Abstract: A User Equipment, UE, (120), a network node (110, 111, 140) and methods therein, for detection that the UE has been communicating with a non-legitimate device (150) which impersonates a network node of a legitimate network. In this method, the UE or the network node obtains information regarding technical details of the transmission of a service received by the UE, wherein the information comprises a generation of the RAT/mobile network used for the transmission. The UE then provides the technical details to a user of the UE and/or to an application on the UE. The network node is also able to determine that the service was received from the non-legitimate device when the technical details do not correspond to the technical details expected for the legitimate network.