Electric fence security device

The security device according to the invention comprises a ribbon electrical network (1) electrically connected to an electronic control device (2) which produces an output signal in the event of a fault in the electrical network (1). The electrical network is formed of two elementary electrical wires (4, 5) insulated from each other by an insulating means and assembled together with a composite wire (6) itself sheathed. The composite yarn (6) is for example arranged in a back-and-forth arrangement with parallel strands of the weaving type on warp threads or strips (7), with elementary intermediate interstices (8) of small size. The electronic control device (2) detects the breakage of at least one of the elementary electrical wires (4, 5) and / or the mutual contact with each other. Such a safety device is particularly reliable, and is particularly difficult to inhibit or neutralize.