RU2145153C1 - Method for protection against unauthorized eavesdropping in intervals between telephone talks and device which implements said method - Google Patents

Abstract

FIELD: security equipment, in particular, protection against eavesdropping equipment using telephone line for transmission of information or as power supply or as information source about line condition for making decision about eavesdropping. SUBSTANCE: method involves automatic alteration of electric parameters at user's end of telephone line under protection. Said line passes through room to be protected and ends with standard telephone set. Remote actuating unit, which is inserted into telephone line outside of room under protection, provides disconnection of user's end of input telephone line for period when telephone line is not used for telephone talks. Device also provides connection in automatic mode according to commands which enter actuating unit from control unit, which is located directly in front of telephone set, so that connection is restored while call signals from exchange system are received or during talk. When telephone talk or call signals are finished, device disconnects user's terminal end of telephone line under protection from telephone line. EFFECT: increased functional capabilities. 3 cl, 5 dwg

Description

 The present invention relates to devices for protection against unauthorized listening to conversations in the premises and relates, in particular, to devices for protection against eavesdropping using devices (bookmarks) using a telephone line as a line for transmitting intercepted information, or as a power source, or as a source of information about the state of the decision line on enabling the listening mode of the room.

 Examples of such listening devices are given in the book of A. Lysov. and A. N. Ostanenko, “Telephone and Security (Problems of Information Security in Telephone Networks),” “PPSh Laboratory,” St. Petersburg, 1995, pp. 20, 23-26. One of the options for obtaining information is associated with the phenomenon of the so-called high-frequency (HF) imposition. At the same time, with respect to the general case (which is better to use the earth, heating pipes, etc.), RF oscillations with a frequency of 150 kHz and higher are fed to one drive. Through the circuit elements of the telephone, even if the handset is not picked up, the high-frequency oscillations arrive at the microphone, where they are modulated by speech. Information is received relative to the common housing through the second wire of the line.

 To improve the quality of the intercepted information, it is desirable to connect as close to the telephone as possible, which significantly reduces the efficiency of the system.

 Combined systems of the LST-4 type occupy a significant place on the market, which make it possible to intercept both telephone calls with the handset off and indoor calls with the handset lying on the device. Power is supplied from the telephone line while consuming a small amount of current, therefore the transmission range is small, as it is undesirable to increase the current consumption from the telephone line (no more than 2 mA).

 A separate place is occupied by systems that are not intended for intercepting telephone conversations, but for acoustic monitoring of rooms where telephone sets are located or telephone line wires are laid. So, for example, a “telephone ear” is connected in parallel to a telephone line (wall socket) in the desired room. In principle, a telephone is not required. To listen to the premises, you must call the phone number on the line of which the device is installed. Having heard 1-2 standard beeps of the PBX “the subscriber does not answer” (after which the tone of the beeps changes), you need to say a few words (give any sound signal). After that, the device will begin to transmit acoustic information from the premises via a telephone line with fairly good quality. On the plus side, the device is powered by a telephone line. The disadvantage of the "telephone ear" is the complete dependence on the behavior of the subscriber of the telephone number to which the connection is made.

 In addition, it is possible to use a telephone line to transmit information from a microphone installed in the room. In this case, a carrier frequency in the range from tens to hundreds of kHz is used in order not to interfere with the normal operation of telephone communications. One of the options for implementing such a system is the ST-01 signal receiver. The P10 sensor is installed in a telephone wall jack. For transmission, a frequency of 100 ± 10 kHz is used. Modulation is frequency. To register information, a tape recorder or voice recorder is connected to the receiver, the range of information transfer in the system is up to 200 m. However, in real conditions, the range of such systems depends on a number of factors: the quality of the telephone line, the laying of telephone wires, the presence of a broadcast network in a given area, and the availability of a computer or other equipment, etc.

 Known devices for protecting against unauthorized eavesdropping in rooms using the above bookmarks, namely: soundproof booths, devices for generating high-voltage pulses, burning bookmarks, devices for detecting (location) acoustic bookmarks, as well as devices that do not pass high-frequency voltage to the telephone set.

 These devices either make the conversation inaudible for the bookmark microphone, either confirm the bookmark, or allow it to be detected and neutralized, or, reducing the level of high-frequency voltage, do not allow the use of elements of the telephone as a microphone.

