Technical means of detecting signals of eavesdropping devices.
SILANTYEV Vladimir Anatolyevich
TECHNICAL MEANS OF DETECTING SIGNALS OF EAVESPOOKING DEVICES.
Radio surveillance systems designed to detect eavesdropping devices and other means of unauthorized transmission of information from controlled premises occupy an important place in the arsenal of electronic security specialists.
To solve specific operational tasks, security services use a variety of devices — from pocket indicators to stationary radio monitoring systems for entire buildings. This review highlights the main groups of products for this purpose, with the classification criteria being the principles of their construction and technical capabilities.
ELECTROMAGNETIC RADIATION INDICATORS
The simplest electromagnetic field indicator consists of an antenna, a broadband amplifier, an amplitude detector, and a threshold device that is triggered if the signal at the detector output exceeds an adjustable threshold level. The threshold is set so that the indicator does not react to external radiation (background). As a result, the eavesdropping device is detected only in those points of the room where its field level exceeds the background by 15 — 20 dB.
To increase sensitivity, rejection filters are used, tuned to the frequencies of powerful external sources of a given region (TV and radio broadcasting stations), or spatial compensation of external electromagnetic fields. The latter method is implemented in the dual-antenna Delta V ECM indicator from Audiotel Ltd. (UK), which attenuates external station signals by 20 dB in the frequency range from 20 MHz to 4.2 GHz.
Some devices are equipped with the simplest means of identification: the audio output allows you to listen to the demodulated signal and identify radio microphones using the so-called “acoustic feedback” method, which causes self-excitation in the radio microphone — indicator tract (D006, IP-4, SENTRY).
Signal level meters are useful for localizing radiation sources in space. In particular, the R20 Interceptor detectors from Optoelectronics (USA), D006 and D008 from SmershTechnics are available. Field indicators are small in size and weight (the RMIO indicator from RadioService fits in a wallet), simple, fast, and inexpensive. However, due to insufficient sensitivity and selectivity, they do not provide the required detection reliability. Therefore, these devices are recommended only for preliminary examination of a room or manual localization of radio microphones detected by more advanced systems.
FREQUENCY METERS INDICATORS.
They differ from electromagnetic radiation indicators by a built-in counter — a frequency meter, which measures the frequency of a radio signal that has exceeded a set threshold and helps the operator identify the signal of a listening device. The following models of frequency meter indicators are available on the Russian market: “IPF-4” by Novo, “RICH-2” by Elvira; CUB and SCOUT frequency meters, and the XPLORER search receiver-frequency meter by Optoelectronics. Optoelectronics models provide level indication and frequency memorization for up to 400 external stations to reduce the likelihood of false alarms.
In addition, SCOUT and XPLORER can be connected to a computer and a scanning radio receiver. In this configuration, the indicator is tasked with a preliminary analysis of the electromagnetic environment, followed by verification of the results by the scanner. It should be noted that frequency meter indicators retain the main drawback of field indicators: they can reliably detect a radiation source only in close proximity to it.
NONLINEAR LOCATORS.
They are used for physical detection and location of hidden electronic devices that may be switched off. A nonlinear locator emits a microwave signal and receives its second harmonic, which is formed due to nonlinear effects in semiconductor devices. In order to eliminate re-radiation created by metal-oxide contacts in building structures, more advanced products receive and analyze the levels of not only the second, but also the third harmonic. Russian and foreign companies produce nonlinear locators with pulsed (with a power of up to several kW per pulse) and continuous radiation.
The former have a greater detection range, but the increased output power can adversely affect the operator.
SPECTRUM ANALYZERS.
A spectrum analyzer is a measuring device that is widely used in radio reconnaissance to detect and identify signals by the operator based on the shape of their spectra. With high sensitivity, it can be connected to an antenna or cable lines and display spectral panoramas or spectra of individual radio signals on the screen. The main advantage of spectrum analyzers is their high scanning speed and clear display of results. However, they usually do not have the means to automate detection operations and are quite expensive, especially in the range above 100 MHz. An acceptable compromise is the combination of a low-frequency spectrum analyzer and a scanner.
AOR Ltd. produces the SDU-5000 analyzer, designed to display spectra at the output of the IF amplifier of scanning radio receivers.
SCANNING RADIO RECEIVERS.
