Patent Publication Number: US-2005138417-A1

Title: Trusted network access control system and method

Description:
FIELD OF THE INVENTION  
      The present invention relates generally to the field of computer networks and more particularly to a trusted network access control system and method.  
     BACKGROUND OF THE INVENTION  
      As the internet and communication tools have become more common, more employees are working at home or otherwise require access from a remote location to their company&#39;s protected computer network. Virtual Private Network (VPN) servers and other remote access controllers are used to limit access to the company&#39;s protected network to legitimate uses. However, these remote access controllers do not ensure that the remote user and remote systems are complying with the company&#39;s corporate standards and security policies. It is not uncommon for these remote computers to be either personal computers or to have mixed business and personal use. Under these circumstances it is common for these remote computers to have viruses, worms, spyware or other potentially damaging agents. These remote computers can then introduce these harmful agents to the company network.  
      Thus there exists a need for a system and method that allows only trusted remote computers access to protected networks and prevents untrusted remote computers from accessing and introducing harmful agents into the protected network.  
     SUMMARY OF THE INVENTION  
      A trusted network access control system that overcomes these problems includes a remote computer running an advisor. A first trusted network access control device is coupled to the remote computer by a network. A director is coupled to the first trusted network access control device and controls the first trusted network access control device. In one embodiment, a remote access controller is coupled to the first trusted network access control device. A second trusted network access control device is coupled to the remote access controller. In another embodiment, a protected network is coupled to the first trusted network access control device.  
      In one embodiment, a protected network is coupled to the second trusted network access control device. In one aspect of the invention, the director controls the second trusted network access control device.  
      In one embodiment, the advisor sends a trusted state information packet to the director. The director evaluates the trusted state information packet and sends a network access control information packet to the first trusted network access control device.  
      In another embodiment, the first network access control device is a router.  
      In one embodiment, a method of trusted network access control includes the steps of sending a trusted state information packet from a remote computer through a network to a director. The level of access allowed the remote computer is determined at the director using the trusted state information packet. An access control information packet is transmitted from the director to a trusted network access control device. In one embodiment when the remote computer is allowed access by the director, the remote computer communicates with a device on a protected network.  
      In another embodiment, when the remote computer is allowed access by the director, a remote access control information packet is sent from the remote computer to a remote access controller. When the remote computer is allowed access by the remote access controller, a second trusted state information packet is sent to a second director.  
      In one embodiment, an access control information packet is transmitted from the second director to a second trusted network access control device including a remote computer identifier. In one embodiment, a location identifier is transmitted. In another embodiment, a level of trustworthiness is determined.  
      In one embodiment, a method of trusted network access control, includes the steps of requesting access to a protected network by a remote computer. A trustworthiness of the remote computer is determined by a network access controller. A level of access to the protected network by the remote computer is provided. In one embodiment, access to the protected network is denied to the remote computer. In another embodiment, access to a part of the protected network is allowed to the remote computer. In another embodiment, access to all of the protected network by the remote computer is allowed.  
      In one embodiment, a plurality of trust policies are determined. A trust state of the remote computer is evaluated against the plurality of trust policies. In one embodiment, when the trust state fails one of the plurality of trust policies, the level of access is set to no access.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a block diagram of a trusted network access control system in accordance with one embodiment of the invention;  
       FIG. 2  is a block diagram of a trusted network access control system in accordance with one embodiment of the invention;  
       FIG. 3  is a flow chart of the steps used in a method of trusted network access control in accordance with one embodiment of the invention; and  
       FIG. 4  is a flow chart of the steps used in a method of trusted network access control in accordance with one embodiment of the invention.  
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a block diagram of a trusted network access control system  10  in accordance with one embodiment of the invention. The system  10  has a remote computer  12  running an advisor  14 . The remote computer  12  is coupled through a network  16  to a trusted network access control (TNAC) device  18 . The network  16  may be the internet, an intranet, public switched telephone network, other data communication network or a combination of these networks. The trusted network access control device  18  is coupled to a director  20  and to a protected network  22 . The trusted network access control device  18  may be a router, firewall, switch, bridge or other network device that is controllable. The director  20  may be a computer that runs director software. In one embodiment, the director and the trusted network access control device are combined to form a network access controller. Note that while a single remote computer  12  is shown, the system is designed for one or many remote computers connecting to the trusted network.  
      When the remote computer  12  wants to access the protected network  22 , which may be a company&#39;s internal network, the advisor  14  determines a trust state of the remote computer  12 . The computer  12  then sends a trusted state information packet to the director  20 . The director  20  evaluates the trusted state information and determines a level of access. The level of access information is forwarded to trusted network access control device  18 . There are three broad categories for the level of access: 1) no-access; 2) complete access; and 3) limited access. When the level of access is no-access, the trusted network access control device  18  prevents the remote computer  12  from accessing the protected network  22 . The trusted network access control device  18  does this by refusing to accept or forward any data from the remote computer  12  to any device on the protected network  22 . When the level of access is complete access, the remote computer  12  may communicate with any device on the protected network  22 . When the level of access is limited access, the remote computer  12  is only allowed to communicate with selected devices on the protected network  22 . This is accomplished by reviewing the destination address for any data sent from the remote computer  12 .  
