Card cloning is a problem. Not just for work ID cards but also for personal credit cards.

I bet you’ve seen these “RFID blockers” off Scamaz… Amazon and wonder if they work. In this photo are two types; a professional type designed to meet specific standards and the bottom one which is the Scama… Amazon special. Shove it in your wallet, purse, etc and it’ll apparently block card cloning / contactless transaction attacks.

They both work, although I would always test the one off Amazon if you get them. I have so far been through four of these and all of them have blocked me from copying a card. I have tested against the Flipper Zero, mobile phone NFC, the iCopy-X and a Proxmark 3. I have tried multiple different types of card, including my old credit card.

These don’t work by blocking the radio frequency, but by sinking energy away from the target card to prevent enough RF energy being available to fully energise the chip. As a result, they don’t need to be in between the source and the card, just within the field. I’ve found they work around 2” either side of the target card. The interior appears to be a simple NFC card with a coil and a black blob for a chip. I assume it’s configured to absorb as much RF energy as possible.

If you have been wondering about getting these, I’d definitely test them using a phone with NFC and an NFC tools application, but all the ones I’ve tested work. You can also fold up some foil and place it in your wallet and see if that works for you as well.

And for those who think card clash will save you; it won’t always. Modern techniques can overcome this and discriminate between the data coming off multiple cards in the same field.