MasterCard uses “PayPass” to identify the cards. Chase bank coined the term “Blink.” Some contactless cards, which use a radio frequency identification, or RFID, chip, might simply have a symbol on the card consisting of four curved lines. Others may not have a symbol at all.
The cards are touted as convenient, but they are also vulnerable to being skimmed without ever leaving your pocket. The information communicated from your card to a card reader can be enough to create a counterfeit card that can be successfully used to make an unauthorized purchase.
All passports issued since 2004 are equipped with an RFID computer chip, which may be scanned to obtain your bio-metric data.
RFID wallets and products "block" unwanted scans, and keep your information safe.