Efficiency of using an active speech information protection device based on special signal generators.

Efficiency of using an active speech information protection device based on special signal generators.

Possible channels for speech information leakage.

Depending on the physical nature of the origin of information signals, the environment for the propagation of acoustic vibrations and the methods of interception, mechanical channels for the leakage of acoustic (speech) information can be divided into air, vibration, optical-electronic and parametric.

Air technical channels for information leakage.

In these channels, the acoustic signals are transmitted through air, and miniature, highly sensitive microphones and special directional microphones are used to intercept them.

Miniature microphones are combined (or linked) with portable sound recording devices or miniature transmitters.

Autonomous devices that structurally combine miniature microphones and transmitters are called acoustic bugs.

Voice information intercepted by eavesdropping devices can be transmitted via a radio channel, an optical channel, an alternating current network, VTSS connecting lines, external conductors (water supply and sewer pipes, metal structures, etc.).

Moreover, not only electromagnetic but also mechanical ultrasonic vibrations can be used to transmit information via pipes and metal structures.

Reception of information transmitted by eavesdropping devices is carried out, as a rule, on special receiving devices operating in the corresponding wave range. However, there are eavesdropping devices, the reception of information from which can be carried out from an ordinary telephone set.

Such devices are installed either directly in the body of a telephone set located in a controlled room and called a “monitor telephone”, or are connected to a telephone line, most often to a telephone socket.

A secondary device structurally combines a miniature microphone and a special communication unit, and is often called a “telephone ear”.

The use of acoustic information bookmarks requires penetration into the controlled object (into the premises).

In the event that this fails, directional microphones are used to intercept speech information.

Vibration technical channels.

In vibration technical channels of information leakage, the propagation medium of acoustic signals are the structures of buildings, structures, sewers and other solid bodies. In this case, contact microphones (stethoscopes) are used to intercept acoustic vibrations.

It is also possible to intercept information via a vibration channel using bugs. Basically, a radio channel is used to transmit information, so such devices are often called radio systems.

It is possible to use bugs to transmit information via an optical channel, as well as via an ultrasonic channel (via the metal structures of a building).

Electroacoustic channels for information leakage.

Electroacoustic information leakage channels arise due to electroacoustic transformations of acoustic signals into electrical ones, and include the interception of acoustic oscillations through VTSS, which have a “microphone effect”, as well as by high-frequency imposition.

Some elements of the VTSS, including transformers, inductance coils, electromagnets of secondary electric clocks, telephone bells, fluorescent lamp chokes, etc. have the ability to change their parameters (capacitance, inductance, resistance) under the influence of an acoustic field created by a source of acoustic vibrations.

Changes in parameters lead either to the appearance of an EMF on these elements, changing according to the law of the acting information signal (acoustic field), or to the modulation of currents flowing through these elements by the information signal.

In addition to the specified elements, the VTSS may contain directly electroacoustic transducers: some fire alarm sensors, loudspeakers of the retransmission network, etc.

Moreover, of the VTSSs that have a “microphone effect”, subscriber loudspeakers have the greatest sensitivity to the acoustic field.

Interception of acoustic vibrations in this leakage channel is carried out by directly connecting special highly sensitive low-frequency amplifiers to the VTSS connecting lines.

For example, by connecting such devices to the connecting lines of telephone sets with electromechanical ringing bells, it is possible to listen in on conversations taking place in the rooms where these sets are installed.

A technical channel for information leakage by means of high-frequency imposition can be implemented by means of unauthorized contact introduction of high-frequency currents into lines that have functional connections with nonlinear or parametric elements of the high-frequency telephone system, on which the high-frequency signal is modulated by the information signal.

The information signal in these elements of the high-frequency telephone system appears as a result of the “microphone effect” of the latter.

Due to the fact that nonlinear or parametric elements for the HF signal, as a rule, represent an unmatched load, the modulated HF signal will be reflected from it and propagate in the opposite direction along the line or radiated.

Special receivers with high sensitivity are used to receive reflected or radiated HF signals. Pulse signals can be used to eliminate the influence of the probing and re-reflected signals.

Optical-electronic technical leakage channel.

This channel is formed by irradiating thin reflective surfaces (glass, paintings, mirrors) vibrating in an acoustic field with a laser beam.

The reflected laser radiation is modulated in amplitude and phase (according to the law of surface vibration) and is received by a laser radiation receiver, during demodulation of which speech information is extracted.

Moreover, the laser and receiver can be installed in the same or different places.

Based on the above-mentioned features of the TSPI and VTSS, as well as the capabilities of modern technical intelligence, it can be concluded that there is a potential danger of the emergence of a technical channel for information leakage.

And this problem should be solved by improving the equipment used (TSPI and VTSS), as well as the use of active protection means, which the designed device will serve.

Possibilities of technical intelligence and equipment for collecting information.

Radio microphones

Acoustic radio eavesdropping systems (radio bugs) provide one of the methods of unauthorized access to sources of confidential information — eavesdropping — with the transmission of perceived conversations or sound signals of equipment to the intruder via a radio channel.

The practice of using such systems to obtain intelligence information has shown that, according to their application and design features, they are divided into microphone and telephone radio bugs.

To effectively combat radio bugs, it is necessary to have an idea of ​​the features of their construction and main characteristics. Therefore, first, let's consider the general principles of operation and construction of radio bugs.

Microphone radio bugs are miniature radio transmitters with a built-in or external microphone, which are used if the radio transmitter for some reason cannot transmit information from the area of ​​interest, for example, due to the peculiarities of radio wave propagation or a strict radio control regime.

The simplest radio bugs contain three main units that determine the technical capabilities and methods of their use:

• • a microphone that perceives acoustic vibrations of talking persons and converts them into electrical signals;
  • a radio transmitter that receives electrical signals from a microphone and transmits them via a radio link to a receiver, allowing an attacker to perceive the content of the conversations;

• • radio transmitter power source, determining the duration of continuous operation of radio bugs.

Radio microphones are the most common technical means of reconnaissance.

Their popularity is explained, first of all, by the convenience of their operational use, low cost, very small size.

The microphone determines the zone of acoustic sensitivity (up to 20-30 meters), the radio transmitter — the range of the radio line.

The determining parameters in terms of range for a transmitter are power, carrier frequency stability, frequency range, and modulation type.

Technical data for radio microphones are within the following range:

Weight from 5 to 350 g.
Dimensions from 1 cm3 to 8 dm3
Frequency range from 27 to 900 MHz
Range without a repeater from 10 to 1500 m
Continuous operation time. from several hours to several years.

Table 1.1.

Technical data for industrial radio microphones.