      The required trusted state information is determined by the trust policies that are stored in the director  20 . If the advisor  14  attempts to log-in with outdated trust policies it is denied access and the advisor 14  updates its trust policies from the director  20 . Then the remote computer  12  requests access again using the new trust policies to formulate the trusted state information. The trust policies are set by the company or system administrator and may include determining: 1) is anitvirus software installed and running? 2) is file sharing enabled? 3) is the operating system the most recent version including patches? 4) is the personal firewall software running? 5) is any spyware installed or running? 6) is the computer using a wireless network? 7) is the wireless encryption protocol enabled? 8) is the computer connected to a public network? 9) is a password protected screen saver enabled? 10) is the computer being actively used? The director  20  may evaluate the trusted state information and require perfect compliance or it may score the information and compare it to a threshold. The score may determine whether the access is complete or limited. In addition, the remote computer  12  may be any computing platform, such as a PDA, cell phone, personal computer, etc. In one embodiment, the remote computer  12  must send its trust information periodically, for instance every five minutes. If the remote computer does not send its trust state information periodically or the new trust state information fails to establish the proper trust level the connection to the remote computer  12  is terminated.  
      In one embodiment the advisor  14  also includes a unique digital signature, which may be encrypted, of the remote computer  12  that is authenticated by the director  20 . This allows the director  20  to authenticate the remote computer  12  independent of the user of the remote computer  12 .  
       FIG. 2  is a block diagram of a trusted network access control system  30  in accordance with one embodiment of the invention. In this embodiment of the invention the remote computer  32  may be connected to a network  34  and then a router  36 . The router  36  is coupled through a network  38  to a first trusted network access control device  40 . A first director  42  is coupled to the first trusted network access control device  40 . The trusted network access control device  40  is also coupled to a remote access controller  44 . An example of a remote access controller  44  is a Virtual Private Network (VPN) server. The remote access controller  44  is coupled to a second trusted network access control device  46 . A second director  48  is coupled to the second trusted network access control device  46 . A protected network  50  is coupled to the second trusted network access control device  46 . A couple of devices  52 ,  54  may be attached to the network  50 .  
      Note that the remote computer  32  is on a network  34  with a plurality of other computers  56 . When the remote computer  32  requests access from the first trusted network access control device  40 , the first director  42  may be limited in its ability to differentiate between the remote computer  32  and the plurality of other computers  56  on the same network  34 . Once the remote computer  32  is allowed access by the first director  42 , it is required to log onto the remote access controller  44 . The remote access controller  44  authenticates the user and assigns a remote computer identifier. For instance, it may establish a VPN connection and may assign the remote computer  32  a unique VPN endpoint network address or remote computer identifier. The remote computer  32  then requests access from the second director  48 . This allows the second director  48  to uniquely identify the remote computer  32  from the other computers  56  and ensure that none of the other computers  56  are attempting to access the protected network  50  without permission. In one embodiment, the first director  42  and the second director may be one and the same. The trust policies may be the same or different. In some embodiments, the first trusted network access control device  40  may be combined with the remote access controller  44  or the second trusted network access control device  46  may be combined with the remote access controller  44 . In one embodiment both the first and second trusted network access control devices  40 ,  46  and the remote access controller  44  are the same device.  
      The remote computer  32  may be allowed limited access to the protected network  50 . For instance, the remote computer  32  may be allowed to communicate with device- 1   52  but not with device- 2   54 .  
       FIG. 3  is a flow chart of the steps used in a method of trusted network access control in accordance with one embodiment of the invention. The process starts, step  70 , by requesting access to a protected network by a remote computer at step  72 . Next, a trustworthiness of the remote computer is determined by a network access controller at step  74 . At step  76  a level of access to the protected network by the remote computer is allowed which ends the process at step  78 .  
       FIG. 4  is a flow chart of the steps used in a method of trusted network access control in accordance with one embodiment of the invention. The process starts, step  90 , by sending a trusted state information packet from a remote computer through a network to a director  92 . The director determines a level of access allowed by the remote computer using the trusted state information packet at step  94 . At step  96  an access control information packet is transmitted from the director to a trusted network access control device which ends the process at step  98 .  
      Thus there has been described a system and method for trusted network access control which allows only trusted remote computing platforms access to protected networks and prevents untrusted remote computing platforms from accessing and introducing harmful agents into protected networks.  
      The methods described herein can be implemented as computer-readable instructions stored on a computer-readable storage medium that when executed by a computer will perform the methods described herein.  
      While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alterations, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alterations, modifications, and variations in the appended claims.