Are you being bugged?

Are you being tapped?.

Are you being tapped?

The relevance of protecting telephone conversations from wiretapping has set the users of special equipment the task of recognizing and finding devices for collecting information for their subsequent neutralization. Currently, the Russian market of special equipment offers a wide range of devices that allow, with varying degrees of reliability, to detect the presence of listening devices 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 conditionally 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;

• devices for analyzing telephone line heterogeneity;

• devices for analyzing line asymmetry;

• devices for analyzing the nonlinearity of line parameters.

Devices for monitoring line voltageform the largest group of detection devices presented on the market of special equipment. They register changes in voltage in the line using comparators or voltmeters. If the voltage changes by a certain value, a conclusion is made about a galvanic connection to the line. The main disadvantage of all devices in this group is the need to install them on a «clean» line, since they only detect new galvanic connections. For example, all devices in this group successfully detect the fact of picking up the handset of a parallel telephone set during negotiations on the line or connecting new telephone bugs to it that are powered by the line (serial — with a resistance of more than 0.5 kOhm, parallel — with a resistance of less than 10 kOhm). When measuring voltage in the line using voltmeters or comparators, its natural fluctuations within up to 1 V, the dependence of the line parameters on temperature, humidity, the state of the PBX equipment, the resistance of the adapter pads and other factors should be taken into account.

The special equipment market is widely represented by inexpensive line voltage analyzers based on comparators: AL-2, ATL-2, ATL-Z, AT-21, «SKAT-3», «SKAT-4», etc.

Line voltage analyzers are often built into more complex devices for protecting telephone conversations (for example, interference generators). Such devices include «ATOLL», AT-23, «BARRIER-3″, KZOT-06, DPROKRUST», «PROTON», UZT-01, etc. In any case, the sensitivity of devices in this group is low and is limited by the instability of the telephone line parameters. Replacing a telephone requires reconfiguring the device, and when connecting for the first time, it is necessary to check the line for «cleanliness» using other technical means.

Devices for monitoring the surrounding radio environmentallow you to search for active radio microphones indoors, examine the telephone line, power grid and other communication lines to identify working bugs with a radio channel, side emissions, radio exposure and much more. This type of device includes scanning receivers, field indicators, special frequency meters and spectrum analyzers, spectral correlators, radio monitoring systems.

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 and the ability to find them. The disadvantages include the short range of detection of radio transmitting devices, the mandatory activation of listening devices when searching for them, a significant time of monitoring the air, which complicates the operational monitoring of the telephone line itself. 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). 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 the modulation of the received signal, have the ability to acoustically monitor the received information. With their help, it is easy to establish, for example, the fact of information transmission over the communication line or high-frequency interference. Such devices include SCANNER-3, SELSP-31/C, TSM-OZ, PSCh-4, RTO-ZO, «OBLAKO». The main disadvantage of devices of this group as applied to telephone line protection is the detection of a narrow class of listening devices. Signal monitoring on a telephone line is often performed by more complex multifunctional devices (for example, OSCOR-5000, SRM-700, ST031 «PIRANHA»).

Devices for analyzing telephone line heterogeneitydetermine the concentrated resistive or reactive conductivities connected to the line 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, which is an undoubted advantage of this method. However, the short detection range (in reality — up to 500 m) and the low reliability of the obtained measurement results (most often contact connections in the line are taken for heterogeneity) 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 prevent their distribution on the market.

The most common device for analyzing line asymmetryis TPU-5. The device operates by determining the difference in line wire resistance for alternating current and determining the leakage for direct current between line wires. Measurements are taken relative to the neutral wire of the power grid. Unlike many of the devices we have already reviewed, the device does not require a “clean” line during operation. Its sensitivity is quite high for detecting virtually any bugs connected to the line: connected in series with an internal resistance of more than 100 0 m and parallel with a consumption current of more than 0.5 mA.

The device is not without some disadvantages. With the 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 serially connected listening device. Changes in line parameters due to changes in climatic conditions, defects in the telephone line, leaks due to outdated PBX equipment lead to an erroneous determination 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 failure of the PBX equipment and the telephone line.

