GB2366866A

GB2366866A - Acoustic system for sensing the presence of a person in the vacinity of a computer

Info

Publication number: GB2366866A
Application number: GB0108555A
Authority: GB
Inventors: Itzhak Pomerantz; Shmuel Miller
Original assignee: Aliroo Ltd
Current assignee: Aliroo Ltd
Priority date: 2000-04-06
Filing date: 2001-04-05
Publication date: 2002-03-20
Also published as: DE10117240A1; GB0108555D0

Abstract

A system for detecting the presence of a non-stationary object in the vicinity of a computer 10 comprising a first audio transducer 14 for providing a sending signal, a second audio transducer 16 for receiving signals in the vicinity of the computer, and detection circuitry to analyse the received signals and determine the presence of a non- stationary object in the vicinity of the computer. The system is designed to be used both for energy saving by turning the monitor off if a user is absent, or as a security feature by locking the workstation if the user is absent.

Description

2366866

FIELD OF THE INVENTION

The present invention relates to computer security generally and more 5 particularly to detection of the presence of a person in the vicinity of a computer.

BACKGROUND OF THE INVENTION

Conventional computer security is often password based, in that the computer 10 user is required to enter a secret password to be enabled to operate the computer.

The password is often required to enable a user to operate certain software or access certain information. Often, other computer functions are not password protected. Thus, although certain computer functions are protected by password security, an unscrupulous user may nevertheless cause damage to the computer or its 15 software by operating the computer in a manner which is not password protected.

Furthermore, with the advent of increasingly more sophisticated hacking techniques, requiring the use of a password is not always sufficient to prevent unauthorized persons from operating a computer, such as a personal computer. In certain cases, skilled hackers are able to bypass the password security features of a 20 computer.

Aside from password security, the use of biometric inputs and hardware tokens for security are also known and suffer from similar limitations.

There are known a great variety of intrusion detection techniques, including, inter alia, those based on thermal, acoustic, RF and visible light sensing.

SUMMARY OF THE INVENTION

The present invention seeks to provide a computer-based physical access security system, particularly suitable for personal computers, which is relatively 30 inexpensive and easy to use and install and which provides protection against unauthorized physical access to a computer and the vicinity thereof. The present invention also provides a system and method for detecting the presence of a non-stationary object in the vicinity of a personal computer as well as a personal computer system operative for detecting the presence of a non-stationary object in the 35 vicinity thereof The present invention may also be employed for detection of the absence of a person in the vicinity of a computer, such as for the purpose of automatic shut down of the computer or log-off from the computer after a predetermined time interval.

I There is thus provided in accordance with a preferred embodiment of the present invention a system for detecting the presence of a non-stationary object in the vicinity of at least one personal computer, the system including:

at least one first audio transducer associated with the at least one personal 5 computer and receiving driving inputs therefrom; at least one second audio transducer associated with the at least one personal computer and providing received signal inputs thereto; transmitter circuitry, at least associated with the at least one personal computer, for providing the driving inputs to the at least one first audio transducer, 10 thereby causing it to generate audio energy in the vicinity of the at least one personal computer; receiver circuitry, at least associated with the at least one personal computer, for receiving the received signal inputs from the at least one second audio transducer, representing audio signals received from the vicinity of the at least one personal 15 computer, including reflections of audio energy generated by the at least one first audio transducer; and detection circuitry, at least associated with the at least one personal computer for determining whether a non-stationary object has been detected based on an analysis of the received signal outputs and the driving inputs.

20 There is also provided in accordance with a preferred embodiment of the present invention a method for detecting the presence of a non-stationary object in the vicinity of a personal computer, the method including:

causing circuitry, at least associated with the at least one personal computer to provide driving inputs to at least one audio transducer, thereby causing it to generate 25 audio energy in the vicinity of the at least one personal computer; causing circuitry, at least associated with the at least one personal computer to receive received signal inputs from the at least one audio transducer, representing audio signals received from the vicinity of the at least one personal computer, including reflections of audio energy generated by the at least one audio transducer 30 from objects in the vicinity; and determining whether an object has been detected based on an analysis of the received signal outputs and the driving inputs.

