
the PIN and analysing variations in the current drawn by the card’s processor
chip as it checks the number (EP 973 134). IBM is planning a smart card with a
built-in counter that logs the number of PIN code entries, and blocks access to
the card after a set number of tries. In cards that are used frequently, such as
the ones that let you withdraw cash or get through a turnstile, the counter
resets itself to zero every time the card is successfully used.