Patent Publication Number: US-8544062-B2

Title: Method and system for improving computer network security

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is filed under 37 U.S.C. 371 based on International Patent Number PCT/IL2004/001073 which claims the benefit of the filing date of United States Provisional Application for Patent entitled “METHOD AND SYSTEM FOR IMPROVING COMPUTER NETWORK SECURITY” and which was filed on Dec. 3, 2003 and assigned Ser. No. 60/526,446, the content of which is incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISK APPENDIX 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to the field of private network security and, more particularly, to protecting private networks from leakage or extraction of information or insertion of unapproved material when the clients are connected to the private network or not connected (i.e., working online or offline). 
     Commercial corporations, enterprises, organizations, such as government, health, military, financial, etc., face several computer security concerns. One of these concerns is the leakage of information from their internal computer network to the outside world. The threat of information leakage may come from outsiders as well as from inside the organization by disloyal or careless employees. 
     Internal employees may use their permission to gain access to the enterprise&#39;s information, download the information to their client computer and then transfer the information to an external device. The external device may be a removable storage device (e.g. flash memory, such as but not limited to, DiscOnKey or a removable hard disk drive), a removable storage media (e.g., floppy disk or writable CD ROM), a PDA, a cellular phone, WiFi dongle, MP3 player, Bluetooth dongle, printer, digital camera, tokens, etc. DiskOnKey is a registered trademark of M-Systems. A PDA is an acronym for Personal Digital Assistant, a handheld device that may have computing, telephone/fax, Internet and networking features. Communication with such external devices may be done over a variety of data communication physical ports such as USB, FireWire, PCMCIA bus, SCSI bus, iSCSI, Cellular, Infiniband, Serial, Parallel, LAN port, Fiber Channel, Infrared, wireless communication such as but not limited WiFi, Bluetooth, etc. 
     Another device that may be used for transferring information out of an organization is the employee&#39;s portable computer (e.g. a laptop computer, a cellular device). Today, in many organizations, a peer may have a laptop computer instead of, or in addition to his desktop computer. An employee can easily copy valuable information onto the laptop and then carry it out. Subsequently, when the laptop is not connected to the private network, the valuable information can be copied, undetectably, to another storage device. 
     One common approach to deal with this type of security threat is by preventing access to valuable information or preventing the transfer of valuable information to external devices. Preventing the access to the information may be done physically or by software means. In addition, a user&#39;s ability to access an external storage device for the purpose of transferring information can also be prevented using physical or software techniques. However such common methods have a significant adverse effect, they can easily reduce the productivity of the users within an organization because the users may need to access the valuable information or external storage devices during day-to-day operations. 
     Therefore, there is a need in the art for new method that may offer a wider variety of options for controlling the transfer of information and the access to external devices. A technique for addressing this need in the art would preferably (a) permit a user to transfer certain files but prevent files containing more sensitive or valuable information from being transferred or (b) may allow access to some of the functions of an external device while preventing access to other features. For example, the technique may allow a user to synchronize his or her personal diary in the user&#39;s personal computer with the diary in his or her PDA yet prevent other files from being transferred to the PDA. 
     Furthermore, there is a need in the art for a method that may verify the environment to which a portable device is connected and restrict information access or information transfer capabilities based on the environment. For instance, once a device is interconnected to an environment, the restriction options associated with this environment can be checked to determine the actions and access privileges allowed in this location and thus, a decision regarding information access and transfer can be determined. This decision may be based, at least in part, on a security policy that is loaded into the portable device. In addition, there is a need in the art for a method that can analyze nesting of a communication protocol within another communication protocol. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention meet the above-described needs in the art by providing a method for selectively preventing access to certain devices according to a security policy that is employed or active. In general, exemplary embodiments of the present invention can operate to analyze the data transportation to or from a physical communication port according to the relevant layers that are used in the communication protocol. Based on the employed security policy and the type of the communication that has been analyzed, a decision is made as to whether to allow the transportation of the data, block the transportation, modify the transportation, inform the user and/or the administrator about the transportation attempt, etc. The security policy may be set by the administrator of the private network according to the user rights and position in the organization. 
     An exemplary embodiment of the present invention may include a Security Manager Module and a plurality of client agents. The Security Manager Module (SMM) can reside on a security server in a central location in the private network and can manage or enforce the security policy. The SMM is operated by a system administrator. The client agent, which may be a software module and/or a hardware device, is installed in each one of the computers that can be connected to the private network. The existence of the client agent can be a mandatory condition for enabling the connection to the private network. In such an embodiment, the private network may not respond to a computer that does not have a client agent. 
     The client agent operates to sniff the data transportation to or from one or more of the physical communication ports or buses, analyzes the data transportation according to the communication protocol and in response to the analysis, determines how to proceed with the data transfer. The policy that is associated with a certain client agent may configure the client agent to block the transportation of certain types of files, such as, but not limited to, software code, source code, drawings, etc. In addition or alternatively, the policy may allow certain applications to be executed while blocking the execution of other applications. Moreover, the client agent may be configured to send an indication to the SMM and can be configured to send messages to the user as well. The policy that is associated with each one of the client agents may be updated from time to time by the administrator via the SMM. 
     For a communication that operates according to the Seven Layer Model, exemplary embodiments of the present invention may analyze one or more layers from the existing layers in order to reach a decision regarding the handling of the communication. Moreover in cases in which the communication is using a nesting of one protocol under another protocol, exemplary embodiments of the present invention may analyze the one or more protocols and may reach a decision on the nested protocol. For example, if a WiFi Dongle is connected to a USB port, both protocols may be analyzed. A decision whether to allow the communication or not may depend, for example, on the SSID (Service Set Identifier—secret token to identify a Wi-Fi) property of the WiFi connection. The SSID property defines the name of the wireless network. 