 In the first case, the installation of a soundproofing cabin requires significant material costs, a large free area in the room and a relatively long time for installation, although together with other methods it allows to obtain a strategic degree of information protection.

 The second option, because it uses high-voltage pulses, is not always applicable and can lead to damage to the serving PBX, especially if the office version of the PBX is used, as well as to electrical breakdown of the line insulation. In addition, it is necessary to repeat this procedure periodically to destroy newly installed listening devices.

 The third option using devices for detecting acoustic bookmarks requires a significant investment of time for detecting the transmission channel (frequency, in the case of a radio transmitter), as well as certain skills in finding these bookmarks and does not allow to detect acoustic bookmarks that are triggered by certain commands (telephone ear) or under certain conditions, for example, in time, and, in addition, as in the second embodiment, it is necessary to repeat this procedure periodically to detect a newly installed GOVERNMENTAL listening devices. The fourth option requires refinement of the telephone.

 The closest in technical essence to the present invention is an electronic device for the integrated protection of the telephone line "Octopus" or "Proton" (see passports of the products "Proton" or "Octopus", "Electronic device for the integrated protection of the telephone line" of OJSC "Radius", Leninsky pr 41/2 tel. 135-33-94, Moscow), which implements the method, the essence of which lies in the fact that in the intervals between negotiations the telephone line is disconnected from the telephone, which is guaranteed to prevent the signal "HF imposition" on telephone th apparatus. To prevent high-frequency voltage (from HF-imposition equipment) getting on the telephone, a telephone line break inside the device itself is used. The line is broken by means of a relay automatically at the moment when the handset of the telephone is placed on the levers. An additional sound calling device is built into the device, which remains connected to the telephone line and notifies the user of incoming calls, as ringing signals also do not reach the telephone set.

 This device during telephone conversations allows you to change the electrical parameters on the end of the telephone line, namely: to change the DC component of the voltage in the telephone line during a conversation in the direction of increase by about 2-3 times. With increasing voltage, the direct current in the line decreases. Most of the technical means of unauthorized receipt of information use the telephone line for their power supply and / or as a source of information for deciding on their transition from standby to working mode due to a power surge when the telephone is off-hook. Therefore, with an increase in the DC component of the voltage on the line, the power regimes of such unauthorized access devices are violated or their false operation or shutdown occurs. So, at a sufficiently low current in the telephone line 10 ... 7 mA, the voltage in the line is 48 ... 53 V, respectively, which leads to the disconnection of devices that respond to picking up the telephone handset, while the "Proton" with the telephone line at low currents does not affect the quality of communication.

 The disadvantage of this method of protection and a device for its implementation is that the device must be located in a room next to the telephone and all standard signals are available on the telephone line stretched across this room, so it is possible to install listening devices in a room using a power line or to transmit intercepted information on it. In addition, the known method and device can counteract only some of the above information interception devices. So, listening devices that do not load the line with direct current (headphones connected to the line through an isolation capacitor, etc.) are detected only when the active noise interference mode is turned on in the audio frequency range, which completely clogs the communication channel.

 The basis of the present invention is the creation of a method of protection against unauthorized listening to conversations in the room between telephone calls and a device for its implementation, which provides a full guarantee of blocking all types of listening devices due to the temporary elimination of the source of danger in the room.

 The problem is solved in that in a method of protection against unauthorized listening to conversations in between telephone conversations using an unauthorized access device using a telephone line to transmit intercepted voice information and / or to power and / or obtain information about the state of the telephone line and receive decisions to enable the mode of interception of voice information, which consists in blocking these devices of unauthorized access by changing the electrical parameters according to the invention, automatic control of the change in electrical parameters on the final protected section of the telephone line is carried out, namely, that the final protected section of the telephone line passing through the protected room and ending with a standard telephone set is disconnected from the rest of the telephone line outside the protected premises anywhere for a time when the telephone line is not used for telephone conversations, and automatically ki reconnect the end of the protected area with the telephone line for the duration of the ringing signals from the automatic telephone exchange or for the duration of telephone conversations with the standard telephone at the initiative of the subscriber or partner calling through the automatic telephone exchange, and then again upon completion of negotiations or completion of the ringing its specified final protected area is automatically disconnected from the telephone line.