There is additionally provided in accordance with a preferred embodiment of the present invention a personal computer system operative for detecting the presence 35 of a non-stationary object in the vicinity thereof and including:

a personal computer; at least one first audio transducer associated with the at least one personal computer and receiving driving inputs therefrom; 2 at least one second audio transducer associated with the at least one personal computer and providing received signal inputs thereto; circuitry, at least associated with the at least one personal computer, for providing the driving inputs to the at least one first audio transducer, thereby causing 5 it to generate audio energy in the vicinity of the at least one personal computer; circuitry, at least associated with the at least one personal computer, for receiving the received signal inputs from the at least one second audio transducer, representing audio signals received from the vicinity of the at least one personal computer, including reflections of audio energy generated by the at least one audio 10 transducer from objects in the vicinity; and circuitry, at least associated with the at least one personal computer for determining whether a non-stationary object has been detected based on an analysis of the received signal outputs and the driving inputs.

There is further provided in accordance with a preferred embodiment of the 15 present invention, for use in a method for detecting the presence of a non-stationary object in the vicinity of a personal computer, software installable in the at least one personal computer and having the following functionality when installed; audio energy generating functionality, causing circuitry, at least associated with the at least one personal computer to provide driving inputs to at least one audio 20 transducer, thereby causing it to generate audio energy in the vicinity of the at least one personal computer; reflected audio energy receiving functionality, causing circuitry, at least associated with the at least one personal computer to receive received signal inputs from the at least one audio transducer, representing audio signals received from the 25 vicinity of the at least one personal computer, including reflections of audio energy generated by the at least one audio transducer from objects in the vicinity; and analysis functionality, determining whether a non-stationary object has been detected based on an analysis of the received signal outputs and the driving inputs.

The at least one personal computer may include a single personal computer or 30 plural personal computers.

Plural personal computers may have overlapping regions of protection in which a non-stationary object may be detected by the detection circuitry.

Plural personal computers may cooperate to detect non-stationary objects.

Presence/absence indicating circuitry may be provided for receiving an input 35 from the detection circuitry for indicating at least one of the presence and absence of a person in the vicinity of the at least one personal computer.

The presence/absence indicating circuitry preferably provides output indications of both presence and absence of a person in the vicinity of the at least one 3 personal computer.

Preferably, the system is embodied substantially entirely in software installed in at least one existing personal computer equipped with at least one audio transducer.

The software may be installed on multiple computers located in mutually 5 disparate locations and also including a monitoring server which correlates outputs of the detection circuitry thereby to produce an output indication of at least one of absence and presence of persons in the vicinities of the multiple computers. The output indication is preferably a mutually time-coordinated indication of both absence and presence of persons in the vicinities of the multiple computers.

10 In accordance with a preferred embodiment of the present invention, there is provided anti-hacking warning functionality which is operative to sense the receipt of keystrokes purportedly coming from a computer in respect of which the detection circuitry indicates the absence of a non-stationary object in the vicinity thereof and to provide a hacking warning in response thereto.

15 Additionally in accordance with a preferred embodiment of the present invention, there is provided client computer user interface disabling facility operative in response to indicated absence of a person from the vicinity of a computer for at least a predetermined time.

Further in accordance with a preferred embodiment of the present invention, 20 there is provided client computer user interface enabling facility operative in response to indicated presence of an authorized person from the vicinity of a computer.

Still further in accordance with a preferred embodiment of the present invention, there is provided guard tour logging functionality which is operative to sense the time relationship of the presence of a person sequentially in the vicinities of 25 multiple computers in a facility. Preferably, the guard tour logging functionality includes exception notification functionality operative to provide an indication of departure from a pre-estabiished guard round schedule.

Additionally in accordance with a preferred embodiment of the present invention, there is provided automatic infrastructure operation/termination 30 functionality which is operative to operate infrastructure facilities in response to output indications of the presence and absence of persons in vicinities of personal computers.

In one embodiment of the present invention, at least one of the at least one first audio transducer and the at least one second audio transducer are selectably 35 positionable with respect to the personal computer.

Preferably, the audio energy is in the form of a chirp. Different ones of the plural computers preferably have different characteristic chirps.

Preferably, the detection circuitry is operative to distinguish between audio 4 energy reflected from objects located respectively within and outside at least one protected region.