     Moreover exemplary embodiments of the present invention may verify whether an external device that has been connected to a physical communication port behaves as it is expected to behave or if the device is emulating or impersonating another device. For example, a portable memory that is connected over a USB port may be built to emulate a digital camera upon establishing a connection. Later on, the user may attempt to load files into the portable memory. Exemplary embodiments of the present invention can operate to detect such an activity and then block the communication. Thus, the portable memory can be used as a digital camera for loading information into a computer but any attempt to transfer files to the portable memory will be thwarted. 
     Other objects, features, and advantages of the present invention will become apparent upon reading the following detailed description of the embodiments with the accompanying drawings and appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  illustrates a block diagram with relevant elements of a computer system that uses an exemplary embodiment of the present invention: 
         FIG. 2  is a block diagram with relevant elements of a software system that is used in a client computer according to an exemplary embodiment of the present invention; 
         FIG. 3  is a block diagram illustrating components of the client security agent according to an exemplary embodiment of the present invention; 
         FIG. 4  illustrates a flowchart with relevant steps of an exemplary method for managing input portion of data transportation via the security agent. 
         FIG. 5  illustrates a flowchart with relevant steps of an exemplary method for determining how to proceed with a session of data transportation. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Turning now to the figures in which like numerals represent like elements throughout the several views, exemplary embodiments of the present invention are described. For convenience, only some elements of the same group may be labeled with numerals. The purpose of the drawings is to describe exemplary embodiments of the present invention and not for production or limitation. Therefore, features shown in the figures are chosen for convenience and clarity of presentation only. 
       FIG. 1  is a block diagram with relevant elements of a computer system  100  that uses an exemplary embodiment of the present invention for protecting the computer system from their own clients. The computer system  100  may comprise a plurality of client computers  110   a - c , a private network  120 , a plurality of communication channels  115   a - c  between the private network  120  and the plurality of client computers  110   a - c , and security server  130 . Three instances of client computers  110   a - c  and communication channels  115   a - c  are shown in  FIG. 1  by way of example only, and it will be appreciated that any number other than three may also be used with the present invention. The private network  120  may be an Intranet, cellular network, a LAN, a VPN (Virtual Private Network) or any other type of communication network. 
     Each of the client computers  110   a - c  may be a personal computer, a workstation, a desktop computer, mainframe computer, blade server (e.g. CITRIX), dumb terminal, etc. or any other type of computing device that can be connected over private network  120 . Each of the client computers  110   a - c  may also be a portable device, such as but not limited to a laptop computer, notebook computer, a smart phone, a personal digital assistant (PDA), or any other type of mobile device. The client computer  110   a - c  may be connected to various networks from time to time at home, at work, and at other locations. Communication channels  115   a - c  may be permanent connections, temporary connections, and wire or wireless connections. A wireless connection can be an RF connection based on a protocol such as, but not limited to, Bluetooth or WiFi. The wireless connection may also be an Infra Red (IR) connection. More information about the client computers  110   a - c  is disclosed below in conjunction with  FIGS. 2 and 3 . 
     The security server  130  may be an element of network  120 . The security server  130  may be responsible for managing the security policies that are used over the private network  120 . A plurality of policies may be used by each client computer  110   a - c . The security policies may be based on the client&#39;s degree of security, the environment that the client is working in, the type of the devices that are connected to the client computer, etc. The security policies can be updated from time to time and then be loaded or reloaded into the clients. 
     The security server  130  can operate to ensure that all client computers comply with specified security policies. For example, if a trigger event occurs and a copy of a corporate security policy is not available on a client computer  110   a - c , the client computer  110   a - c  may initiate a connection to the security server  130 . In response to such initiation, the appropriate policies may be downloaded to the client computer  110   a - c . The security server  130  may periodically update the security policies that are installed in each one of the client computers  110   a - c . A security agent may be installed within the client computer  110   a - c  and, among other things, operates to enforce the security policy by monitoring events in accordance with the security policy. 
     The security server  130  can be constructed in a variety of manners and in one embodiment may comprise the following relevant modules: client&#39;s communication module  132 , event logger module  134 , policies database  135 , client database  136 , Man Machine Interface (MMI) module  139  and a manager module  138 . Client communication module  132  is typically used to communicate with the plurality of client computers  110   a - c  over private network  120  while the client computers  110   a - c  are connected to the private network  120 . The communication between the client computers  110   a - c  and the security server  130  can be encrypted to create a secure connection between the client computers  110   a - c  and the security server  130 , over which data can be sent securely. 
     The communication from the security server  130  to the client computer  110  may include: the provision of updated security policies and/or periodically checking whether the installed security agent and the installed security policies have been contaminated or have been tampered with by any hostile code. If a particular client computer does not have a required client security agent or security policy installed, or the security agent was infected, the security server  130  can prevent further access to the corporate network until such client computer has installed and activated the required security agent or security policy. 
     The communication from the client computer  110  to the security server  130  may include: a real-time indication that is used to inform the security server  130  when the client computer  110  is connected to the private network  120 , reports on events according to the security policy, reports on trials to affect the security agent or the stored security policy, etc. The report may include information on any connection of the client computer  110  to an external device, information on the data transfer, the timing of the event, the location, the device to which the data transfer was done, shadowing of the information that was transferred while the client computer  110   a - c  was not connected or connected to network  120 , etc. 
