Dutch security researchers rode the London Underground free for a day after easily using an ordinary laptop to clone the "smartcards" commuters use to pay fares, a hack that highlights a serious security flaw because similar cards provide access to thousands of government offices, hospitals and schools... The hackers scanned one of the Underground's many card readers to collect the cryptographic key that purportedly keeps the system secure. The keys were uploaded to a laptop, essentially turning them into portable card readers. The hackers then brushed up against passengers to wirelessly upload the information on their Oyster cars. That information in hand, it was a simple matter of using it to program new cards.