5 BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which:

Fig. I is a simplified pictorial illustration of a preferred embodiment of the 10 present invention; Fig. 2 is a simplified functional block diagram of the embodiment of Fig. 1; Figs. 3A, 3B and 3C are waveforms useful in understanding the operation of a 15 preferred embodiment of the present invention; Fig, 4 is an illustration of a signal autocorrelation function useful in understanding a desired property of waveforms suitable for use in a preferred embodiment of the present invention; Fig. 5 is a simplified flow chart illustrating operation of a preferred embodiment of the present invention; Fig. 6 is a simplified diagram illustrating one embodiment of absence/presence 25 functionality provided in accordance with a preferred embodiment of the present invention; Figs. 7A & 7B taken together are a simplified flow chart illustrating the functionality of Fig. 6; Fig. 8 is a simplified diagram illustrating anti-hacking functionality provided by absence/presence functionality in accordance with a preferred embodiment of the present invention; 35 Fig. 9 is a simplified flow chart illustrating the functionality of Fig. 8; Fig. 10 is a simplified diagram illustrating selection of the location of a region of protection surrounding a computer in accordance with a preferred embodiment of the present invention; Fig. I I is a simplified pictorial illustration of an arrangement of multiple computers having mutually overlapping regions of protection; Fig. 12 is a simplified diagram illustrating a distribution in time and frequency of multiple chirp transmissions useful by multiple computers whose locations are such that their transmissions may produce interference therebetween; 10 Fig. 13 is a simplified functional block diagram illustrating the operation of a multiple computer protection system embodying the functionality of Fig. 11; Fig. 14 is a simplified pictorial illustration of an arrangement wherein multiple computers cooperate in detection of a moving object; and Fig. 15 is a simplified functional block diagram illustrating the operation of a computer protection system embodying the functionality of Fig. 14.

20 DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Reference is now made to Fig. 1, which is a simplified pictorial illustration of a preferred embodiment of the present invention.

As illustrated in Fig. 1, there is provided in accordance with a preferred embodiment of the present invention a system and method for detecting the presence 25 of a non-stationary object in the vicinity of a personal computer. Preferably the system, as illustrated in Fig. I includes a personal computer 10, which may be any suitable conventional personal computer which is equipped with a sound card 12, at least one speaker 14 and at least one microphone 16. In a less preferred, but possible configuration, the personal computer may employ only a single audio transducer for 30 both sound generating and sound receiving functionalities.

In accordance with a preferred embodiment of the invention, the personal computer is loaded with software 20 having the following functionality:

audio energy generating functionality, causing circuitry, at least associated with the personal computer, to provide driving inputs to at least one audio transducer, 35 such as a speaker 14, thereby causing it to generate audio energy in the vicinity of the personal computer; reflected audio energy receiving functionality, causing circuitry, at least associated with the personal computer to receive received signal inputs from the at 6 least one audio transducer, such as microphone 16, representing audio signals received from the vicinity of the personal computer, including reflections of audio energy generated by the at least one audio transducer from objects in the vicinity; and analysis functionality, determining whether a non-stationary object has been 5 detected based on an analysis of the received signal outputs and the driving inputs.

In accordance with a preferred embodiment of the present invention, the software 20 allows the user of the personal computer to determine a region of protection in three dimensions, measured from speaker 14 and microphone 16, within which reflections will be received and employed in analysis. This selectable region is 10 shown symbolically as an outline 22 in Fig. 1.

In the embodiment of Fig. 1, including a single speaker and a single microphone, a maximum range of protection has one focus at speaker 14 and another focus at microphone 16. Only if the microphone and the speaker are at the same location, does the maximum range protection reduce to a sphere. Objects within the 15 region of protection designated by outline 22 will be sensed by the system and objects outside the region of protection will not be sensed. The region of protection may be shorter than the maximum range of protection in some directions, due to limited sensitivity of the microphone and other elements in the system.

Reference is now made to Fig. 2, which is a simplified functional block 20 diagram of the embodiment of Fig. 1. As seen in Fig. 2, the circuitry of the personal computer 10 (Fig. 1) preferably includes a sound pulse generator 30, which is controlled by software 20 (Fig. 1) for operating sound card 12 (Fig. 1) to provide a sound generation output to at least one speaker 14 (Fig. 1).

Microphone 16 (Fig. 1) receives sound reflections from objects, some of 25 which are within a selected or predetermined region of protection, represented by outline 22 (Fig. 1) and provides electrical signals corresponding thereto to sound card 12. Outputs representing both the sound generation output and the sound reflection input are stored separately in a sound file storage facility 32 and are separately filtered by respective filters 34 and 36.

30 The filtered outputs are analyzed preferably using cross correlation functionality 38 to provide a cross correlation output, which is stored in a storage facility 40 and then analyzed and compared with recently stored cross correlation outputs, preferably in near real time by weighted filtering functionality 42, in order to determine whether a moving object has been detected, and if so, whether detection of 35 an object of predetermined significance has occurred.

Fig. 3A illustrates one preferred type of sound output from speaker 14, having fixed frequency and amplitude. Fig. 3B shows an alternative type of sound output from speaker 14. This pulse is a linear, frequency modulated pulse, and is normally 7 preferred over the pulse of Fig. 3A.