     The event logger  134  may be a storage device that can be used to store the reports that have been sent from the users within a certain period and/or any policy violation event. The reports may be retrieved and processed manually by an administrator of the private network  120  or automatically by the manager module  138 , which may run several statistical algorithms in order to monitor the security of the network. The process may uncover a careless user that may have connected or attempted to connect certain devices to the client computer  110 , may identify attempted access to certain communication ports/buses, and may uncover certain actions with the combination of the location and/or device that infringes the security policy. The report may also identify a negative trend, for example, that in more than one client computer the security agent has been tampered, etc. When a portable client is not connected to the network  120 , the events may be kept by the client agent and be sent to the security server  130  when the client is reconnected to the private network  120 . 
     Policy database  135  is a database that includes a plurality of policies, including security policies that may be used by the organization that owns the private networks  120 . A security policy may include a set of rules that are used to determine whether a given client computer can be permitted to gain access to a specific device. The security policy may depend on various factors. Such factors can include the location of the client, the external devices, the type of applications, etc. For instance, a certain client computer may have different security policies that are activated based on the location at which the client computer is being operated. In addition, different security policies may be allocated to different users; group of users; working hours, etc. 
     Client database  136  is a database that may include information regarding the various client computers  110   a - c  that may be connected over private network  120 . This information may include items such as but not limited to: client level of security, the type of equipment that the client possess, the external devices to which the client computer is allowed to be connected, information about the different environments in which the client computer may work, etc. 
     Manager module (MM)  138  manages the operation of the security server  130 . It may initiate tasks to check the situation of the security agent and the security policies, which are installed in the client computers. MM  138  may create and send the appropriate policies to each one of the client computers. Based on the information that is stored in the policy database  135  and the client database  136 , MM  138  may create one or more policies for a particular client. For example, a client that has a portable computer may need three policies. One policy may be used while the particular client computer is connected to the private network  120 . Another policy may be used when the client computer is operating in a known environment, such as but not limited to his home. The last policy may be used when the client computer is operating in an unknown environment or location. The MM  138  may run Artificial Intelligence algorithms over the information that is stored in the event logger  134  and may send indications and conclusions to the administrator of the network. The MM  138  may receive decisions regarding certain activities of a client computer and affect his connection to the private network  120  based on such decisions. 
     The MMI module  139  may be a graphical user interface (GUI) that may be used by the administrator of the system to communicate with the security server  130 . The MMI may allow simple access to change policies, retrieve and check reports, update the client database  136 , etc. 
       FIG. 2  is a block diagram with the relevant elements of a client system  200  that may be used in an exemplary client computer  110   a - c  ( FIG. 1 ). The client system  200  may comprise one or more application programs  210   a - c , one or more device drivers  220   a - c , a security agent module  230 , one or more physical communication port or bus drivers (stack)  240   a - c , a core kernel module  260  and one or more physical communication ports or buses  250   a - c . Generally, the data transportation between a client computer and a device flows from/to an application  210   a - c  to/from a physical communication port  250   a - c  via the appropriate device driver  220   a - c , security agent  230  and the appropriate port driver  240   a - c . The example illustrated in  FIG. 2  shows the use of three application programs  210   a - c , device drivers  220   a - c , port drivers  240   a - c  and physical communication ports  250   a - c ; however, it will be appreciated that any number other than three may be used with the present invention. The client system  200 , or aspects of the client system  200 , may be stored in a fixed storage medium (e.g. a disc, flash memory, a read-only memory (ROM) etc.). During the operation of the client computer, one or more of the software modules may be retrieved from the fixed storage medium and may be loaded into a temporary memory such as a random-access memory (RAM). 
     The core kernel  260 , the device drivers  220   a - c  and the port/buses drivers  240   a - c  may jointly be referred to as the operating system (OS) of the client computer  110   a - c  ( FIG. 1 ). The OS may manage low-level aspects of computer operation, including managing execution of processes, memory allocation, file input and output (I/O) and device I/O. Exemplary OS utilized may be windows NT or XP, Unix, MAC OS, MVS; LINUX, SYMBIAN, PALOS, etc. One or more application programs  210   a - c  may be transferred from a fixed storage medium into the RAM for execution by the client system  200 . The application program  210   a - c  may be a program such as, but not limited to, (a) synchronization applications for a PDA, (b) Java applications for synchronization with external Java devices, such as but not limited to cellular telephones, backup storage applications and (c) communication applications such as but not limited to application that utilize Bluetooth or WiFi protocols, Internet browser, etc. 
     When the core kernel  260  and/or one or more application programs  210   a - c  may want to communicate with an external device the appropriate device drive  220   a - c  may be invoked. The device driver  220   a - c  is used as an intermediary between the core kernel  260  and/or one or more application programs  210   a - c  and the external device itself. Exemplary external devices can include: a removable storage device, a printer, a PDA, a WiFi dongle, etc. Usually a device driver  220   a - c  is supplied by the vendor of the device itself. In addition to the device driver  220   a - c  a port driver  240   a - c  may also be invoked. The port driver/bus driver  240   a - c  is used to organize the communication according to the protocol that is used over the physical communication port  250   a - c . For example, if communication port  250  is a USB port than a USB driver (USB stack) is needed. The above-described computer software is for illustrating the basic desktop and server computer components that may be employed by a client computer  110   a - c  ( FIG. 1 ). In addition to those elements a security agent  230  is added by an exemplary embodiment of the present invention. 