 The problem is also solved by the fact that in the device for protection against unauthorized listening to conversations in the room between telephone calls, which contains a blocking unit for unauthorized access devices and for the operation of a standard telephone set, according to the invention, a blocking unit for unauthorized access devices and for a regular telephone set is made in the form of a remote executive unit installed outside the protected premises and containing a com a mutating device connected to an incoming section of the telephone line and a control command extraction circuit connected thereto, the device comprising a control unit connected to a telephone line installed directly in front of a standard telephone set connected to it and containing an electronic activity detector of a standard telephone set and connected control unit to it.

 Due to the complete rupture (de-energization) of the line section in the protected room at a time when the line is not used for telephone conversations with automatic reconnection when ringing signals are received from the telephone exchange or when the handset of the regular telephone is picked up and the line is automatically re-opened after the end of the communication session, or, if the handset has not been picked up, after the end of the ringing signals, a highly effective protection of the telephone line from information leaks is provided, which is a source of danger listening to conversations indoors. Thanks to the present invention, protection is provided not only against previously installed bookmarks, but also makes useless the installation of new acoustic bookmarks of this kind. In addition, the small passage capacity of the open contacts of the switching device makes it impossible to listen to the room using devices using the RF imposition method, since the amplitude of the RF signals penetrating the telephone set is negligibly small and insufficient for the normal operation of these devices, and therefore there is no need to use additional protection devices against RF imposition.

In the future, the invention is illustrated by a specific example of its implementation and drawings, in which:
FIG. 1 shows a diagram of the connection and placement of blocks of a protection device relative to the protected premises;
FIG. 2 is a functional diagram of a protection device;
FIG. 3 - diagrams of the passage of electrical signals in the event of a signal on an incoming section of the telephone line with the subsequent removal of the handset of a standard telephone
FIG. 4 - the same, but in the case of a called signal on an incoming part of the telephone line without subsequent pick-up;
FIG. 5 - the same, but in the case of lifting the handset for negotiations.

 The device for protecting against unauthorized listening to conversations in a room between telephone calls contains a unit for blocking devices of unauthorized access and ensuring the operation of a standard telephone set, made in the form of a remote executive unit 1 (Fig. 1) installed outside the protected room 2 and connected to the incoming section 3 telephone line 4. The device also contains a control unit 5 connected to the telephone line 4 at its final protected area 6 directly per d connected thereto regular telephone 7.

 The remote actuating unit 1 (Fig. 2) contains a rectifier 8, one input 9 of which is connected through an isolation capacitor 10 to the incoming section 3 of the telephone line 4. The output of the rectifier 8 is connected to the winding 11 of the polarized relay of the switching device, and the other input 12 of the rectifier 8 is connected to one group of movable contacts 13 of the polarized relay connected to the incoming section 3 of the telephone line 4, as well as through the protected section 6 to the command allocation circuit of block 5. Mobile contacts 15 of the other group of the polarized relay are connected They are connected to the incoming section 3 and through a diode 16 connected in series to isolate a pulse carrying information about switching on - a positive polarity, diode 17 to separate a pulse carrying information about a reset - negative polarity, and are connected through a final protected section 6 to a control selection circuit 14 teams. In addition, the diodes 16 and 17 through the winding 18 of the polarized relay are connected to the control command allocation circuit 14.

 Block 5 also contains an electronic detector 19 of the activity of a standard telephone set connected to a standard telephone set 7 and a control command extraction circuit 14.

The proposed method of protection against unauthorized listening to conversations in the room in between telephone calls is as follows. In the initial state shown in FIG. 2, the incoming section 3 of the telephone line 4 is disconnected from its final protected section 6 and the device is in standby mode (interval t ₀ -t ₁ in Fig. 3).

