A device built by legendary hacker Samy Kamkar calls into question the security of payment cards as the U.S. continues to grapples with card fraud.

Kamkar’s device, nicknamed MagSpoof, is about the size of a U.S. quarter, and it’s safe to say it would be a fraudster’s dream.

MagSpoof can predict what a new American Express card number will be based on a canceled card’s number. The new expiration date can also be predicted based on when the replacement card was requested.

It can also trick point-of-sale readers into accepting payment from cards that are supposed to have a microchip with advanced cryptographic capabilities designed to deter fraud, a system known as chip-and-PIN, but do not.

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