Introduction

Eavesdropping is the unauthorized real-time interception of a private communication, such as a phone call, instant message, video-conference or fax transmission .

The term eavesdrop derives from the practice of actually standing under the eaves of a house, listening to conversations inside.

Pickup Device :  

  A microphone, video camera or other device picks up sound or video images and converts them to electrical impulses. Some listening devices can store information digitally and transmit it to a listening post at a predetermined time.

A Bug:

  A "Bug" is a device which is placed in an area which had to intercepts communications and transmit them out of that area to a listening post.

There are four categories of "bugs" Acoustic, Ultrasonic, RF and Optical.

• Acoustic:

Acoustic is the placing of a water glass stethoscope, or rubber tube into an area and directly intercepting the communication with the naked ear.

Simpler way to eavesdrop.

• Ultrasonic:

Ultrasonic is a technique to convert the sound into an audio signal above the range of human hearing. The ultrasonic sound is then intercepted nearby and converted back to audio.

• Radio Frequency:

Radio Frequency "(free space)" is the most well known type of bugging method. A radio transmitter is placed in an area or in a device. Extremely easy to detect, but cheap, disposable and difficult to trace back to the person who planted it (including mains borne devices "closed loop").

A type of Radio Transmitter.

• Optical:

Optical is a bugging method that converts sound (or data) into an optical pulse of light. Than it is reflected from a reflecting surface and received at a receiver which might contain electronics circuitry for processing of the pulse of light back in sound.

Eavesdropping using laser beam.