Patent Publication Number: US-2007118897-A1

Title: System and method for inhibiting access to a computer

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      This invention relates to the field of computer security. More specifically, the present invention comprises a method and system for logging a user off or locking a user account on a computer when a user leaves a work station.  
      2. Description of the Related Art  
      Various devices exist for preventing the unauthorized access of computers. Most of these devices are directed to lockout mechanisms which prevent an unauthorized user from logging onto a computer.  
      For example, U.S. Pat. No. 5,960,084 to Angelo describes a method of enabling power to a computer system based upon the results of a two-piece user verification procedure. If the user does not provide the required “smart card” and password, power to the computer system is disabled.  
      Another example is U.S. Pat. No. 6,338,142 to Alsaadi. Alsaadi&#39;s patent discloses a lockout circuit which generates an interfering signal that disrupts the “power on” signal generated by the computer&#39;s power controller. The lockout circuit generates this interfering signal when triggered by a triggering device such as an Ethernet chip or a switch.  
      Yet another example is provided in U.S. Pat. No. 5,712,973 to Dayan et al. Dayan et al.&#39;s patent discloses a security feature which renders a computer system inoperable when an unauthorized user moves the system out of a containment region. To accomplish this, Dayan et al. uses a radiation source, such as a radio frequency transmitter, to transmit radiation with particular characteristics throughout the containment zone. Logic circuitry is provided as part of the system to disable access when the radiation is no longer detected.  
      Many other devices are also known in the art. Like the aforementioned security systems, however, these devices are directed at preventing an unauthorized user from logging onto the system. None of the prior art devices prevent an unauthorized user from accessing the computer system if an authorized user has already logged onto the computer system and temporarily left the workstation.  
     BRIEF SUMMARY OF THE INVENTION  
      The present invention comprises a computer security system which prevents an unauthorized user from accessing the computer system when an authorized user has already logged onto the computer system and has temporarily left the workstation. The computer security system generally includes a sensor which is configured to detect the presence of a person in the region around a workstation and a processing unit which logs out of the computer when a person is no longer present in the region. A time delay setting may be employed to restrict the log out process to instances where the user is away from the workstation for a specified period of time. An optional calibration tool may be provided to set the sensitivity of the sensor and prevent accidental logging out when the authorized user is still present in the region and the workstation. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       FIG. 1  is a perspective view, showing the present invention.  
       FIG. 2  is a schematic, showing the present invention.  
       FIG. 3  is a diagram, showing the present invention. 
    
    
     REFERENCE NUMERALS IN THE DRAWINGS  
       10  computer security system  
       14  monitor  
       18  cord  
       22  A/D converter  
       26  central processing unit  
       12  computer  
       16  sensor  
       20  sensor signal transmitter  
       24  sensor/CPU interface  
       28  memory  
       30  program  
       34  sensor input  
       38  comparator  
       42  calibration tool  
       46  logoff module  
       32  calibration tool  
       36  signal sampler  
       40  signal criteria  
       44  command  
     DETAILED DESCRIPTION OF THE INVENTION  
      The present invention, computer security system  10 , is illustrated in  FIG. 1 . Computer security system  10  is employed to prevent an unauthorized user from accessing the computer system if an authorized user has already logged onto the computer system and temporarily left the workstation. Computer security system  10  may be employed in any setting where one wishes to limit access.  
      As shown in  FIG. 1 , computer security system  10  includes sensor  16  which is plugged into computer  12  with cord  18 . Cord  18  serves as a conduit for power and data transfer. Cord  18  may be a universal Serial Bus (“USB”) adapted cord or any other cord which will support data transfer between sensor  16  and computer  12 . In addition, a separate power cord may also be provided to sensor  16  with its own transformer and wall plug. Computer  12  is also provided with monitor  14 . Although a desktop-type computer is shown in  FIG. 1 , the invention may also be employed on a laptop computer. If a laptop is used, sensor  16  may either be external to the laptop or internally integrated.  
