Relay Attack

A relay attack exploits the short-range radio communication used by contactless payment cards, NFC-enabled smartphones, and keyless entry systems (such as car key fobs). Two attackers work together: one stands close to the victim (in a queue, on public transport, or near their front door), while the other stands near the payment terminal or car door. Radio equipment carried by each attacker relays signals between the victim's card or key and the reader, effectively 'stretching' the legitimate communication channel over a much greater distance than intended.

For contactless payments, this allows a fraudster to make a transaction at a POS terminal while the genuine cardholder and their card are in a completely different location. For keyless car theft, it tricks the car into thinking the key fob is nearby and unlocks the doors and allows the engine to start.

Countermeasures include using RFID-blocking wallets or card sleeves that prevent the card from being read when not in use, storing car keys in signal-blocking pouches at home, contactless payment limits enforced by card issuers, and transaction authentication requirements (such as PIN entry above certain amounts). Ultra-wideband (UWB) technology is increasingly used in newer keyless systems to measure distance precisely and defeat relay attacks.