In the last few years, devices for analyzing the nonlinearity of line parameters have appeared on the domestic market of special equipment, the operating principle of which is based on the analysis of the nonlinearity of the impedance of the telephone line. This group, in turn, is divided into two categories: devices that determine the nonlinearity of a two-wire de-energized line, and devices that operate on a real telephone line. The first (AT-2, «VIZIR», LBD-50, etc.) have high sensitivity and allow you to determine almost any nonlinear data collection devices connected to the line.

The detection principle is based on measuring the harmonics of the 220 V ~ 50 Hz test signal supplied to the section of the line under test. When the section length increases to several tens of meters, the sensitivity of detecting nonlinear devices drops sharply. A significant disadvantage of the devices in this subgroup is the short detection range, limited by physical accessibility to the line wires and the need to disconnect the telephone line from the PBX during testing. These operating features do not allow for operational monitoring of the telephone line and limit the testing range. The devices are most suitable for periodic testing of de-energized short sections of lines (telephone, power grid, alarm) inside a building.

Of the above-listed devices, the LBD-50 has the widest functionality: in addition to its main task, it allows the operator to determine the insulation resistance of the line, detect high-resistance capacitive connections, etc.

Devices operating on a real telephone line (KTL-Z, SELSP-18/T, KTL-400) have lower sensitivity compared to devices of the previous subgroup. This is due to the fact that interference, special signals of the automatic telephone exchange, and industrial frequency pickup present on the line do not allow to actually achieve similar indicators. However, their sensitivity is quite sufficient to detect almost all known listening devices powered by the telephone line and having a nonlinear impedance. On the other hand, the ability to operate on a real telephone line, the speed of testing (no more than 5 minutes) without disrupting the normal operation of the line, the maximum possible range of detecting listening devices (from the telephone set to the automatic telephone exchange), the optional «clean» line at the time of connecting the device, the absence of dependence of the line test results on reactive inhomogeneities, poor-quality contacts (twists), current leaks make devices of the second subgroup the most attractive in operation.

Their undoubted advantages include multifunctionality. The SELSP-18/T analyzer is designed as a search device with an autonomous power supply and, as additional functions, detects HF interference equipment and the presence of audio signals on the line. The KTL-Z and KTL-400 controllers, in addition to the search function, perform the function of protecting conversations on the line from information leakage. For example, the KTL-400 is fully automated and has a digital noise generator with an automatically tunable spectrum. The device effectively counteracts parallel telephone sets, telephone bugs powered from the line or externally, dictaphones connected to the line via contact or inductive pickups, microphones and radio microphones powered from the line. The device also protects telephones from HF interference equipment, detects and disables “telephone ear” type equipment. The KTL-400 implements a new protection method — compensation for constant line voltage during a conversation, which allows you to completely disable parallel listening devices powered from the line. The device can be used both on city and local lines (with mini-ATS). And finally, the device can be used to check any two-wire de-energized lines (electricity grid, alarm, etc.).

Despite the large number of different types of devices for checking and monitoring telephone lines, today there is no universal equipment that allows with 100% probability to guarantee the detection of any listening devices. And such devices as inductive 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. Listening using parallel telephone sets, AONs and answering machines is quite common.

Significantly more complex organizationally, expensive and therefore 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 supply without a radio channel, the use of HF-imposition equipment.

To select the most effective of the above devices, the user must proceed from assumptions about the most probable types of devices that can be connected to a specific line.

Further actions should be taken taking into account the possible locations of their installation and the estimated duration of operation. In our opinion, the most effective at present are radio monitoring devices and line nonlinearity analyzers.

This opinion is based on the fact that the majority of listening devices operate with power from the telephone line (i.e. contain nonlinear impedance) and transmit information over the air using a radio channel.

For operational testing, it is better to use devices that analyze the nonlinearity of the line impedance. When choosing, it is necessary to take into account the availability of additional functions. The most preferable are devices that provide both search functions and telephone conversation protection functions, and here the most advantageous according to the «search-protection» criterion is the KTL-400 telephone line controller, which has powerful protective functions.

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, and the construction of search and protection systems using personal computers.