      Sensor  16  may be any type of sensing means that is configured to detect whether a person is present in the region around the user&#39;s workstation. As an example, sensor  16  may be a motion detector type sensor. Common motion detectors utilize microwave or infrared transmitter/receiver circuits. These sensors may be used to detect the movement of objects around the workstation. Sensor  16  may also be a thermal sensor which detects relative temperature of objects around the workstation. For example, sensor  16  may utilize “forward looking infrared” technology. In addition, sensor  16  may also be a camera or electro-optical sensor which captures a pictorial layout of the workstation and transmits the pictorial layout as sensory data (such as in an array of pixels). Pictorial type motion detectors compare frames of pixels with a reference frame. A processor then computes the degree of divergence between the reference frame and the “live action” frames. A greater description of these sensors is omitted here since these types of sensors are well known.  
      A schematic of an electronic circuit incorporating the present invention is provided in  FIG. 2 . Sensor signal transmitter  20  transmits sensory data from sensor  16  to the electronic circuit. The type of sensory data transmitted by sensor signal transmitter  20  depends on the type of sensor that is used. If a motion detector type sensor is used, sensor signal transmitter may send a simple signal indicating that movement has been detected in the region around the workstation. If a thermal sensor is utilized, thermal imagery data may be transmitted by sensor signal transmitter  20  or a simple “trigger level exceeded” signal.  
      Sensor signal transmitter  20  may transmit the sensory data to A/D converter  22  to convert the signal representing the sensory data from analog to digital format. Obviously, A/D converter  22  is not necessary if the sensor normally transmits in digital format. A/D converter  22  may be integrated with sensor  16  so that they are packaged together in one unit.  
      A/D converter  22  transmits the sensory data to sensor CPU interface  24 . The sensory data may be any type of data that may be used to confirm the presence or absence of the user. For example, the sensory data may be a continuous stream of data from the sensor or a “trigger level exceeded” signal. In the preferred embodiment sensor/CPU interface  24  is a USB port, but other computer ports may similarly be used. Central processing unit  26  interfaces with sensor  16  through sensor/CPU interface  24 . Central processing unit  26  is a processing means which is configured to process the sensory data and determine whether a person is present in the region around the workstation. Central processing unit  26  may be the central processing unit associated with the computer or it may be a standalone or computer-implanted processing device.  
      Central processing unit  26  is associated with memory  28 . Memory  28  may be any type of memory unit that may be read by central processing unit  26  including RAM, ROM, computer readable disk, and other external storage devices. Memory  28  stores program  30  and calibration tool  32 . Memory  28  may also service central processing unit  26 &#39;s short-term memory needs. Program  30  is a computer program which includes a program module for directing central processing unit  26  in making a determination of whether a person is present in the region around the workstation. Calibration tool  32  includes a calibration module for calibrating program  30  with sensor  16  and the default state of the region around the workstation as will be described subsequently. It also may include a module for setting a sensitivity threshold for the sensor.  
      An information flow diagram illustrating the relationship between the various components of the present invention is provided in  FIG. 3 . Sensor input  34  represents the flow of sensory data to central processing unit  26 . Sensory data is transmitted from sensor input  34  to signal sampler  36 . Signal sampler  36  is a section of the program module which samples the sensory data for specific characteristics. Comparator  38  compares the sampled sensory data signal with stored sensory data describing a default state of the region around the workstation.  
      Calibration tool  42  represents the calibration module that may be used to calibrate the sensor and program module with a “default state” of the region around the workstation. “Default state” may describe the workstation when the authorized user of the computer is present or absent. If a motion detector type sensor is used, the default state is preferably the state of the region around the workstation when the authorized user is absent. Accordingly, a motion detector type sensor should be calibrated to a state where objects are not moving in the region around the workstation. Calibration tool  42  may be unnecessary for security systems with motion detector type sensors if the sensor sends a defined signal only when motion is detected in the area. Calibration tool  42  may still be useful in this situation, however, because the sensor/program module may be set to various “sensitivities.” For example, calibration tool  42  may be used to associate repetitive motion with the presence of a person in the workstation. On the other side, one movement that is detected in the span of  30  seconds may not be associated with the presence of a person.  
