EP1226661A1

EP1226661A1 - A system and method for monitoring a wiretap

Info

Publication number: EP1226661A1
Application number: EP00966589A
Authority: EP
Inventors: Deok Woo Kim
Original assignee: Woorigisool Inc
Current assignee: Woorigisool Inc
Priority date: 1999-11-05
Filing date: 2000-10-10
Publication date: 2002-07-31
Also published as: KR20010045669A; CN1387705A; KR100335513B1; AU7692000A; WO2001033734A1; JP2003513390A

Abstract

The present invention relates to bugging-device detecting apparatus and method being able to detect not only a bugging device which always operates but also a VOX-type bugging device which operates only when there is sound. This detecting method acquires a frequency spectrum of detected wireless signals within target frequency band, outputs a voice sound, re-acquires a frequency spectrum of wireless signals while the voice sound is being outputted, compares the two spectrums to know whether the two spectrums are the same, and determines whether a hidden listening device is operative around based on the comparison result.

Description

D E S C R I P T I O N

A SYSTEM AND METHOD FOR MONITORING A WIRETAP

1 . Technical Field

The present invention relates to method and apparatus for detecting whether a hidden listening device is active or not.

2. Background Art

A hidden listening device is a kind of a small voice-radio transmitter, which is designed from a wireless microphone. To reduce power consumption, its complex components are replaced with microchips. However, it usually uses an unauthorized frequency band.

A hidden listening device is classified into two categories according to their operating methods. One is a VOX (Voice Operated/Activated Transmission) type, which is operative only when a voice or sound is detected. And, the other is operative at all times. The VOX-type device is prevailing, since the always-operating type can operate for about 48 hours due to limit of power supply.

In addition, A hidden listening device can be classified according to their transmission. One uses wireless and the other uses wired transmission. The former uses high frequency band to transmit eavesdropped voice signal.

Within the band of 10 MHz ~ 2 GHz, the wireless device uses 76 MHz ~ 120 MHz for FM band, 134 MHz ~ 155 MHz for VHF band, and 320 MHz ~ 1200 MHz (mainly, 330 MHz ~ 450 MHz) for UHF. FM or WFM is used as its modulation.

In these days, it is possible to manufacture a hidden listening device such that ts size becomes very small up to a quarter of thumbnail owing to newly-developed technology. With this remarkable reduction m size, anybody who wants to eavesdrop can insert the device into subsistence goods such as watch, telephone, calculator, picture, mirror, and so on. Therefore, such a hidden device can not be discovered with naked eyes. Instead, the device is found laboriously w th a special detecting apparatus .

The primary use of a hidden listening device is to pry into a secret and information of a company or a person illegally. Therefore, such use gives rise to many social and ethnic problems .

Accordingly, several devices to detect these illegal hidαen listening devices have been invented. These bugging detection devices are usually developed through modification of a wireless receiver, a frequency analyzer, or a spectrum analyzer. These devices detect frequency bands of received signals, display it onto a LCD or a monitor, which enables an operator to determine whether there is a frequency band having an unusual intensity.

However, because this method highly depends on the experience and expertise of an operator, it costs too much. Furthermore, this method also has some problems tnat it s sometimes difficult to determine whether there is a hidden listening device due to unknown signals generateα at a detecting time since the detecting work is conducted once or twice.

In addition, this method can not detect a VOX-type hidden listening device since the VOX-type device becomes operative with a presence of voice or sound. To detect VOX-type hidden listening devices, someone should keep on speaking for some time to make VOX-type device operate. This detecting work is very tedious . Furthermore, since most of bugging detection devices operate separately, it s cumbersome to detect whether there is a bugging device or not through keeping on watching a monitor of a bug detecting device, whenever m need.

3. Disclosure of Invention

It is an object of the present invention to provide method and apparatus being able to detect perfectly whether or not there is a bugging device through using pre-stored basic spectrum information as well as generating voice sound from pre-stored voice data, and to deliver the detection result to a remote center. A bugging detection device according to the present invention comprises a tuning means detecting wireless signals by varying a tuning band step by step; an acquisition means obtaining a frequency spectrum of the signals observed by said tuning means; a storage means storing basic frequency-allocation information and basic spectrum information and for storing the frequency spectrum obtained by said acquisition means; a sound generating means outputting sound; and a controlling means controlling said sound generating means to output sound at a pre-specifled time, changing the tuning band of said tuning means, comparing the frequency spectrum obtained by said acquisition means with the basic spectrum information stored m said storage means, and determining whether a hidden listening device is present around. Another bugging detection device according to the present invention comprises the aforementioned tuning means, acquisition means, storage means, sound generating means, controlling means, and a sound detecting means detecting whether there is an outer sound to be possibly eavesdropped, wherein said controlling means compares the frequency spectrums obtained by said acquisition means before and after detection of the outer sound by said sound detecting means and determines whether a hidden listening device is present around based on the result of comparison.

