A method of and arrangement for detecting a manipulated or defect base station of a communication network is disclosed, wherein a target base station, having selected one or more algorithms on the basis of a prioritized algorithm list (PAL) and a UE security capabilities (SCAP), reports UE SCAP related information to a core network node. The core network node having knowledge of the UE SCAP compares this information or parts of this information with the retrieved UE SCAP related information in order to be able to identify a manipulated or defect base station when a comparison fails to match.