Fig, 3C illustrates another preferred type of sound output from speaker 14, having a generally sinusoidal configuration of increasing frequency and rising and falling amplitude. This sound output provides a low sidelobe distribution in 5 autocorrelation, as illustrated in Fig. 4, thus avoiding possible masking of reflections from small objects within a protected region, which might result from the presence of high sidelobes.

Reference is now made to Fig. 5, which is a simplified flow chart illustrating operation of a preferred embodiment of the present invention. As seen in Fig. 5, when 10 a user is logged off from a computer and the client computer user interface is accordingly disabled, the presence detection functionality of the present invention determines whether a moving object of predetermined characteristics is present in the vicinity of the computer. If such an object is detected, a determination is made as to whether that object is an authorized person and, if so, that person may be 15 automatically logged on to the computer and the client computer user interface is enabled. If the object is not an authorized person, an intrusion response may be provided.

Additionally in accordance with a preferred embodiment of the present invention, when an authorized person is logged on and the client computer user 20 interface is thus enabled, the presence detection functionality of the present invention becomes operative, preferably upon the sensed absence of user initiated computer activity, to determine whether a person is present in the vicinity of the computer. If not, the computer may automatically disable the client computer user interface.

Reference is now made to Fig. 6, which is a simplified diagram illustrating 25 one embodiment of absence/presence functionality provided in accordance with a preferred embodiment of the present invention. Fig. 6 illustrates a typical multi-room office 50 including a plurality of computers 52, designated A - F, each operative, in accordance with a preferred embodiment of the present invention to provide an output indication of the presence and absence of a moving object in the vicinity thereof.

30 These indications, designated by reference numeral 54, are preferably provided to a server, providing a visible record of the absence and presence of a moving object, such as a person, in the vicinity of each computer on the same time line.

It can be readily seen that from such inforination, assumptions can be made as to entry of persons normally in the vicinity of one computer into the vicinity of 35 another computer, as indicated in dashed lines and designated by reference numeral 58. There it can be readily visualized that a person usually in the vicinity of computer E has temporarily moved to the vicinity of computer F.

Reference is now made to Figs. 7A & 7B, which taken together are a 8 simplified flow chart illustrating the functionality of Fig. 6. As seen in Fig. 7A, similarly to that shown in Fig. 5, when a user is logged off from a computer and the client computer user interface is accordingly disabled, the presence detection functionality of the present invention determines whether a person is present in the 5 vicinity of the computer.

If a person is detected, a determination is made as to whether that person is an authorized user of the computer and, if so, the client computer user interface is enabled and a monitoring server is notified of a valid presence in the vicinity of the computer. If the object is not an authorized person, an intrusion response may be 10 provided and the monitoring server may be notified of an invalid presence.

Additionally in accordance with a preferred embodiment of the present invention, when an authorized person is logged on and the client computer user interface is thus enabled, the presence/absence detection functionality of the present invention becomes operative, preferably upon the sensed absence of user initiated 15 computer activity, to determine whether a person is present in the vicinity of the computer. If not, the computer may automatically disable the client computer user interface. In such a case, the monitoring server is notified that the computer is unattended.

Turning to Fig. 713, it is seen that the monitoring server records the 20 aforementioned notifications. It may provide various types of intrusion responses including, for example:

alert a security officer enable a security officer to listen to sounds in the vicinity of the computer via the computer microphone; 25 enable a security office to converse with a person in the room via the computer speaker and microphone; turn on lights, cameras, video recorders or other security related devices; and automatically dial a telephone number to alert others.

The monitoring service may also provide various types of absence responses 30 including, for example:

turning off lights and air-conditioning in the vicinity of the computer; and provide an alert in the case of unauthorized or unexplained absence.

The monitoring computer may also provide various reports including, for example:

35 a detailed log of events; an indication of unusual events as per predetermined criteria selected by the user; an indication of correlations between presence and absence; 9 guard tour reports based on sensed presence of a guard wittLin the vicinities of plural computers; and exceptional events in guard tours.

Reference is now made to Figs. 8 & 9, which illustrate anti-hacking 5 functionality enabled by the provision of absence/presence functionality in accordance with a preferred embodiment of the present invention, It is known to hack into a client's network server 60 from a hacker's computer 62 by emulating keystrokes in one of the computers 64 in the network connected to server 60. In accordance with a preferred embodiment of the invention, presence/absence monitoring functionality is 10 provided to the computers 64 in the network in order to notify a monitoring server when a client computer is unattended. As seen in Fig. 9, when the server 62 receives what appear to be keystrokes from a client that is indicated to be unattended, a hacking alert is provided.

