Recently, relay attacks has renewed interest, not least because of the rise of NFC applications in smartphones. In the context of the NFC ecosystem, relay attacks allow an attacker to lull an NFC reader by making it believe that the legitimate user is in its vicinity. The idea of such attacks is simple: forwarding the NFC commands intended for the Secure Element (SE) inside the closest smartphone to another far away SE. The invention relates to a method of detecting relay attacks. Unlike existing solutions based on distance bounding, our invention is based on the Trusted Execution Environment (TEE) that runs inside the smartphone. In our invention, we define specific mechanisms allowing TEE to verify whether a particular NFC response has been indeed computed by the Secure Element of the bounded smartphone. In addition, we enhance the TEE features by giving it control over the NFC communication, so that it can block NFC responses from being sent to the NFC reader. Thus, we prevent relay attacks by making the TEE blocking any NFC response that was not produced by the SE running inside its bounded mobile device.