A bugging detection method according to the present invention acquires a frequency spectrum of detected wireless signals, outputs a voice sound, re-acquiring a frequency spectrum of wireless signals detected after the voice sound is outputted, and compares the two acquired frequency spectrums, and determines whether a hidden listening device is present around based on the compared result.

A buggmg-device surveillance system according to the present invention comprises one or more bugging detection devices outputting sound at a preset active operating time, obtaining a frequency spectrum of wireless signals detecteα after the output of sound, determining the presence of a hidden listening device based on the obtained frequency spectrum, and sending the determination result ; and a central server receiving the determination results sent from one or more said bugging detection devices through a network, and displaying the received determination results to notify an operator that a certain area is being eavesdropped. The present bugging detection system ana method can perfectly detect a hidden listening device that always operates, as well as a VOX-type device through generating a voice sound and comparing the detected spectrum with the pre-stored basic spectrum information . In addition, the centralized monitoring system according to the present invention eliminates bothering situations that an operator should continue to monitor a bugging detection device to check the presence of a hidden listening device, ana provides more effective and cheaper way to monitor whether a bugging device has been installed m important or private areas . 4. Brief Description of Drawings

The accompanying drawings, which are included to provide a further understanding of the invention, illustrate the preferred embodiment of this invention, and together with the description, serve to explain the principles of the present invention. In the drawings : FIGS. 1 through 4 depict several networks m which the present bugging detection system may be embodied;

FIG. 5 is a block diagram of a bugging detection device according to the present invention;

FIG. 6 depicts a flowchart embodying a bugging detection method according to the present invention;

FIG. 7 depicts sliced frequency bands and examples of some signal-detected bands;

FIG. 8 is another block diagram of a bugging detection device according to the present invention; FIG. 9 depicts an example of frequency spectrum before and after a voice sound is outputted from the device configured as FIG. 5 or 8; and

FIG. 10 depicts another flowchart embodying a bugging detection method according to the present invention. 5. Modes for Carrying out the Invention

The accompanying drawings illustrate the preferred embodiments of the present invention, and together with the description, serve to explain the principles of the present invention . FIG. 1 depicts an overall network m which the present bugging detection system is embodieα. Th s network comprises a plurality of bugging detection devices lOOn which generate voice sounds, acquire frequency spectrums of detected signals before and after the voice sounds is generated, determine the presence of a hidden listening device through checking the acquired frequency spectrums, and send the determined results to pertinent local servers; local servers 200n, which are connected to grouped bugging detection devices through Local Area Network (LAN) , gather the determined results and send them to a central server via Public Switched Telecommunication Network (PSTN); and the central server 300 displaying the received results onto a monitoring screen 400 and intensively observing whether a hidden listening device is installed m a certain area.

As depicted m FIGS. 2 through 4, the present invention can use serial communication port, for example, RS-232C or Universal Serial Bus (USB) port to connect individual bugging detection devices to a local server and can be configured such that individual bugging detection devices are connected to a monitoring terminal of a security company via discrete DC Output Port.

FIG. 5 is a block diagram of a bugging detection device, which is a component of the network of FIG. 1, according to the present invention, The device of FIG. 5 comprises a tuning unit 10 tuning interested frequency band; an intermediate frequency (IF) converter 20 converting the tuned signal whose band is within some MHz ~ GHz to IF band; an AD converter 30 converting an analog signal into digital data; a ROM 41 pre-stormg a device identification code and necessary program to check the presence of a hidden listening device; a memory 42 for storing basic frequency-allocation and spectrum information, voice source data to help detection of the presence of a hidden listening device, and alarm data to inform that a hidden listening device is detected; a timer 43 notifying a certain set time; a keypad 50; a Liquid Crystal Display (LCD) 60 displaying messages; a DA converter 71 converting the stored digital data to analog signal; a sound generator 70 consisting of an amplifier 72 to output power-amplified analog signal to a speaker Sp; a communication unit 80 sending detection result of a hidden listening device together with the device identification code to a local server (an exclusively-monitoring PC for serial communication, or an exclusive terminal for the joint configuration with a security company) through LAN and receiving control data from a remote server; and a controller 40 changing the tuning band of the tuning unit 10, running the program stored in the ROM 41, and determining whether a hidden listening device has been installed or not.

