The presumption is that most technical attacks encountered by those on the non-Federal level will be relatively unsophisticated and hence more susceptible to detection or nullification. Technical audio surveillance techniques and audio attack methods include mechanical attacks, visual/optical attacks, microphone and wire devices, free space transmitters, carrier current transmitters, and telephones. The unaided human ear is perhaps one of the most important devices used in violations of audio security; its effectiveness may be enhanced by the use of a stethoscope against an adjoining wall. Other mechanical attack devices include tape recorders, which can be disguised in various sizes and shapes. Telescopes, binoculars, and photography via telephoto lenses, especially when coupled with lip reading, are all components of effective optical attacks. Television is a threat when the opposition has had a chance to gain considerable access to the target space or occupies an adjoining space. However, a television attack will probably never be encountered because it is not generally cost effective. Light attack devices, including infrared, light-emitting diodes (LED's) and lasers, are somewhat exotic and are also unlikely to be encountered by those working on the non-Federal level. Microphone and wire are probably the oldest of the technical attack strategies. The availability of the devices, their low cost, and the relative lack of technical expertise required by the user makes it highly likely that audio countermeasures will reveal such an attack. Both free space transmitters and carrier current transmitters are described and countermeasures employed against each are outlined. The two different telephone surveillance devices, the telephone tap (an interception of telephone communications) and the compromise (which transforms the telephone into a listening device) are reviewed. An effective audio security program should complicate, or prevent, or detect a technical attack. Generally, the areas to be protected include permanent facilities, such as offices used by political figures on a daily basis, police department facilities, residences, and conference rooms and facilities used temporarily or infrequently, such as hotel rooms and conference facilities. Because each type of facility presents a different challenge, specific countermeasures for each are detailed. Appended material include diagrams; instructions on the use of the search receiver; a list of manufacturers of audio countermeasures search receivers; and an outline of legal restrictions on interception of communications for Federal, State, and local law enforcement officers and for private individuals.