      For thermal sensors, the “default state” may be defined as either the presence or lack of a human heat signature. If the default state is defined by the absence of a person in the region around the workstation, calibration tool  42  may be used to take a thermal “snapshot” of the region around the workstation when a person is not present. If the default state is defined by the presence of a person in the region around the workstation, calibration tool  42  may be used to take a thermal snapshot when a person is present. As with motion detector type sensors, calibration tool  42  may also be used to set a sensitivity threshold for divergence from the “default state.” This feature is especially useful for thermal sensors as the workstation may see different temperature conditions throughout the year.  
      “Sensitivity threshold” corresponds to a measurable value for which divergence must equate or exceed before a sampled signal “meets the criteria” required by comparator  42 . This divergence value may be set by the user when the user installs the security system at the workstation. It may need to be recalibrated over time—particularly if the environment around the workstation changes.  
      The value of divergence assigned by the user and required by comparator  42  will vary. It is dependant on the type of sensor that is used as well as the habits of the user and the characteristics of the region around the user&#39;s workstation. As mentioned with respect to motion detector type sensors, sensitivity threshold may define how many “motion” signals must be registered in a defined period of time. For thermal sensors, sensitivity threshold may define a required thermal contrast which must be observed or temperature range or “heat signature” that must be present.  
      As mentioned previously, camera type sensors may also be used to determine whether a person is in the region around a workstation. For example, a camera may collect digital imagery continuously or periodically of the area. Calibration tool  42  may be used to define the default state for either the case where the authorized user is present or absent. Using calibration tool  42 , a pictorial snapshot may be taken of the area in the default state and stored for comparison purposes. Similar to thermal sensors, the camera type sensor may also be calibrated for the appropriate sensitivity threshold. Sensitivity threshold in the camera type sensor context may describe specific contrasts which must be achieved in terms of pixel array to meet the signal criteria required by comparator  38 . Alternatively, sensitivity threshold may define how many pixels must be different in a live action frame from a reference frame.  
      Calibration and sensitivity threshold information is stored as signal criteria  40 . Signal criteria  40  includes both sensory data regarding the default state and the sensitivity threshold parameters described previously. Comparator  38  compares sensory data signals received from signal sampler  36  with signal criteria  40  to determine whether the sensory data signal(s) meet signal criteria  40 .  
      Although it has been mentioned that the default state may include both the cases where the authorized user is present and the case where the authorized user is absent, for purposes of illustration it will be assumed that the default state is that the user is absent. Accordingly, if a sensory data signal indicating that a person is present is sent to comparator  38 , comparator  38  compares the signal with signal criteria  40  and will determine that signal criteria  40  is met. In the motion detector context, comparator  38  may receive sensory data signals indicating 5 registered movements over the past 30 seconds. In this case, comparator  38  may determine that the signals meet signal criteria  40 , and signal comparator  38  continues to receive sensory data from signal sampler  30 . In the thermal sensor context, comparator  38  may receive sensory data signals indicating that a certain thermal contrast was observed, comparator  38  may determine that the thermal contrast meets signal criteria  40  (if the thermal contrast corresponds to the thermal context expected with the presence of a human heat signature), and comparator  38  continues to receive sensory data from signal sampler  30 .  
      Optionally, if a “YES” determination is made (if the signal meets the criteria), central processing unit  26  may also send wakeup signal  46 . Wakeup signal  46  corresponds to a command signal which prevents a program from going into a rest state. For example, wakeup signal  46  may be a command signal that prevents the computers operating system from launching a “screen saver.” Wakeup signal  46  may similarly be used in other situations where the user does not want the computer to register an “idle” state. Many programs and Internet resources utilize these shut-down-at-idle mechanisms to conserve bandwidth and computer resources when they are “apparently” not being utilized. The user may in fact be using the program but may not have “shown” the program that it was still in use.  
      If a “NO” determination is made (signal does not meet criteria), central processing unit  26  sends command  44 . Command  44  may be many different types of command signals. The exact command signal that is sent will depend on the type of operating system used by the authorized user and whether special authentication programs are used on the program. The command signal is generally configured, however, to block access to the computer until the authorized user completes an authentication process with respect to the computer. For MICROSOFT WINDOWS type operating system on a MICROSOFT type server, the command signal may be the object code equivalent of pressing the “Ctrl”, “Alt” and “Delete” keys simultaneously.  
