Methods and devices are provided for use in detecting relay attacks between devices in a communications network. One method includes sending first data by a first device to a second device, and receiving, by the first device, a communication from the second device where the communication comprises second data generated at the second device and a time parameter related to the generation of the second data. The method also includes measuring a total transmission time at the first device between sending the first data and receiving the communication, and determining a further time parameter related to the generation of the second data based at least in part on the measured total transmission time. The method then further includes determining the presence of a relay attack between the first and second devices in dependence on a comparison of the time parameter and the further time parameter.