Reference is now made to Fig. 10, which is a simplified diagram illustrating 15 selection of the location of a region of protection surrounding a computer in accordance with a preferred embodiment of the present invention. Fig. 10 illustrates graphically that a microphone 70 and a speaker 72 may be selectably positioned relative to a computer 74 in order to selectably define the configuration of a region of protection 76 thereabout.

20 Reference is now made to Fig. 11, which is a simplified pictorial illustration of an arrangement of multiple computers 80, 82 and 84 which are located sufficiently close to each other such that transmissions of one of them can be detected by a microphone on another. The arrangement of Fig. I I has the potential difficulty that a microphone 92 of one computer, such as computer 82, may receive both direct and 25 reflected transmissions from other computers, such as computers 80 and 84. This difficulty is overcome in accordance with the present invention by providing the audio output of each computer with a different characteristic chirp, thus allowing a computer, such as computer 84 to distinguish chirps transmitted by it from those transmitted by other computers. Additionally by randomizing the pulse repetition 30 interval and pre-checking for collisions, the probability of overlap in received chirps is reduced.

Fig. 12 is a simplified diagram illustrating a distribution in time and frequency of multiple chirp transmissions useful by multiple computers having mutually overlapping regions of protection as in the embodiment of Fig. 11.

35 Reference is now made to Fig. 13, which is a simplified functional block diagram illustrating the operation of at least one computer in a multiple computer protection system embodying the functionality of Fig. 11. A frequency generator 100 provides frequency inputs, representing start and end frequencies of a chirp, to a chirp generator 102 which generates a chirp in accordance therewith, which is characteristic of a given computer. The chirp is stored in a chirp file storage facility 104 and is supplied to a chirp D/A converter 106 which also receives a trigger input from a collision avoidance listening circuit 108, which, in turn, receives an input from a 5 random pulse repetition circuit 110. The collision avoidance listening circuit 108 only permits chirp transmission when no chirp is heard immediately prior to the transmission. The chirp D/A converter 106 provides an output to an audio transducer 112, thus producing an outgoing chirp transmission. Incoming chirp echoes as well as the outgoing chirp transmission are received at an audio transducer 114 and supplied 10 to signal processing functionality 116 which also receives inputs from chirp storage file 104 and which provides an indication of the presence or absence of a moving object in the vicinity of computers 80, 82 and 84.

Reference is now made to Fig. 14, which is a simplified pictorial illustration of an arrangement wherein multiple computers cooperate in detection of a moving 15 object. As distinguished from the embodiment of Figs. 11, 12 and 13, here multiple computers, here shown typically as two computers 120 and 122, cooperate to detect persons or other moving objects. In this embodiment, one computer, such as computer 120, transmits a chirp pulse and another computer, such as computer 122, receives echoes of the transmitted chirp pulse and analyzes them to detect moving 20 objects in the vicinity of computers 120 and 122. It is appreciated that in this embodiment of the present invention, no interaction is required between computers and 122, inasmuch as the transmitted chirp can be stored in the receiving computer for reference and a trigger for detection of a reflected chirp can be derived from the received signal itself.

25 As seen additionally in Fig. 15 the transmitted chirp, indicated by reference numeral 130, has a relatively large filtered cross-correlation amplitude and narrow duration, while the reflected chirp Arithin a region of protection, indicated by reference numeral 132, has a relatively low amplitude and long duration. The relevant range, representing the region of protection, is defined by a time duration 30 measured from the receipt of the transmitted chirp, thus excluding other, irrelevant reflected chirps, such as that identified by reference numeral 134.

It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and describedhereinabove. Rather the scope of the present invention includes both combinations and subcombinations of 35 the various features described hereinabove as well as variations and modifications which would occur to persons skilled in the art upon reading the specification and which are not in the prior art.

Claims

1. A system for detecting the presence of a non-stationary object in the vicinity of at least one personal computer, the system comprising:

5 at least one first audio transducer associated with the at least one personal computer and receiving driving inputs therefrom; at least one second audio transducer associated with the at least one personal computer and providing received signal inputs thereto; transmitter circuitry, at least associated with the at least one personal io computer, for providing said driving inputs to said at least one first audio transducer, thereby causing it to generate audio energy in the vicinity of the at least one personal computer; receiver circuitry, at least associated with the at least one personal computer, for receiving said received signal inputs from said at least one second audio 15 transducer, representing audio signals received from the vicinity of the at least one personal computer, including reflections of audio energy generated by said at least one first audio transducer; and detection circuitry, at least associated with the at least one personal computer for determining whether a non-stationary object has been detected based on an 20 analysis of said received signal outputs and said driving inputs.