FIG. 6 depicts a flowchart embodying a bugging detection method according to the present invention, whose particulars will be described hereinafter with referring to drawings of FIGS. 1 and 5.

At first, a user installs the bugging detection device 100 in a suspicious area and sets general operating time as ^λall time' and active operating time as 'partial time' , for example, 9-10 pm through the keypad 50 attached to the device 100. These operating times may be remotely set from a remote server or an exclusive PC. The controller 40 memorizes the set operating times and conducts an usual RF signal monitoring operation during the set general operating time and an active detection operation, in which a voice sound is generated, during the set active operating time. Details of this operation will be served as follows .

The memory 42 stores the basic frequency-allocation information and the basic spectrum information. The basic frequency-allocation information is on common frequency distribution or actually-used frequency bands, which vary each and every region, and is used for scanning frequency bands . The basic spectrum information is spectrum data acquired experimentally before artificial or natural voice sound is generated.

After the device is installed and turned on, the timer 43 keeps track of the current time and the controller 40 checks whether the current time of the timer 43 falls into the preset active operating time or not (S10) .

When the current time does not fall into the active operating time, the controller 40 executes the usual monitoring operation. To do this, the controller 40 carries out a judging process on the presence of a hidden listening device through executing the program stored in the ROM 41. The judging process is conducted step by step as follows.

The tuner 10 passes high frequency signals having a frequency band set by the controller 40, from the signals received through an antenna. The passed high frequency signals are converted into IF signals by the IF converter 20 and are converted into digital data by the AD converter 30.

After the controller 40 determines on the existence of signal components of the tuned frequency band based on the magnitude of the converted digital data, it sets the next tuning band in the tuner 10. According to this procedure, the controller 40 scans whole target frequency band, i.e., 10MHz~2GHz band with referring to the basic frequency- allocation information stored in the memory 42, obtains a frequency spectrum (Sll) using the magnitudes at each frequency band, and stores spectrum data as form depictec in FIG. 7.

FIG. 7 depicts a spectrum example obtained with two slice bandwidths, one being lOKHz for below 450MHz and the other being 30KHz for above 450MHz. In addition, according to prescribed scanning priority, the oand of 320MHz ~ 450MHz, 135MHz~i55MHz, and 450MHz ~ 1.2GHz are sequentially scanneα. The controller 40 compares the basic spectrum information stored in the memory 40 with the obtained frequency spectrurr (S12), checks whether signal-detected bands are all identical to signal-existing bands of the basic spectrum information, and determines whether a hidden listening is operative at present or not (S13) .

If at least one of the signal-detected bands is not identical, the controller 40 controls the sound generator

70 to output an alarm sound, or extracts warning sound data, for example, siren data stored m the memory 42 and outputs it to the speaker Sp after processing it with the DA converter

71 and the amplifier 72, so that someone nearby the device lOOn is informed that a hidden listening is operative around and takes an appropriate action such as searching for a hidden listening device. In addition, the controller 40 sends the detection result and the device identification code stored m the ROM 41 to tne pertinent local server 200n or an upper device through a connected LAN. The above-explained detection operation is conducted continuously for the set general operating time .

The local server 200n which is connected to a plurality of bugging detection devices lOOn through LAN, gathers data from the individual detection device lOOn, makes connection with the central server 300 periodically through PSTN, and sends the gathered data to the central server 300 through a connected PSTN (S14) and a gateway, if required.

The central server 300 displays the device identif cation codes and the detection results received throuqh PSTN on the monitoring screen 400, and generates warning signal m case that at least one of the detection results is indicative of presence of a hidden listening device, so that an administrator of the central server 300 can ascertain that there is an operating hidden listening device installed around a detection device distinguished by the device identification code. This procedure and configuration enables central surveillance for illegal hidden listening. FIG. 8 is another block diagram of a bug detecting device according to the present invention. The device of FIG. 8 further comprises, besides the elements of FIG. 5, an input amplifier 73 amplifying analog audio signals from a microphone Mic up to appropriate level; an AD converter 74 (in some cases, the AD converter 30 can be used) converting the amplified analog audio signal into digital data.

In the bugging detection device configured as FIG. 8, the controller 40 continues to check the existence of voice input from the microphone based on the digital data acquired from the input amplifier 73 and the AD converter 74 for the set general operating time, while measuring the frequency spectrum periodically as described above.

