An RFID card uses read-only technology, making it useful in applications such as secure door access cards. NFC cards use more advanced two-way communications technology, making them suited to transactions such as payment authorisation. Both RFID and NFC cards use a small antenna to receive and transmit electromagnetic pulses so that communication is possible without physical contact.
For this reason I have avoided NFC contactless payment cards like the plague. There have been stories about portable readers being used to transact with or snatch data from contactless cards, and the antenna circuit in a contactless payment card allows it to be read through the fabric of a wallet or pocket, which means that such data snatching could occur without the card owner even realising it.
On top of the risk of theft from NFC cards, there is a lot of concern about the privacy risk that RFID cards present: if your RFID card can be automatically scanned without your knowing, then your location could be tracked throughout the day, whenever you carry such cards.
Most people could not care less about the security of their personal data: they'd happily walk around with their name, home address, and bank details pinned to their back in large script if someone offered them a dollar to do it. But if you're of a more cautious type, there is a solution: put your NFC and RFID cards into a tin foil hat (okay, the technical name is a Faraday cage).
By enveloping something in a conductive material you make it harder for external electromagnetic fields to reach it. Wrap an RFID or NFC card in a suitable material and you make it unlikely that a card reader will be able to detect and read from that card successfully.
You can probably make your own such shield from a bit of tin foil, adhesive tape and a finishing material of your choosing, if you have skill and/or patience. I have neither, so I opted to buy something ready made and settled on the OPTEXX RFID Blocking ID Etui Holder Nick Black Nappa. (Even though it has one of the least wieldy product names I've ever had to write into an online review.)
The OPTEXX RFID Blocking ID Etui Holder Nick Black Nappa is a leather card wallet with two covered card slots and one transparent card slot suited to photo ID cards, and it folds closed to keep these slots contained within. The slots are all perfectly sized to take a card with the dimensions of a standard debit or credit card. Folded closed, the RFID Blocking ID Etui Holder is slender and light, but has a reassuringly solid feel to it.
Removing a card from the top covered slot is easy enough, because about a centimetre of the card sticks out of the end of the top pocket. Removing a card from the lower covered slot is a little harder because the lower pocket easily accommodates the entire length of the card and you have to work to get your finger under the card to extract it.
According to the manufacturer's marketing literature (some of which uses an image of a man dressed as either an uncomfortable identity thief or a nervous ninja) the wallet protects cards of numerous types which use the following frequencies:
I tested the shielding capabilities using an NFC contactless payment card and a TfL Oyster card, both of which use the 13.56MHz frequency for communication. Below are my findings after numerous sessions of rubbing the wallet all around various card readers. (Apologies if you were in a queue behind me at any of these times.)
So I'm satisfied that, with the wallet folded shut, NFC cards are protected from being read if they're in the covered card slots. (I've not yet tested shielding of cards in the photo card slot. I'll update this page if I find a chance to do so.)
The OPTEXX RFID Blocking ID Etui Holder Nick Black Nappa is compact, light, and effective at protecting NFC cards from unexpected use. It's good enough that even I'm happy to carry a contactless payment card, when I never would have before. Just bear in mind that it won't suit you if you're the sort of person who doesn't want to have to take the card out of the wallet to use it.