"Understand that contactless cards can be read through your pocket Security researcher and former fraudster Tony Sales demonstrated live on camera that a Flipper Zero NFC reader placed within about two centimetres of a pocket can silently pull a card number and expiration date in seconds. The narrator notes: "the same thing can be done with any old NFC-capable device" — meaning an attacker needs no special hardware. While the chip's secret key and the CVV are not exposed this way, limiting the damage, the US has no single-transaction cap on contactless payments, so a single ghost tap could cost thousands of dollars. Knowing this, keeping cards in a Faraday-cage wallet or simply moving them to a phone wallet eliminates the attack surface entirely. Source: Tony Sales & Derek Muller, Veritasium, How Your Credit Card Works — and How It's Being Hacked"