A detector for detecting a possible transmission of data according to an embodiment of the present invention includes a receiver adapted to the determine a spectral density in the frequency range of an electromagnetic spectrum and an evaluating circuit coupled to the receiver and adapted to determine an effective channel capacity based on the determined spectral density. The evaluating circuit is further adapted to compare the determined effective channel capacity with a threshold value and adapted to generate an evaluation signal indicating a possible presence of the transmission of data based on a result of the comparison.