2. A system according to claim I and wherein said at least one personal computer comprises a single personal computer.

25

3. A system according to claim I and wherein said at least one personal computer comprises plural personal computers.

4.

4. A system according to claim 3 and wherein said plural personal computers have overlapping regions of protection in which a non-stationary object may be 30 detected by said detection circuitry.

5, A system according to claim 4 and wherein said plural personal computers cooperate to detect non-stationary objects.

35 6. A system according to claim I and also comprising presence/absence circuitry receiving an input from said detection circuitry for indicating at least one of the presence and absence of a person in the vicinity of said at least one personal computer.

12 7. A system according to claim I and wherein said presence/absence circuitry provides output indications of both presence and absence of a person in the vicinity of said at least one personal computer.

8. A system according to claim I and wherein said system is embodied substantially entirely in software installed in at least one existing personal computer equipped with at least one audio transducer.

10 9. A system according to claim 8 and wherein said software is installed on multiple computers located in mutually disparate locations and also comprising a monitoring server which correlates outputs of said detection circuitry thereby to produce an output indication of at least one of absence and presence of persons in the vicinities of said multiple computers.

M A system according to claim 8 and wherein said output indication is a mutually time-coordinated indication of both absence and presence of persons in the vicinities of said multiple computers.

20 11. A system according to claim I and also including anti-hacking warning functionality which is operative to sense the receipt of keystrokes purportedly coming from a computer in respect of which said detection circuitry indicates the absence of a non-stationary object in the vicinity thereof and to provide a hacking warning in response thereto.

12. A system according to claim 7 and including a client computer user interface disabling facility operative in response to indicated absence of a person from the vicinity of a computer for at least a predetermined time.

30 13. A system according to claim 7 and including a client computer user interface enabling facility operative in response to indicated presence of an authorized person from the vicinity of a computer.

14. A system according to claim I and also including guard tour logging 35 functionality which is operative to sense the time relationship of the presence of a person sequentially in the vicinities of multiple computers in a facility.

15. A system according to claim 14 and wherein said guard tour logging 13 functionality includes exception notification functionality operative to provide an indication of departure from a pre-established guard round schedule.

16. A system according to claim I and also including automatic infrastructure 5 operation/termination functionality which is operative to operate infrastructure facilities in response to output indications of the presence and absence of persons in vicinities of personal computers.

17. A system according to claim 1 and wherein at least one of said at least one 10 first audio transducer and said at least one second audio transducer are selectably positionable with respect to said personal computer.

18. A system according to claim 1 and wherein said audio energy is in the form of a chirp.

19. A system according to claim 3 and wherein said audio energy is in the forin of a chirp and different ones of said plural computers have different characteristic chirps.

20. A system according to claim I and wherein said detection circuitry is 20 operative to distinguish between audio energy reflected from objects located respectively within and outside at least one protected region.

21. A method for detecting the presence of a non-stationary object in the vicinity of a personal computer, the method comprising:

25 causing circuitry, at least associated with the at least one personal computer to provide driving inputs to at least one audio transducer, thereby causing it to generate audio energy in the vicinity of the at least one personal computer; causing circuitry, at least associated with the at least one personal computer to receive received signal inputs from said at least one audio transducer, representing 30 audio signals received from the vicinity of the at least one personal computer, including reflections of audio energy generated by said at least one audio transducer from objects in said vicinity; and determining whether an object has been detected based on an analysis of said received signal outputs and said driving inputs.

22. A method according to claim 21 and wherein said at least one personal computer comprises a single personal computer.

14 23. A method according to claim 21 and wherein said at least one personal computer comprises plural personal computers.

24. A method according to claim 23 and wherein said plural personal computers 5 have overlapping regions of protection in which an object may be detected by said detection circuitry.

25. A method according to claim 24 and wherein said plural personal computers cooperate to detect non-stationary objects.

26. A method according to claim 21 and also comprising presence/absence functionality including indicating at least one of the presence and absence of a person in the vicinity of said at least one personal computer.

15 27. A method according to claim 21 and also comprising indicating both presence and absence of a person in the vicinity of said at least one personal computer.

28, A method according to claim 21 and wherein said method is embodied substantially entirely in software installed in at least one existing personal computer 20 equipped with at least one audio transducer.

