Method of protection of information against laser microphones

Abstract

The current level of development of spy devices make it possible to listen a conversations inside of a room that has a window without ever getting near the room. Devices that allow listening are called laser microphones or Laser Based Listening System (LBLS). There are several common methods of protection against this type of threat, but they all have drawbacks. We proposed a method of laser counteraction as an alternative to existing ones, and presented the concept of its implementation. This method is based on the process of "mixing" the probing laser beam of the attacker with opposing radiation, which will considerably complicate the process of receiving and extracting an informative signal on the receiving side of the laser microphone.