The invention relates to a security device for a cover device of a pipe and/or for a pipe, that can be used for producing pipelines having a series of further pipes welded to each other, wherein the cover device comprises a sleeve covering an inner wall of the pipe, and the security device is designed for generating an alarm signal, wherein the security device comprises a structure-borne sound detection device comprising a structure-borne sound sensor for detecting manipulation of the pipe. The invention further relates to a system for monitoring pipes having a plurality of security devices having a receiving station for receiving the security device signals, preferably repeatable by means of a repeater, and an electronic data processor designed for analyzing the signals and for out-putting an alarm signal.