     The security agent  230  may be installed in the standard storage of the client system  200  and it may be invoked during the power on cycle of the client computer  110   a - c  and remain active for the entire operation of the system. In other embodiments of the present invention, the security agent  230  may be burned onto a physical memory, such as the ROM, PROM, BIOS, etc. The security agent  230  may be installed as a section of the OS and can be handled by an administrator having the appropriate permissions. The security agent  230  may be installed in between the core kernel  260  and the one or more communication port/bus drivers  240   a - c.    
     The security agent  230  may emulate a kernel device driver and will receive the communication between the device driver  220   a - c  and the core kernel  260 . During the installation and/or periodically, from time to time, the security agent  230  may register in the appropriate location in the core kernel as the first device driver for receiving the communication from/to the different physical communication port/bus drivers. For example, if the OS is a Microsoft product, than the security agent  230  may register in the Registry as the first device driver to get the communication. The registration may be done in a class level or in a device level. Exemplary classes may be USB, CD-ROM drivers, Disk Controller, etc. In some operating systems, the device driver may be constructed from a stack of two or more sub-device-drivers. In such architecture, the security agent  230  may collect information from at least one of the two or more sub-device-drivers. For example, in the scenario of using a USB flash storage device, such as but not limited to, DiskOnKey (DiskOnKey is a trademark of M Systems) in the Windows (Windows is a trademark of Microsoft) environment, the stack of the relevant sub-device-drivers can include: VolSnap.sys; Disk.sys; UsbStor.sys; and Usbhub.sys. and the security agent may collect information from any of the four sub-device-drivers. 
     In an embodiment of the present invention the security agent  230  may emulate a filter procedure but, instead of providing the functionality of a common storage filter driver, the security agent performs security checking. A filter may perform device-specific functionality that is not provided by a class device driver. The security agent  230  may emulate more than one type of filter driver. The number of types of filters that may be emulated by the security agent  230  can be configured according to the number of physical communication ports and devices that their transportation may be checked by the security agent  230 . 
     Security agent  230  may be activated when a physical communication port is requested. The security agent  230  may pull the transportation to and from the physical communication port, processes the information and may reach a decision regarding the legality of the requested connection and/or data transfer. Security agent  230  may act as a proxy for both sides. The security agent  230  may be transparent to the user; it may not have any icon or indication to indicate it&#39;s existence to the user. More information about the operation of security agent  230  is disclosed below in conjunction with the description of  FIGS. 3 ,  4  &amp;  5 . 
     Another exemplary embodiment of the present invention (not shown in the drawings) may be used by a private user, who is not connected to a private network. The user may wish to protect the information that is stored in his computer from being copied by others. In such an embodiment, the client system may comprise some additional modules, such as the modules disclosed above in conjunction with the description of the security server  130  ( FIG. 1 ). The additional modules may be a limited policies database  135  ( FIG. 1 ), an event logger  134 , a manager  138  and an MMI module  139 . 
       FIG. 3  is a block diagram with the relevant elements of a software program  300  that may be used by an exemplary security agent  230  ( FIG. 2 ). The software program  300  may comprise a transportation manager (TM)  310 , a buffer controller (BC)  312 , an output controller (OC)  316 , an environment detector (ED)  330 , a self checker  333 , a History checker  336 , a bank of security policies (BOSP)  340 , a bank of protocols (BOP)  342 , a manager and decision maker (MDM)  320 , and one or more transportation processed context (TPC)  350   a - c . Three examples of transportation processed contexts (TPC)  350   a - c  are shown in  FIG. 3  by way of example, and any number other than three may be used with the present invention. Each one of TPC  350   a - c  may comprise a parser  352 , a re-assembler  354  and an analyzer  356 . 
     The data transportation to/from a physical communication port  250   a - c  ( FIG. 2 ) may be transferred via TM  310 , BC  312  and OC  316 . TM  310  may be a software module that manages the transportation via the security agent  230 . The TM  310  may manage a table with the relevant parameters that may be needed to maintain the communication sessions that are currently transferred via the security agent. Exemplary parameters may be the source and the destination address of the data flow. In another example a packet counter that counts each time a data portion is transferred to or from a communication port  250   a - c  ( FIG. 2 ) is used in order to limit the amount of data portions (the size of the file) that are routed to the TM  310 . The data portion may be a packet for a USB communication port or a SCSI block for a SCSI bus. It should be noted that the terms “packet”, “data portion”, “data-gram” and “SCSI block” are used interchangeably herein. Henceforth, the description of the present invention may use the term ‘packet’ as a representative term for any of the above group. From the TM  310 , the packet may be transferred, as is, to BC  312 , which stores the packet in an appropriate location in a buffer according to the source and the destination of the communication. Following this, an indication may be sent to the MDM  320  informing the MDM  320  regarding the new packet. The TM  310  may manage transportation through one or more physical communication ports simultaneously. More information on the operation of TM  310  is disclosed below in conjunction with the discussion of  FIG. 4 . 
     The BC  312 , which can be implemented in a software module, controls a buffer (not shown in the drawings) in which the data transportation, which is currently handled by the security agent  230  ( FIG. 2 ), may be stored. The buffer may be organized in sections; each section may be dedicated to a certain data transfer session. The data from the buffer may be retrieved and processed by an appropriate TPC  350   a - c . The MDM  320 , based on the result of the process that was done by the appropriate one or more TPC  350   a - c , may instruct the BC  312  whether to transfer the data to the output controller  316  to be sent to one or more appropriate destinations or to delete the data that belongs to this session. More information on the operation of the BC  312  is disclosed below in conjunction with the discussion of  FIGS. 4 &amp; 5 . 