      Command  44  generally triggers logoff module  48 . Logoff module  48  may be any mechanism configured to block access until the user completes an authentication process. An actual “logging out” of the user&#39;s account may not be required in all cases. A specific module may be provided to prevent access and require authentication. This module may be provided in combination with program  30 . Program  30  may be configured to operate in connection with various operating systems, servers, and authentication programs used by the user.  
      The invention may be better understood by the following example. In this example, the user has installed a microwave transmitter/receiver type motion detector sensor to the user&#39;s workstation computer. The motion detector sensor exchanges sensory data with the computer through a USB cord attached to one of the computer&#39;s USB ports. The user has installed program  30  with calibration tool  32  on the computers hard drive.  
      The computer&#39;s central processing unit  26  searches the computer&#39;s communication ports and recognizes that a microwave transmitter/receiver type motion detector sensor is plugged into the computer&#39;s USB port as part of the logging in protocols of program  30 . The user may then open calibration tool  32  and run the calibration module. Calibration tool  32  translates the sensory data received from sensor  16  into descriptive “motion information” such as the number of movements detected by the sensor over time. The user may run the calibration module in background mode while working on other matters to gather information regarding the level of “motion activity” which is normally present in region around the workstation. If the user runs the module for an hour, calibration tool  32  may provide the following descriptive motion information to the user: 
          Run time: 60 minutes, 0 seconds     Total movements detected: 523     Longest idle: 36 seconds     Sensitivity setting: 5        

      This information means that over the course of the hour long calibration run, 523 total movements were detected by the sensor with a longest period of time between detected movements of 36 seconds. The sensitivity setting of the sensor was set to 5 (a medium sensitivity setting in a sensitivity range of 1 to 10). For microwave transmitter/receiver type motion detectors, the sensitivity setting is directly proportional to the level of “movement” required for the sensor to send a “movement detected signal.” If the user had used a higher sensitivity setting (such as 8) in the previous calibration run, the longest idle period may have been shorter than 36 seconds since more subtle movements were not detected with a sensitivity setting of 5. Accordingly, the user can select the appropriate sensitivity setting to minimize the “longest idle” time that is likely to be observed when the user remains in front of the workstation. This objective generally must be balanced against the objective of eliminating false positives (instances where the sensor detects movement when the user is not in front of the workstation).  
      Using calibration tool  32 , the user may also set the time period for sending a log off command. If the user selects the sensitivity setting of 5, then the user should set a time delay period greater than 36 seconds so that the computer is less likely to log out when the user is still in front of the workstation. Alternatively, calibration tool  32  may include an automatic calibration module. The automatic calibration module may include an algorithm for balancing the sensitivity setting and the time delay period automatically.  
      Once the sensor and program are calibrated to the user&#39;s workstation, program  30  runs in background mode to detect instances when the user leaves the region around the workstation. If the user selects a time delay period of 1 minute, comparator  38  observes the sensory data until a time lapse greater than 1 minute occurs between “movement” signals. For example, after every “movement” is detected, a time delay counter counts 60 seconds. Each “movement” signal restarts the counter. If the counter reaches 60 seconds, central processing unit  26  is directed to send command  44  to log the user out.  
      The preceding description contains significant detail regarding the novel aspects of the present invention. It should not be construed, however, as limiting the scope of the invention but rather as providing illustrations of the preferred embodiments of the invention. As an example, the aforementioned security system may block access in many ways other than logging out of the user&#39;s account, including limiting the display of screens, specific data or programs, as well as preventing the copying and writing of files. In addition, access may also be blocked without actually closing programs. The specific implementation of the security may vary based on the user&#39;s needs. Also, other sensors which relay sensory information may be used than the examples provided in the preceding description. For example, pressure sensitive pads may be used on or under the user&#39;s chair to detect the presence of the user. Such variations would not alter the function of the invention. Thus, the scope of the invention should be fixed by the following claims, rather than by the examples given.