29. A method according to claim 28 wherein said software is installed on multiple computers located in mutually disparate locations and also comprising providing an output indication of at least one of absence and presence of persons in the vicinities of 25 said multiple computers.

30. A method according to claim 28 and wherein said output indication is a mutually time-coordinated indication of both absence and presence of persons in the vicinities of said multiple computers.

31. A method according to claim 21 and also including anti-hacking warning functionality which is operative to sense the receipt of keystrokes purportedly coming from a computer in respect of which said detection circuitry indicates the absence of a non-stationary object in the vicinity thereof and to provide a hacking warning in 35 response thereto.

32. A method according to claim 27 and including client computer user interface disabling functionality operative in response to indicated absence of a person from the vicinity of a computer for at least a predetermined time.

33. A method according to claim 27 and including client computer user interface enabling functionality operative in response to indicated presence of an authorized person from the vicinity of a computer.

34. A method according to claim 21 and also including guard tour logging functionality which is operative to sense the time relationship of the presence of a person sequentially in the vicinities of multiple computers in a facility.

35. A method according to claim 34 and wherein said guard tour logging functionality includes exception notification functionality operative to provide an indication of departure from a pre-established guard round schedule.

15 36. A method according to claim 21 and also including automatic infrastructure operation/termination functionality which is operative to operate infrastructure facilities in response to output indications of the presence and absence of persons in vicinities of personal computers- 2o 37. A method according to claim 21 and wherein at least one of said at least one audio transducer are selectably positionable with respect to said personal computer.

18.

A method according to claim 21 and wherein said audio energy is in the form of a chirp.

39. A method according to claim 23 and wherein said audio energy is in the form of a chirp and different ones of said plural computers have different characteristic chirps.

30 40- A method according to claim 21 and also including distinguishing between audio energy reflected non-stationary objects located respectively within and outside at least one protected region.

41. A personal computer system operative for detecting the presence of a non-stationary object in the vicinity thereof and comprising: a personal computer; at least one first audio transducer associated with the at least one personal computer and receiving driving inputs therefrom; 16 at least one second audio transducer associated with the at least one personal computer and providing received signal inputs thereto; circuitry, at least associated with the at least one personal computer, for providing said driving inputs to said at least one first audio transducer, thereby 5 causing it to generate audio energy in the vicinity of the at least one personal computer; circuitry, at least associated with the at least one personal computer, for receiving said received signal inputs from said at least one second audio transducer, representing audio signals received from the vicinity of the at least one personal 10 computer, including reflections of audio energy generated by said at least one audio transducer from objects in said vicinity; and circuitry, at least associated with the at least one personal computer for determining whether a non-stationary object has been detected based on an analysis of said received signal outputs and said driving inputs.

42. A system according to claim 41 and wherein said at least one personal computer comprises a single personal computer.

43. A system according to claim 41 and wherein said at least one personal 20 computer comprises plural personal computers.

44. A system according to claim 43 and wherein said plural personal computers have overlapping regions of protection in which a nonstationary object may be detected by said detection circuitry.

45. A system according to claim 44 and wherein said plural personal computers cooperate to detect non-stationary objects.

46. A system according to claim 41 and also comprising presence/absence 30 circuitry receiving an input from said detection circuitry for indicating at least one of the presence and absence of a person in the vicinity of said at least one personal computer.

47. A system according to claim 41 and wherein said presence/absence circuitry 35 provides output indications of both presence and absence of a person in the vicinity of said at least one personal computer.

48. A system according to claim 41 and wherein said system is embodied 17 substantially entirely in software installed in at least one existing personal computer equipped with at least one audio transducer.

49. A system according to claim 48 and wherein said software is installed on 5 multiple computers located in mutually disparate locations and also comprising a monitoring server which correlates outputs of said detection circuitry thereby to produce an output indication of at least one of absence and presence of persons in the vicinities of said multiple computers.

io 50. A system according to claim 48 and wherein said output indication is a mutually time-coordinated indication of both absence and presence of persons in the vicinities of said multiple computers.

51. A system according to claim 41 and also including anti-hacking warning 15 functionality which is operative to sense the receipt of keystrokes purportedly coming from a computer in respect of which said detection circuitry indicates the absence of a non-stationary object in the vicinity thereof and to provide a hacking warning in response thereto.

2o 52. A system according to claim 47 and including a client computer user interface disabling facility operative in response to indicated absence of a person from the vicinity of a computer for at least a predetermined time.