     The OC  316  may maintain the connection of the one or more data transfer sessions that are currently transferred via the security agent  230  ( FIG. 2 ). Based on instructions that may be received from the MDM  320 , the OC  316  may block the transportation to/from the appropriate communication port  250   a - c ; or may send the packets to its original destination in a way that the operation of security agent  230  is transparent; or in parallel to being sent to its destination the packets may be sent to a shadowing device (not shown in the drawing) for storage. In order to maintain the flow of operation of the client computer  110   a - c , when needed, the OC  316  may block the transportation of the data while maintaining the connection. An indication may be sent to the user, informing the user that there is a problem in the data communication and the application may continue operation and then terminate in a normal manner. More information on the operation of the OC  316  is disclosed below in conjunction with the discussion of  FIG. 5 . 
     The ED  330  may detect the environment to which the client computer  110   a - c  ( FIG. 1 ) is currently connected. A client may have a portable device, such as but not limited to, a laptop, which may be carried out of the organization&#39;s premises and may be operated in an environment other than the private network  120  ( FIG. 1 ). Thus, the user may operate the portable device within the user&#39;s home where the computer may be connected to his or her Internet service provider, printer, CDROM writer etc. Another exemplary location may be a public place such as a coffee shop, hotel, airport, in which the client may be connected to the Internet via a wireless connection using a WiFi dongle or a Bluetooth dongle. In each environment, it may be necessary to apply a different security policy. 
     Identification of the environment may be based on several criteria. For example, the ED  330  may have one or more environment profiles. From time to time, the profiles may be loaded by the security server  130 . Each user may have its own environment profiles according to the environment in which the user has a tendency to work. Each environment profile may include several parameters that describe or affect various aspects of the environment in which the client computer currently operates. For example, an environment profile may have a list of external devices to which the client may be connected when operating in a particular environment. These external devices may include, but are not limited to, printers, external storage devices, etc. An environment profile may also have information on network elements that may be connected to the client computer in the particular environment. For example, gateway addresses, modems, RF network names, router addresses, etc. In addition, the environment profile may include a network configuration, such as but not limited to, encryption existence and type, default packet size, etc. 
     The information about the environment obtained by the environment detector  330  is transferred to the MDM  320 . The information may indicate the location of the client computer  110  or may indicate that the current location is unknown. Based on the current location, a security policy may be selected from the BOSP  340 . 
     The BOSP  340  manages one or more security policies that are installed from time to time by the administrator of the private network  120  ( FIG. 1 ), while the client computer  110  is connected over the private network  120 . The BOSP  340  may include policies that are relevant to certain locations, in which the client computer may be used. Moreover, the policy may be dependent upon the time of operation, the type of network, capabilities and types of external devices, the number of external devices, etc. In an exemplary embodiment, the different policies can be organized within the BOSP  340  using a hierarchic architecture. The top of the hierarchy may be the location, (e.g. at work, home, at a subsidiary, unknown place, etc). The second level of the hierarchy may be the network type and configuration (e.g. wired LAN, wireless LAN such as WiFi or Bluetooth or IR, public Internet, Intranet, encryption, etc). The third level may be the type of the external device (e.g. a removable storage device, removable storage media, a PDA, a cellular phone, WiFi dongle, Bluetooth dongle, a digital camera, etc.). Other exemplary methods may have additional levels or may organize the BOSP  340  using other architectures. 
     Each security policy may comprise a plurality of rules that may control a connection, or attributes of a connection, between a device and the client computer, and control the communication session between the device and the client computer. The rules may define: the maximum volume of data that can be transferred during a certain session; the maximum time for the session; the type of applications (e.g. read, write, synchronization etc.) that may be used; the type of files (e.g. word documents, email, markup language files, executable files, etc.) that may be transferred; the verification method that may be used during the session to verify that the device acts as expected. 
     From time to time, the content of the BOSP  340  may be checked and updated manually by the administrator of network  120  or automatically by the security server  130  ( FIG. 1 ). From time to time, the MDM  320  may check that the BOSP  340  has not been tampered with by hostile code. If the BOSP  340  has been damaged or otherwise altered, the MDM  320  may prevent any data transportation to/from any external device. More information on the operation of the BOSP  340  is disclosed below in conjunction with the discussion of  FIG. 5 . 
     The BOP  342  may comprise information that may be used for parsing the packets and reassembling the content of the data that is transferred during a certain session. In addition the BOP  342  may include rules for analyzing the content of the reassembled data. The information in the BOP  342  may be organized in a hierarchical architecture. The first level of the hierarchy may be associated with the type of the data communication port or bus  250   a - c  ( FIG. 2 ), (e.g. USB, FireWire, PCMCIA, SCSI, Infrared, wireless communication such as but not limited WiFi, Bluetooth, iSCSI, Cellular, Infiniband, Serial, Parallel, LAN port, Fiber Channel, etc). The second level of the hierarchy may be associated with the type of the external device (e.g. a removable storage device, removable storage media, a PDA, a cellular phone, WiFi dongle, Bluetooth dongle, a digital camera, etc.). The third level of the BOP  342  may be associated with the application that is currently used in the communication session. For example, synchronization, data storage or backup and communication applications. Other exemplary embodiments of the BOP  342  may include other levels or may be organized using other types of architectures. 