If an outer voice or sound from the microphone is detected during the checking operation, the controller 40 compares the frequency spectrums before and after detection of outer sound and determines whether a hidden listening device is operative or not based on the comparison result. The determination is done only after confirming the existence of outer voice which might be eavesdropped. In determination, the controller 40 may also make decision by comparing the pre-stored basic spectrum information with that acquired after an outer signal is detected. The action to be taken after decision-making is same as described earlier.

While conducting the above-explained detecting operation, the controller 40 also checks whether the current time being taken track of by the timer 43 falls into the set active operating time. If the current time belongs to the set active operating time, the controller 40 conducts an active detecting operation as follows.

The controller 40 outputs a voice sound by controlling the sound generator 70, or extracts the sound data - recorded human voice is more desirable - pre-stored in the memory 42, and converts the digital voice data to analog signal through the DA converter 71 and the output amplifier 72. The analog signal from the sound generator 70 is outputted through the speaker Sp (S22) .

While voice sound is being outputted through the speaker Sp for a specific time, the controller 40 measures a frequency spectrum, as described earlier, for all signals detected by the tuner 10 (S23) . After the frequency spectrum is acquired, the controller 40 compares the frequency spectrum obtained while voice sound is being outputted with that obtained prior to the output of voice sound (S24) , and determines whether there is a hidden listening device or not based on whether the signal-detected bands are identical in the two obtained spectrums (S30) . This determination is based on the fact that the two frequency spectrums obtained before and after the output of voice sound become different each other as depicted in FIG. 9, since a hidden listening device starts to transmit bugged sounds in wireless through an illegal band with the start of voice output and that the transmitted signal from the hidden listening device installed some distance apart from the detecting device is detectable. If both frequency spectrums are not identical, that is, there is a signal component which is not in the frequency spectrum acquired prior to the output of voice, however, is in the spectrum obtained after the output of voice, the controller 40 considers that there is a hidden listening device around (S40) , outputs an alarming voice or sound by- driving the sound generator 70 as described earlier, or generates a warning signal such as siren, and sends reporting data indicative of detection of a hidden listening device together with the device identification code pre-stored in the ROM 41 to the pertinent local server 200n or an upper device through the connected LAN. This active detecting operation is conducted periodically every active operating time, for example, 9~10 pm. Even m the case that both frequency spectrums are identical, there may be an odd that a hidden listening device is not VOX type but always-operating type. Therefore, the controller 40 snould compare the frequency spectrum obtained before or after the output of voice sound with the basic spectrum information, which is stored m the memory 42, of all the receivable signal components m that installed area (S31), and determine the presence of a hidden listening device based on the comparison (S32) . The procedures following the determination are same as describeα earlier. FIG. 10 depicts another flowchart embodying a bugging detection method according to the present invention, whose particulars will be described w th referring to drawings of FIGS. 1 and 5. The method of FIG. 10 regards procedures conducted when the current time being kept track of by the timer 43 belongs to the set active operating time .

Instead of determining the presence of a hidden listening device base on the comparison of the two spectrums obtained before and after the output of sound, the controller 40 acquires a frequency spectrum of all signals tuned by the tuner 10 (S52) after outputting voice sound (S51), compares the obtained spectrum with the basic spectrum information stored m the memory 42 (S53) , and determines on the presence of a hidden listening device based on the compared result (S54) . The post procedure (S55) after this determination is same as described earlier.

In the embodiment depicted m FIG. 10, the reason why voice sound is generated prior to the acquisition of frequency spectrum is to detect a VOX-type hidden listening device.

In the above-explained embodiments, the keypad 50 can be replaced with a button switch, i.e., a reset button so that it has minimum size and function. The other functions are execute through a remote command from a server or an exclusive PC. In addition, the LCD 60 can be also replaced with a LED so that it has minimum size and function. For this case, a graphical display such as frequency spectrum is drawn on an outer apparatus such as a server or an exclusive PC.

The bugging detection system according to the present invention can be embodied with a conventional bugging detection device. In this case, a conventional bugging detection device should be equipped with a communication element so that the detection result is transferred via the communication element to a remote monitoring device after the presence of a hidden listening device is detected, thereby constructing intensive central surveillance system. The invention may be embodied m other specific forms without departing from the sprit or essential characteristics thereof. The present embodiments are therefore to be considered m all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore mtendeα to be embraced therein.

Claims

C L A I M S

1. A method for detecting a hidden listening device, comprising the steps of:

(a) acquiring a frequency spectrum of detected wireless signals;

(b) outputting a voice sound;

(c) re-acquiring a frequency spectrum of wireless signals detected after the voice sound is outputted; and

(d) comparing the two frequency spectrums acquired at said steps (a) and (c), and determining whether a hidden listening device is present based on the compared result.

