An increasing proportion of world voice, data and image communication is transmitted via communication satellites. These may easily be jammed; all that is needed is a powerful transmitter with which to beam a jamming message towards the satellite. This will overload its transmitter and thus effectively drown its signals in noise so long as the jamming transmission is maintained. Such quenching, effected from any one point on the earth's surface, could reach any satellite visible from that point. It is possible also to jam receivers in a region by transmitting noise on the channel used by satellites, a method that will not interfere with the satellite itself.