Techniques developed to enhance the efficiency of physical surveillance on target individuals. During the Cold War, considerable research was undertaken to create chemical and other formulas that would serve to identify a quarry, sometimes known as a “rabbit,” even when the person’s appearance had been altered, by alerting watchers when the target passed through a channel or choke point, or that would enable tracking to occur from a distance safe enough not to compromise the surveillance. The East Germans experimented with substances that could be sprayed onto the shoes or clothes of a target to increase the scent available for specially trained dogs, while the KGB was known to have applied potentially dangerous toxins onto targets to aid detection by electromechanical devices.
The use of potentially hazardous “spy dust” deployed in Moscow against selected Americans diplomats prompted a diplomatic protest in August 1985.
According to information supplied by a defector, Vitali Yurchenko, the KGB also experimented with insect pheromones, which caused a box of male insects to react when someone sprayed with female pheromones passed nearby.
Documents have also been the subject of tagging. For example, British Admiralty papers have been irradiated to enable sensors to monitor their removal from secure areas.