53, A system according to claim 47 and including a client computer user interface 25 enabling facility operative in response to indicated presence of an authorized person from the vicinity of a computer.

54. A system according to claim 41 and also including guard tour logging functionality which is operative to sense the time relationship of the presence of a 30 person sequentially in the vicinities of multiple computers in a facility.

55, A system according to claim 54 and wherein said guard tour logging functionality includes exception notification functionality operative to provide an indication of departure from a pre-established guard round schedule.

56. A system according to claim 41 and also including automatic infrastructure operation/termination functionality which is operative to operate infrastructure facilities in response to output indications of the presence and absence of persons in 18 vicinities of personal computers, 57. A system according to claim 41 and wherein at least one of said at least one first audio transducer and said at least one second audio transducer are selectably 5 positionable with respect to said personal computer.

A system according to claim 41 and wherein said audio energy is in the form of a chirp.

io 59. A system according to claim 43 and wherein said audio energy is in the form of a chirp and different ones of said plural computers have different characteristic chirps.

60. A system according to claim 41 and wherein said detection circuitry is 15 operative to distinguish between audio energy reflected non-stationary objects located respectively within and outside at least one protected region.

61. For use in a method for detecting the presence of a non-stationary object in the vicinity of a personal computer, software installable in the at least one personal 20 computer and having the following functionality when installed; audio energy generating functionality, causing circuitry, at least associated with the at least one personal computer to provide driving inputs to at least one audio transducer, thereby causing it to generate audio energy in the vicinity of the at least one personal computer; 25 reflected audio energy receiving functionality, causing circuitry, at least associated with the at least one personal computer to receive received signal inputs from said at least one audio transducer, representing audio signals received from the vicinity of the at least one personal computer, including reflections of audio energy generated by said at least one audio transducer from objects in said vicinity; and 30 analysis functionality, determining whether a non-stationary object has been detected based on an analysis of said received signal outputs and said driving inputs.

62. Software according to claim 61 and wherein said at least one personal computer comprises a single personal computer.

63. Software according to claim 61 and wherein said at least one personal computer comprises plural personal computers.

64. Software according to claim 63 and wherein said plural personal computers have overlapping regions of protection in which an object may be detected by said detection circuitry.

5 65. Software according to claim 64 and wherein said plural personal computers cooperate to detect non-stationary objects.

66. Software according to claim 61 and also comprising presence/absence functionality including indicating at least one of the presence and absence of a person 10 in the vicinity of said at least one personal computer.

67. Software according to claim 61 and also comprising indicating both presence and absence of a person in the vicinity of said at least one personal computer.

15 68, Software according to claim 61 and wherein said software is installed in at least one existing personal computer equipped with at least one audio transducer.

69, Software according to claim 68 wherein said software is installed on multiple computers located in mutually disparate locations and also comprising providing an 20 output indication of at least one of absence and presence of persons in the vicinities of said multiple computers.

70. Software according to claim 68 and wherein said output indication is a mutually time-coordinated indication of both absence and presence of persons in the 25 vicinities of said multiple computers.

71. Software according to claim 61 and also including anti-hacking warning functionality which is operative to sense the receipt of keystrokes purportedly coming from a computer in respect of which said detection circuitry indicates the absence of a 30 non-stationary object in the vicinity thereof and to provide a hacking warning in response thereto.

71 Software according to claim 67 and including client computer user interface disabling functionality operative in response to indicated absence of a person from the 35 vicinity of a computer for at least a predetermined time.

73. Software according to claim 67 and including client computer user interface enabling functionality operative in response to indicated presence of an authorized person from the vicinity of a computer.

74. Software according to claim 61 and also including guard tour logging functionality which is operative. to sense the time relationship of the presence of a person sequentially in the vicinities of multiple computers in a facility.

75. Software according to claim 74 and wherein said guard tour logging functionality includes exception notification functionality operative to provide an indication of departure from a pre-established guard round schedule.

76. Software according to claim 61 and also including automatic infrastructure operation/termination functionality which is operative to operate infrastructure facilities in response to output indications of the presence and absence of persons in vicinities of personal computers.

77. Software according to claim 61 and wherein at least one of said at least one audio transducer are selectably positionable with respect to said personal computer.

78. Software according to claim 61 and wherein said audio energy is in the form 20 of a chirp.

79, Software according to claim 63 and wherein said audio energy is in the form of a chirp and different ones of said plural computers have different characteristic chirps.

80. Software according to claim 61 and also including functionality distinguishing between audio energy reflected non-stationary objects located respectively within and outside at least one protected region.