Consider the case of a ringing signal coming in from an incoming section 3 of a telephone line 4 followed by picking up the handset of a standard telephone set 7. When a ringing signal is received from a telephone exchange (not shown), the alternating voltage of the ringing package (interval t ₁ -t ₃ , Fig. 3) comes through a junction box a capacitor 10 (Fig. 2) to the input 9 of the rectifier 8. From the output of the rectifier, the converted signal is fed to the winding 11 of the polarized relay of the switching device, as a result of which its contacts 13 and 15 switch to the opposite state one (interval t ₁ -t ₂ in Fig. 3b), while the incoming section 3 (Fig. 1, 2) of the telephone line 4 is connected to its final protected section 6 (time t ₂ , Fig. 3c), and the input 12 ( Fig. 2) of the rectifier 8 is disconnected from the incoming section 3. Ringing signals through the final protected section 6 of the telephone line 4 and the electronic detector 19 are supplied to the standard telephone set 7 (interval t ₂ -t ₃ , Fig. 3c). When the handset of the apparatus 7 is removed, its usual connection with the caller is ensured (interval t ₃ -t ₄ ). At the end of the conversation, when the handset is put on the apparatus 7 (Fig. 3, moment t ₄ ), the electronic detector 19 will transmit a signal about this to the control command allocation circuit 14 (Fig. 3, interval t ₄ -t ₅ ), which will give a reset pulse of negative polarity (Fig. 3, interval t ₅ -t ₆ ). This pulse through the end of the protected section 6 of the telephone line 4 (Fig. 3B, interval t ₅ -t ₆ ) and the diode 17 will go to the coil 18 of the polarized relay (Fig. 3g. Interval t ₅ -t ₆ ), which causes the switching of contacts 13 and 15 to the initial state (Fig. 3, moment t ₆ ). The device will return to its original state - standby mode (Fig. 3, moment t ₆ -t ₇ ).

Consider the operation of the device in the case of ringing signals on the incoming section 3 of the telephone line 4 without subsequent removal of the handset. The initial state is the incoming section 3 is disconnected from the final protected section 6, and the device is in standby mode (Fig. 4, interval t ₀ -t ₁ ). When the call signal from the telephone exchange arrives at the incoming section (Fig. 3, interval t ₁ -t ₃ ), the alternating voltage of the call package through the isolation capacitor 10 (Fig. 2) is supplied to the input 9 of the rectifier 8. From the output of the rectifier 8, the converted signal is fed to the winding 11 of the polarized relay, which causes the switching of contacts 13, 15 to the state opposite to the initial one (Fig. 4b, interval t ₁ -t ₂ ). In this case, the incoming section 3 is connected to the final protected section 6 (Fig. 4c, moment t ₂ ), and the input 12 of the rectifier 8 is disconnected from the incoming section 3 (Fig. 4b, moment t ₂ ), and ringing signals through the protected section 6 and electronic detector 19 is supplied to a standard telephone set 7 (Fig. 4c, interval t ₂ -t ₃ ). If the handset of the apparatus 7 is not picked up before the end of the passage of the series of ringing signals (Fig. 4, moment t ₃ ) after a time slightly longer than the period of the ringing parcels (Fig. 4, interval t ₃ -t ₄ ), the electronic detector 19 will not transmit a signal about removing the tube in the circuit 14 allocation of control commands, which will give a reset pulse of negative polarity (Fig. 3 interval. t ₄ -t ₅ ). The pulse through the final protected section 6 (Fig. 4c, interval t ₄ -t ₅ ) and diode 17 will go to the coil 18 of the polarized relay (Fig. 4d, interval t ₄ -t ₅ ), which causes the relay contacts 13, 15 to switch to the original position (Fig. 4, moment t ₅ ). In this case, the device will return to its original state - standby mode (Fig. 4, interval t ₅ -t ₆ ).

In the case of picking up the handset (Fig. 5, moment t ₁ ), the electronic detector 19 (Fig. 2) will transmit a signal about this to the control command extraction circuit 14, which will give a positive polarity switching pulse (Fig. 5, interval t ₁ -t ₂ ) This pulse through the final protected section 6 (Fig. 5B, interval t ₁ -t ₂ ) and the diode 16 will go to the coil 18 of the polarized relay (Fig. 5d, interval t ₁ -t ₂ ), which will cause the switching of contacts 13, 15 of the relay the opposite position to the original (Fig. 5, moment t ₂ ). At the same time, the incoming section 3 of the telephone line 4 is connected to its final protected section 6, and the input 12 of the rectifier 8 is disconnected from the incoming section 3, thereby providing a direct connection of the standard telephone set 7 to the incoming section 3. The following are standard for a city telephone line steps for establishing a connection with the called party:
t ₂ -t ₃ - the response of the PBX (continuous beep);
t ₃ -t ₄ - dialing by the caller;
t ₄ -t ₅ - waiting for the connection (long beeps);
t ₅ - the time of lifting the handset by the called party;
t ₁ -t ₂ - conversation of two subscribers.