2. A method set forth m claim 1, wherein said steps (a) to (c) are executed periodically every a preset time.

3. A method set forth m claim 1, wherein said step (d) further compares one of the acquired frequency spectrums with pre-stored basic spectrum information if the compared result indicates that the two frequency spectrums are same, and determines the presence of a hidden listening device.

4. A method set forth m one of claims 1 to 3, wherein said step (b) outputs the voice sound through converting pre- stored source data into sound signal.

5. A method set forth m one of claims 1 to 4, further comprising the step of choosing a scanning frequency band based on pre-stored basic frequency-allocation information prior to said step (a) .

6. A method for detecting a hidden listening device, comprising the steps of:

(a) outputting a voice sound;

(b) acquiring a frequency spectrum of wireless signals detected after the voice sound is outputted; and (c) comparing the acquired frequency spectrum with pre-stored basic spectrum information and determining whether a hidden listening device is present based on the compared result.

7. A method set forth in claim 6, wherein said step (a) outputs the voice sound through converting pre-stored source data into sound signal.

8. A method for detecting a hidden listening device, comprising the steps of: (a) acquiring a frequency spectrum of detected wireless signal ;

(b) checking whether there is an outer sound or not; and

(c) comparing the acquired frequency spectrum with another frequency spectrum acquired after it is confirmed that there is an outer sound, and determining whether a hidden listening device is present based on the compared result.

9. A method set forth in claim 8, further comprising the step of choosing a scanning frequency band based on pre- stored basic frequency-allocation information prior to said step (a) .

10. An apparatus for detecting a hidden listening device, comprising : a tuning means detecting wireless signals by varying a tuning band step by step; an acquisition means obtaining a frequency spectrum of the signals observed by said tuning means; a storage means storing basic frequency-allocation information and basic spectrum information, and for storing the frequency spectrum obtained by said acquisition means; a sound generating means outputting sound; and a controlling means controlling said sound generating means to output sound according to a pre-specified time, changing the tuning band of said tuning means, comparing the frequency spectrum obtained by said acquisition means w th the oasic spectrum information stored m said storage means, and determining whether a hidden listening device is present baseα on the compared result.

11. An apparatus set forth m claim 10, further comprising a sound detecting means detecting whether there is an outer sound to be possibly eavesdropped, wherein said controlling means compares the frequency spectrums obtained by said acquisition means before and after detection of the outer sound by said sound detecting means, and determines whether a hidden listening device is present baseα on the result of comparison .

12. An apparatus set forth m claim 10, wherein said controlling means controls sa d sound generating means to generate a warning sound if it is confirmed that the spectrum comparison result is indicative of the presence of a hidden listening device.

13. An apparatus set forth m claim 10, further comprising a communication means transmitting and receiving data to/from an external apparatus, wherein said controlling means sends the determined result on the presence of a hidden listening device together with a device identification code further stored m said storage means through said communication means .

14. An apparatus set forth m one of claims 10 to 13, wherein said storage means further stores sound source data, and said generating means extracts the sound source data and outputs sounα through converting the sounα source data into sound signal .

15. A buggmg-device surveillance system, comprising: one or more bugging detection devices outputting sound at a preset active operating time, obtaining a frequency spectrum of wireless signals detected after the output of sound, determining the presence of a hidden listening device based on the obtained frequency spectrum, and sending the determination result; and a central server receiving the determination results sent from one or more said bugging detection devices through a network, and displaying the received determination results to notify that a certain area is being eavesdropped.

16. A buggmg-device surveillance system, comprising: one or more bugging detection devices obtaining a frequency spectrum of wireless signals, determining whether an outer voice is eavesdropped based on the obtained frequency spectrum, and sending the determination result through an internal communication means; and a central server receiving the determined results sent from one or more said bugging detection devices through a network, and displaying the received determination results to notify that a certain area is being eavesdropped.

17. A buggmg-device surveillance system, comprising: one or more bugging detection devices either outputting sound at a preset active operating time, obtaining a frequency spectrum of wireless signals detected after the output of sound, and determining the presence of a hidden listening device based on the obtained frequency spectrum, or checking whether there is an outer sound, comparing frequency spectrums obtained before and after it is confirmed that there is an outer sound, and determining the presence of a hidden listening device baseα on the comparison result, and sending the determination result; and a central server receiving the determination results sent from one or more said bugging detection devices through a network, and displaying the received determination results to notify that a certain area is being eavesdropped.