     For example, in case that a mass storage device, such as but not limited to DiskOnKey, is connected over a USB port, the first level of the BOP  342  may refer to a USB communication port. The USB entry may include information regarding parsing and reassembling the data that is associated with the physical layer of the communication over a USB port. The result of processing the packet according to the information that is stored in the first level of the BOP  342  may be the type of the device that is currently connected over the USB port (e.g. Digital camera, a DiskOnKey, WiFi dongle, Bluetooth dongle, etc.); the vendor ID; product ID, device class, device type, device description string, etc. 
     The information in the second level of the BOP  342  may refer to the type of the external device that is connected over the USB port. For example, in the scenario in which the external device is a DiskOnKey, the information in the second level of the BOP  342  may include information that is required to parse and reassemble the application layers of the communication. The third level includes information regarding the applications themselves, for instances the applications or operations may include, but not limited to, operations such as reading, writing, opening, closing, etc. 
     In another example, when a WiFi dongle is connected over a USB port, more protocol levels may be necessary than in the case of DiskOnKey. The WiFi dongle may allow communication over the Internet and thus, six protocol levels may be required and stored in the BOP  342  in order to parse, reassemble and analyze the communication that can be transferred via a WiFi dongle. The first level of the BOP  342  may refer to a USB communication port. The second level of the BOP  342  may refer to a WiFi protocol such as. but not limited to, IEEE 802.11B, the third level may refer to the Ethernet protocol, the level may refer to the Internet Protocol, the fifth level may refer to TCP or UDP or similar protocol and the sixth level may refer to the application itself, such as Microsoft Outlook, for example. More information on the operation of the BOP  342  is disclosed below in conjunction with the description of  FIG. 5 . 
     The TPC  350   a - c  is a temporary context that may be created by the MDM  320  according to the current needs of the communication session. The first TPC  350  may be initiated after receiving a notice from the transportation manager  310  that a communication session is requested via a communication port/bus  250   a - c . During initialization, the first context is established with parser  352 , reassembler  354  and analyzer  356  modules being loaded with the appropriate information. The information is loaded from the first level of the BOP  342  according to the type of the communication port/bus that is requested. 
     Additional contexts  350  may be issued during the flow of the communication by the MDM  320 . Usually a context  350   a - c  is associated with parsing, reassembling and analyzing a layer in the communication. Therefore when a TPC  350  collects enough information to define the next layer in the communication, it may inform the MDM  320  about the next layer. The information is collected from the buffer in which the packets are stored. In response, the MDM  320  may create the next TPC  350 . The MDM  320  may instruct the BOP  342  to transfer the next level of information to the new TPC  350 . The next level of information may include information on parsing, reassembling and analyzing the next communication layer that may be the device layer. At the end of the communication session, the one or more TPCx  350   a - c  may be released. 
     In some exemplary embodiments of the present invention TPC  350   a - c  may modify the content of the data. The modification may influence the type of the transportation. For example, a response to a question about the capabilities of a certain device driver may be modified to conceal the options of read and/or write. In other cases packets may be modified in order to be compatible with the protocol that is used. The modification may correct misuse or may avoid attack. More information on the operation of TPC  350   a - c  is disclosed below in conjunction with the discussion of  FIG. 5 . 
     The MDM  320  manages the operation of the security agent  230 . It may communicate with the security server  130  in order to download updated policies, run security tests, send reports to administrator, etc. From time to time, the MDM  320  may receive, from the ED  330 , information on the environment in which the client computer currently operates. When a communication session is initiated, the MDM  320  may receive an indication regarding the communication port  250  ( FIG. 2 ) that is associated with the session. Based on the communication port, the time of the session and the information regarding the current environment, the MDM  320  may select a security policy from the BOSP  340 . Subsequently, the MDM  320  can create a TPC  350  and instruct the BOP  342  to transfer the appropriate information that is relevant to the communication port to the new TPC  350 . When results are received from one of analyzers  356  running within a TPC  350 , the MDM  320  may analyze the results to reach a decision. The decision can be based, at least in part, on the selected security policy. The decision may be an instruction to the output controller  316  to indicate whether to transfer the packets from the buffers or to block the communication. A decision may include establishing an additional TPC  350  in order to process the next layer. A report may be issued by MDM  320 . From time to time the MDM  320  may request the ED  330  to initiate a learning cycle of the current environment, or the MDM  320  may initiate a task for checking the possibility that one or more of the modules of the security agent  230  may have been tampered with or altered. 
     A self-checker  333  may be invoked from time to time by the MDM  320  in order to verify that the security agent  230  has not been tampered with, altered or otherwise disrupted. The time intervals between activity cycles of the self-checker  333  may be in the range of few minutes to a few hours. Self-checker  333  may verify that the security agent  130  is still registered and the validity of the BOSP  340 . If a problem is identified, the MDM  320  may try to correct it, for example by registering again. If the problem cannot be corrected, the transportation via the relevant ports/buses may be blocked. 
     The History checker  336 , may be added, as an optional module, to the security agent  230 . From time to time, while the client computer  110  is connected over private network  120  ( FIG. 1 ), the History checker  336  may be invoked by security server  130  ( FIG. 1 ). The History checker  336  may check the operating system in order to verify the type of device drivers and the communication port drivers that have been active. The information about the history can be logged by the History checker  336 . This module may be used as a forensic tool that may deliver information to the security server  130  about the external devices that were connected to the computer client and the communication port that was used. 
     Another exemplary embodiment of the present invention may utilize more than one security agent module  230 . Each security agent module  230  may be associated with a communication port. Other exemplary embodiments may use one or more permanent TPC  350  modules instead of creating a required context when it is needed. Each module may be associated with a certain protocol and/or device and/or application. 