A scanning radio receiver is an integral part of any professional radio intelligence system. Modern scanners can automatically reconfigure in a range of up to several GHz and detect signals with different types of modulation. These products can be divided into two groups. The first owe their origin to measuring and military equipment. Such receivers have unique parameters, but their size, weight and, most importantly, cost are very high.
The products of the second group appeared as a result of the evolution of communication, mainly short-wave, radio receivers. Achievements in microelectronics made it possible to create inexpensive models that are quite suitable for detecting signals from eavesdropping devices. The most popular now are pocket and desktop scanners from Japanese companies AOR Ltd. (AR3000A, 8000, 5000) and Icom Inc. (IC-R10, R8500). Scanners with high sensitivity, frequency selectivity and a wide range of analysis detect radio microphone signals with high reliability. However, their use as autonomous devices requires a very high qualification of the operator due to the limited capabilities for input, storage and display of data.
COMPUTER PROGRAMS FOR CONTROLLING SCANNERS.
Most modern scanners can be connected to a computer, which significantly expands the capabilities of control, display and storage of information about the signals being studied. Currently, a significant number of different scanner control programs are known, many of which are distributed via the Internet. Along with the functions of control, as well as accumulation and processing of data on radio spectra, specialized software is capable of solving individual problems of identifying signals from listening devices.
In particular, such capabilities are provided in the SEDIF PLUS, SEDIF PRO, SEDIF SCOUT, FILIN programs from Nelk. They compare the recorded spectra with typical ones stored in libraries, analyze spectrum changes during acoustic impact on radio microphones, compare spectral panoramas for different moments in time or for two spatially separated antennas.
MICROCOMPUTER COMPLEXES FOR DETECTING RADIO MICROPHONES.
These products combine signal search equipment: antennas, adapters for connecting to cable lines, specialized scanning radio receivers, as well as data display and recording devices. Control and display functions are assigned to a microcomputer, which also organizes individual automatic procedures for detecting and identifying signals.
For example, the Scanlock ECM+ system from Audiotel Ltd., operating in the range from 10 MHz to 4 GHz (when analyzing cable lines — from 8 kHz to 10 MHz), searches for the maximum signal level in the fast scanning mode or conducts radio surveillance, retuning the receiver in increments from 1 to 100 kHz in a given range. Signal identification is provided by the “acoustic feedback” method.
A similar portable complex OSC-5000 (OSCOR) from Research Electronics Inc. (USA) is placed in an attaché case and analyzes wire lines and power supply networks at frequencies from 50 Hz to 15 kHz, radio signals in the range from 10 kHz to 3 GHz and optical IR radiation with a wavelength from 850 to 1070 nm. Signal identification is performed automatically by the “acoustic feedback” method or by the degree of correlation of the demodulated signal and the natural acoustic background of the room. Acoustic probing from three positions is used for localization. The complex can be equipped with demodulators and a display for receiving television signals of all standards.
COMPUTER COMPLEXES FOR CONTROL OF PREMISES AND BUILDINGS.
As an alternative to expensive foreign-made microcomputer systems, Russian developers offer hardware and software systems based on standard computer units and an inexpensive scanner, which are equipped with additional hardware and programs. The advantages of this approach are obvious: a modern personal computer is inexpensive and has the ability to implement “intelligent” detection procedures of any complexity.
In particular, the RS1000 desktop and portable systems from Radioservice, which are manufactured to work with the AR3000A, AR8000 and AR5000 scanners, detect signals from eavesdropping devices with any type of modulation and coding, indicate the location of radio microphones with an accuracy of several centimeters and, if necessary, block their operation. The system is equipped with equipment for analyzing signals in the power supply network, wired and optical channels.
The NPC Nelk offers automated systems for detecting and localizing information leakage channels, KRONA-4, KRONA-5N and KRONA-6N. The Irkos company offers a wide range of multifunctional systems. Among them are ARK-PK-P, ARK-D1, ARK-DZ, ARK-MK and others. Novo OJSC entered the market with its own development — multifunctional radio control complex “KRK”.
In conclusion of the review, we can conclude that currently there is a wide range of devices on the market of electronic security systems, with the help of which specialists can detect with a high degree of reliability means of unauthorized transmission of information from controlled premises. The choice of these devices depends on the level of training of specialists and on the funds allocated by the management for measures to ensure the security of their organization.
Source: Special Equipment magazine.