At the end of the conversation, when the handset is put on the apparatus 7 (Fig. 5, moment t ₆ ), the electronic detector 19 will transmit a signal about this to the control command extraction circuit 14 (Fig. 5, interval t ₆ -t ₇ ), and it will give a reset pulse of negative polarity (Fig. 5, interval t ₇ -t ₈ ). This pulse through the final protected section 6 (Fig. 5c, interval t ₇ -t ₈ ) and the diode 17 will go to the coil 18 of the polarized relay (Fig. 5d, interval t ₇ -t ₈ ), which causes the switching of contacts 13, 15 of the relay the initial position (Fig. 3, moment t ₈ ), while the device will return to its original state - standby mode (Fig. 3, interval t ₈ -t ₉ ).

Thus, while the line is in the end state and the line is open, a section 6 of increased security is formed on the telephone line 4, in which there is no constant voltage. Concerning:
guaranteed there is an obstacle to the signal "HF imposition" on the telephone due to a broken line;
a combined telephone transmitter with line power is guaranteed to stop working due to lack of power;
the combined telephone transmitter with autonomous power supply is guaranteed to go false, switching to broadcast from the line, since the voltage on the line has dropped below a threshold value. If white noise is added to the high security area, the transmitter will broadcast this noise;
for the above reasons, automatic voice recorders connected to the high-security area with all kinds of sensors will go into a false state and begin to expend film and an autonomous power supply;
since the “telephone ear” behaves like a parallel telephone set, the situation with the receipt of ringing signals without subsequent removal of the telephone receiver is correct.

 Thus, the present invention can significantly increase the security of the telephone line from interception of voice information by some types of telephone means of unauthorized receipt of information. Moreover, the protection is guaranteed. In combination with the methods already known, the method described here allows to increase the reliability of protective modules and reduce the likelihood of information interception to a very small value.

Claims (3)

 1. A method of protection against unauthorized listening to conversations in a room between telephone calls using unauthorized access devices using a telephone line as a line for transmitting intercepted voice information, and / or for power, and / or for receiving information about the line status and making decisions to enable the mode of interception of voice information, which consists in blocking these devices of unauthorized access by changing the electrical parameters to the final protected ohm section of the telephone line, characterized in that they automatically control the change in electrical parameters on the final protected section of the telephone line, consisting in the fact that the final protected section of the telephone line passing through the protected room and ending with a standard telephone set is disconnected from the rest of the telephone line outside the protected premises in any place at a time when the telephone line is not used for telephone conversations, and automatically reconnect the end of the protected area with a telephone line during the passage of ringing signals from an automatic telephone exchange or during telephone conversations with a standard telephone set at the initiative of a subscriber or partner calling through an automatic telephone exchange, and then again when negotiations are completed or when ringing signals end disconnect from the telephone line its specified end protected area.  2. A device for protecting against unauthorized listening to conversations in a room between telephone calls, which contains a blocking unit for unauthorized access devices and ensuring the operation of a standard telephone set, characterized in that the blocking unit for unauthorized access devices and ensuring the operation of a regular telephone set is designed as a remote executive a unit installed outside the protected room and containing a switching device connected to the incoming to him a section of the telephone line, and connected to a control unit containing a control command allocation circuit and an electronic activity detector connected to it, connected to a standard telephone set.  3. The device according to claim 2, characterized in that the remote actuating unit contains a rectifier, one input of which is connected to the incoming section of the telephone line through an isolation capacitor, while the output of the rectifier is connected to the coil of a polarized relay of the switching device, and the input of the rectifier is connected to one group mobile contacts of the polarized relay that are connected to the incoming section of the telephone line, and mobile contacts of another group of the polarized relay are connected to the incoming section and through no diode connected for isolation pulse indicative of the switch-on - of a positive polarity, a diode for isolating pulse indicative of the discharge - of negative polarity, the two diodes via the end portion connected to the protected circuit selection control command of the control unit.

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