       FIG. 4  illustrates a flowchart depicting relevant steps of an exemplary method  400 . The method  400  may be used by the MDM  320  ( FIG. 3 ) for managing the input portion of data transportation via the security agent  230  ( FIG. 2 ). The method  400  may be initiated  410  when the client computer  110   a - c  ( FIG. 1 ) is turned on and may run as long as the computer  110   a - c  remains on. Upon initializing, the self-checker module  333  ( FIG. 3 ) may be invoked  412 . The self-checker  333  may operate to check whether the security agent  230  has been tampered with or modified. For example, by checking that the registration information in the Registry is appropriate. The results of the self checking are sent to the MDM  320 , which may use them in processing a decision of how to respond in certain data transfer sessions. At the end of the self-checker task  412  a timer is set to an initial value (0)  413 . The timer is used to define the period between repeating the self-checking process. 
     At step  415  in the illustrated flow diagram, a decision is made as to whether the client computer  110   a - c  is connected over the private network  120  ( FIG. 1 ). If the client computer  110   a - c  is connected over the private network  120 , the security agent  230  initiates a communication session  418  with the security server  130  via the private network  120 . The security agent  230  may send the result of the self-check to the security server  130  and deliver reports on the data transfer activity that has been done in the period between the last update and now. The report may include information on the files that were transferred, information on the devices that were used, the timing and the location of each data transfer session, shadowing information, etc. 
     During the communication session, the security server  130  may request the security agent  230  to perform additional tasks. For example, the security agent  230  may be requested to invoke the History checker module  336  in order to collect information on the different devices that have been registered between the last update and now. In addition, the security server  130  may update the BOSP  340  ( FIG. 3 ) in the security agent  300 . At the end of the communication session with the security server  130 , the method  400  may proceed to step  420 . 
     If it is determined at step  415  that the client computer  110   a - c  is not connected to private network  120 , then the method  400  may proceed to step  420  and wait for a data portion. The data portion may be a variety of packet types including, but not limited to, a packet for a USB communication port or a SCSI block for a SCSI bus, etc. When a data portion is received, a decision is made as to whether the data portion belongs to a new session  430 . This decision may be based, at least in part, on a connection table and the relevant source or destination addresses of the data portion, or the time slot that is associated with the data portion. The connection table may include information on the connections that are currently managed by the TM  310  ( FIG. 3 ). The information may include, but is not limited to, source and destination addresses, pointers in the buffer to the stored data that belongs to the session, port information, device information and application information, etc. The information from the connection table may also be used by other modules. Modules such as, but not limited to, the MDM  320 , one or more TPC  350   a - c  and OC  316 . 
     If it is determined that the session is a new session, then a new entry in the connection table is added, a new buffer is assigned to this session and the data portion is temporary stored in this buffer  434 . In parallel with these actions, a new session task is initiated in the MDM  320  in order to manage the handling of the new session. The session task may request information from the environment detector  330  and based on the current environment and the communication port, a security policy may be retrieved from BOSP  340  ( FIG. 3 ). 
     In addition to these actions, a new TPC  350  ( FIG. 3 ) is created to process the data and the appropriate protocol that matches the communication port is retrieved from BOP  342  ( FIG. 3 ). Later, the internal modules of TPC  350  (Parser  352 , Re-assembler  354  and Analyzer  356 ) are constructed with the appropriate software code to meet the specifications of the retrieved protocol. The new TPC receives the pointer to the stored data and starts processing the information. In parallel to the operation of the TPC, the method  400  may proceed and continue to step  440 . 
     In step  440 , the value of timer ‘T’ is compared to period ‘T1’. If timer ‘T’ is smaller than ‘T1’, then method  400  may return to step  420  and wait for the next data portion. If ‘T’ is equal to or greater than ‘T1’, than method  400  may return to step  412  and may invoke the self-checker module  333  again. Typical values of period ‘T1” may be in the range of few minutes to few hours. 
     If it is determined that the session  430  is not a new session, then the received data portion is stored in the appropriate buffer and a pointer is stored in the connection table  438 . The pointer is sent to the appropriate TPC  350  ( FIG. 3 ), which reviews the transportation of this session. The TPC  350  may retrieve the stored data portion when it is needed to be processed. 
       FIG. 5  illustrates a flowchart with the relevant steps of an exemplary method  500 . Method  500  may be used by the MDM  320  ( FIG. 3 ) for determining how to proceed with a session of data transportation that is currently transferred via the security agent  230  ( FIG. 2 ). Method  500  may be initiated  510  when the client computer  110   a - c  ( FIG. 1 ) is turned on and may run as long as the computer  110   a - c  is operating. Upon initializing, the MDM  320  ( FIG. 3 ) may wait for receiving an analysis report from one of the analyzers  356  that are currently active  520 . The report may be stored and a pointer may be added to the connection table. An analysis may include information on the data communication layer that is processed by the TPC  350 , to which the analyzer  356  belongs. For example, if the TPC that sent the report processes the layer of the communication port, then the report may include information on the port type, the type of the external device that is connected to the port, etc. If the level that is processed by the TPC is the device level, then the information may be on the type of application that is used. For example, if the device is a PDA, then the reports may indicate that the current application is a “synchronization application”, etc. 
     At step  525  the MDM  320  may retrieve the reports that are associated with a session. Retrieving the reports may be done by using the pointers that are stored in the connection table. The reports may be initiated by one or more TPCs that are associated with the session, which is currently under the decision process. The reports may deliver information, such as but not limited to, information on the communication port, the device, the application that is used and the type of data that is transferred. Based on the reports, the indication of the current environment and the relevant security policy, the MDM  320  may reach a decision  530  regarding how to proceed with the connection. 
