An effective and real-time technique called "Detection-Prevention-Geolocation (DPG)" system is developed to provide capabilities of detection, prevention and location for a satellite monitoring system (SMS). The proposed mechanism mainly includes three functions: detection, prevention and location. In detection component, to provide the video sequence authentication, the authorized code including time stamp, copyright number and secret code are used as watermark to be embedded into the video sequence of MPEG-2 streams. Then the watermarked signals are transmitted through the transponder of satellite and relayed to the receiver of monitoring station. Thus, the monitoring station can detect the watermark signal from watermarked signals to authenticate the video contents. Should the watermarked signal has no authorized right, the illegal use will be easily detected by the watermarking algorithm, and thus the SMS makes a control signal to suspend the transponder operation for limiting the illegal content to broadcast for the public broadcasting network. Meanwhile, the geolocater will be driven to locate the source of deliberate interference. The bearing of terrestrial satellite, therefore, can be determined using the position technique such as Twiddle-Satellite-Location method. Consequently, the DPG system can provide the defense ability for the satellite monitoring system.