Train detection security system and method for detecting a moving train are provided. The train detection security system includes one or more sensor units fixed to a rail of a rail track. The sensor units are arranged for detecting a first signal induced by a moving train and propagated through the rail. The system further includes a control unit including a signal processor arranged for receiving first sensor output signals representing the first signals from each of the one or more sensor units, processing the first sensor output signals and generating a train warning signal representing characteristics of the moving train based on envelope characteristics of the first sensor output signals.