Overview of the Russian market of devices that detect wiretapping of telephone conversations.
Overview of the Russian market of devices that
detect wiretapping of telephone conversations.
The relevance of protecting telephone conversations has set the users of special equipment the task of recognizing and searching for devices that collect information for their subsequent neutralization. Currently, the Russian market of special equipment products is represented by a wide range of devices that allow, with varying degrees of reliability, to detect the presence of listening devices installed on a telephone line. In this review, we will try to assess the effectiveness of using detection devices, classify them according to the principles of searching for listening devices, provide comparative characteristics, and point out their advantages and disadvantages. According to the principle of operation, devices for detecting listening devices can be divided into the following groups:
- Devices for monitoring line voltage.
- Devices for monitoring the surrounding radio environment.
- Devices for monitoring signals on a telephone line.
- Telephone line heterogeneity analysis devices.
- Line asymmetry analysis devices.
- Line parameter nonlinearity analysis devices.
Line voltage monitoring devicesform the largest group of detection devices presented on the market of special equipment. The devices of this group register changes in line voltage using comparators or voltmeters. In this case, if the voltage on the line changes by a sufficient amount, a conclusion is made about a galvanic connection to the line. The main disadvantage of all devices of this group is that they must be installed on a «clean» line, i.e. only new galvanic connections to the line are detected. For example, all devices of this group successfully detect «picking up» the receiver of a parallel telephone during negotiations on the line or connecting «new» telephone bugs with power from the line to the line (series with a resistance of more than 0.5 kOhm, parallel with a resistance of less than 10 kOhm). When measuring line voltage using voltmeters or comparators, it is necessary to take into account «natural» fluctuations in line voltage within up to 1 V, the dependence of line parameters on temperature, humidity, the state of the PBX equipment, the resistance of the adapter pads and other factors. The special equipment market widely offers inexpensive line voltage analyzers based on comparators: AL-2, ATL-2, ATL-3, AT-21, SKAT-3, SKAT-4, etc. Line voltage analyzers are often built in as components of more complex telephone line communication protection devices (for example, interference generators). Such devices include: ATOLL, AT-23, BARRIER-3, KZOT-06, PROKRUST, PROTON, SI-2020, UZT-01, etc. In any case, the sensitivity of line voltage monitoring devices is low and is limited by the instability of telephone line parameters. Replacing a telephone set requires reconfiguring the device, and when connecting for the first time, it is necessary to check the line for «cleanliness» using other technical means.
Radio Environment Monitoring Devicesallow searching for active radio microphones (radio bugs) indoors, inspecting telephone lines, power grids and other communication lines to detect working bugs with a radio channel, spurious emissions, radio exposure and much more. This type of devices includes scanning receivers, field indicators, special frequency meters and spectrum analyzers, spectral correlators, radio monitoring systems, etc. The main advantage of this group of devices is the reliability of the information received about the presence of listening devices with a radio channel, the ability to find a radio transmitting device. The disadvantages of this method include the short detection range of «bugs», mandatory activation of listening devices when searching for them, significant time for monitoring the air, which complicates the operational monitoring of the telephone line. It should be noted that in this group of devices, the most preferable and effective are complex radio monitoring systems (such as OSCOR-5000, KRONA).
The principle of operation of devices for monitoring signals on a telephone lineis based on frequency analysis of signals present on a wire line (electrical network, telephone line, cable signaling lines, etc.). As a rule, devices of this group operate in the frequency range of 40 Hz — 10 MHz, have high sensitivity (at the level of 20 μV), distinguish modulation of the received signal, have the ability to control the received information. With the help of these devices, it is easy to establish the fact of information transmission over the communication line, «HF imposition», etc. Such devices include SCANNER-3, SELSP-31/C, TCM-03, PSCh-4, RTO-30, etc. The main disadvantage of devices of this group as applied to a telephone line is the detection of a narrow class of listening devices. Monitoring of signals on a telephone line is often performed by more complex multifunctional devices (for example, OSCOR-5000, CPM-700, etc.).
Telephone Line Inhomogeneity Analysis Devicesdetermine concentrated resistive or reactive conductivities connected to the line. This is done by measuring the parameters of the signal (most often power) reflected from the line heterogeneity. Periodically appearing on the market prototypes of devices implementing this principle (for example, BOR-1) allow you to determine the distance to the heterogeneity. This is undoubtedly an advantage of this method. However, the short detection range (actually up to 500 m), low reliability (most often contact connections in the line are taken for heterogeneity) of the obtained measurement results make devices of this group effective only for registering «new» connections to the line at small measured distances. The high price and complexity of implementing this detection method, limited functional and technical capabilities of prototypes of devices prevent their distribution on the market.
The most common of Line Asymmetry Analysis Devicesis TPU-5. The operating principle of the device is based on determining the difference in line wire resistance for alternating current and determining the leakage for direct current between the line wires. Measurements are taken relative to the neutral wire of the power grid. The device does not require a «clean» line during operation. Its sensitivity is quite high for detecting almost any bugs contact-connected to the line. The device detects series-connected listening devices with an internal resistance of more than 100 Ohm, parallel with a consumption current of more than 0.5 mA. The device also has a number of disadvantages. With an initial asymmetry of the line (for example, due to long and branched wiring inside the building, the presence of twists, taps, contact connections, etc.), devices of this group erroneously indicate the presence of a series-connected listening device. Changes in line parameters due to changes in climatic conditions, imperfections of the telephone line, leaks due to outdated PBX equipment, etc. lead to an erroneous «definition» of a parallel-connected listening device. And finally, using the neutral bus of the power grid as a “third” wire in the event of a malfunction in the device can lead to the failure of the PBX equipment, telephone line.
In the last few years, devices for analyzing the nonlinearity of line parameters have appeared on the domestic market of special equipmentThus, it can be said that today, despite the development of the market of special equipment for checking telephone lines, there is no universal equipment that allows you to determine the connection to the telephone line. Moreover, inductive and capacitive pickups without a radio channel are not detected by any device from the listed groups. It should be taken into account that the most widespread (up to 95%) are contact-connected devices for listening to conversations with a radio channel and power from the line and devices of the «telephone ear» type. Wiretapping using parallel TA, AON and answering machines is widespread. Much more organizationally complex, expensive and less probable should be considered contactless connection to the line of devices without a radio channel, contact connection of devices with high input resistance and external power without a radio channel, the use of «HF imposition» equipment. As for the choice of all the above devices for checking a telephone line, in each specific case the user must proceed from what types of devices are most likely to be connected to the line. It is necessary to take into account the place where they can be installed and the approximate duration of their work. In our opinion, the most effective at present are radio monitoring devices and devices that analyze the nonlinearity of the line. This is due to the fact that the majority of listening devices operate with power from the telephone line (i.e. contain a nonlinear impedance) and transmit information over the air using a radio channel. Moreover, for operational testing, it is better to use devices that analyze the nonlinearity of the line impedance. When evaluating devices, it is necessary to take into account their additional functions. From this point of view, the most preferable are devices that provide both search functions and functions for protecting telephone conversations. In this sense, the most advantageous according to the «search-protection» criterion is the KTL-400 telephone line controller, which has powerful protective functions. The device allows you to effectively suppress almost any listening devices, including inductive and capacitive pickups, parallel phones, «telephone ear», HF imposition, etc. along the entire length of the telephone line. The device is certified by the STATE TECHNICAL COMMISSION OF RUSSIA. Certificate No. 180.
The prospects for the development of search devices, as it seems to us, lie in the use of new, more effective methods of detecting listening devices, the use of multifunctional devices, as well as the construction of search and protection systems using personal computers.