     An exemplary security agent  230  may reach five types of decisions. The decisions may include: (a) blocking the data transportation  532 ; (2) enabling the data transportation  534 ; (3) creating an additional TPC  536 ; (4) waiting for an additional data portion  538 , or (5) ending the communication session  540 . 
     An example of a session that may be blocked by the security agent in step  532  may be a communication session in which the report from the TPC  350 , which analyzes the port level, indicates that the communication port is USB and the device is WiFi dongle, and the report from the TPC, which analyzes the device level, indicates that the application is an Email application. Another example of a session that may be blocked at step  532  by the security agent  230  is a communication session in which the report from the TPC  350 , which analyzes the port level, indicates that the communication port is SCSI and the device is removable disc driver; the report from the TPC, which analyzes the device level, indicates that the application is “Write to Disc”. 
     Upon receiving a decision to block the data transfer of the current session, an instruction is sent to OC  316  instructing it to maintain the connection without transferring the information. For example, OC  316  may send an indication to the destination that the requested information is not found. In addition, information about the session may be stored in a report that may be sent to the security server  130 . The information may be about the content, the time, the driver and the application that were used, the location, etc. The resources of the security agent  230  that have been allocated to this session may remain active in order to monitor other communication portions in the continuation of the session. For example, the application may be changed from copy information to synchronize a PDA. The new application (synchronization) may be allowed. Then the MDM  320  may return to step  520  and wait to the next analysis report. 
     An example of a session, which may be open (allowed) by the security agent  230  at step  534 , may be a communication session in which the report from the TPC  350 , which analyzes the port level, indicates that the communication port is USB and the device is a flash memory device, such as but not limited to DiskOnKey and the report from the TPC  350 , which analyzes the device level, discloses identification parameters of the DiskOnKey. The session may be allowed if a DiskOnKey with the same identification parameters is allowed by the appropriate security policy. 
     Upon receiving a decision to open the data transfer of the current session  534 , an instruction is sent to OC  316  instructing it to retrieve the appropriate data portions from the appropriate location in the buffer and transfer them toward their destination. Information about the appropriate location in the buffer and the destination may be found in the connection table. In parallel to sending the data to its destination, a copy of the data may be stored for shadowing. The instruction for shadowing may be written in the policy that is used. Shadowing may be stored in a location in the disc that cannot be accessed by the user. Indication about this session may be stored in a report that may be sent to the security server  130 . The resources of the security agent that have been allocated to this session may remain active in order to monitor changes in the session. Then the MDM  320  may return to step  520  and wait for the reception of the next analysis report. 
     An example of a decision for initiating an additional TPC  536  may be reached when a report from the TPC  350 , which analyzes the port level, indicates that the communication port is a USB port and that the device is a Bluetooth dongle, for example. Then a decision may be determined to initiate an additional TPC for processing the Bluetooth section of the data communication. A security policy that matches the Bluetooth device with or without the current environment may be loaded into the MDM  320 . The appropriate protocol may be loaded to the new parser  352  ( FIG. 3 ) and re-assembler  354 . Information about analyzing the Bluetooth information is loaded into the analyzer  356 . The previous TPC (the port TPC), may be instructed to transfer the appropriate section of the data to the new TPC for additional processing. Then the MDM  320  may return to step  520  to wait for the reception of the next analysis report. In some cases, additional information is needed in order to reach a decision  538 . When this occurs, the MDM  320  may return to step  520  and wait for an additional analysis report. For example, this may occur under the scenario in which the application is “Write” to a DiskOnKey and the security policy requires checking of “Water Marks” in the content of the file. In this scenario, the MDM  320  may wait until the entire content of the file has been analyzed. “Water Marks” are “undetectable” digital images with 8 bit gray scales. The watermark is capable of carrying such information as authentication or authorization codes, or even a legend essential for image interpretation. This capability is envisaged to find application in image tagging, copyright enforcement, counterfeit protection, and controlled access to image data. 
     If the report that is received from the TPC, which processes the port level information, indicates that the communication session has been terminated  540 , then the MDM  320  may release the resources that have been associated with the session. The resources may include, but are not limited to, the buffers and the one or more TPCs that have been associated with the session, etc. Then the MDM  320  may return to step  520  and wait to the next analysis report from another data communication session. 
     In this application the words “unit” and “module” are used interchangeably. Anything designated as a unit or module may be a stand-alone unit or a specialized module. A unit or a module may be modular or have modular aspects allowing it to be easily removed and replaced with another similar unit or module. Each unit or module may be any one of, or any combination of, software, hardware, and/or firmware 
     In the description and claims of the present application the word WiFi is used to represent all types of Wireless LANs and not only 802.11b networks (for example it represents among others 802.11g, 802.11a, 802.16 etc). 
     In the description and claims of the present application, the word computer or client computer represent any end device, which has computing power. It includes among others cellular phones, PDAs, and other types of end equipment with a CPU that controls its behavior and communication. 
     In the description and claims of the present application, each of the verbs, “comprise” “include” and “have”, and conjugates thereof, are used to indicate that the object or objects of the verb are not necessarily a complete listing of members, components, elements, or parts of the subject or subjects of the verb. 
     The present invention has been described using detailed descriptions of embodiments thereof that are provided by way of example and are not intended to limit the scope of the invention. The described embodiments comprise different features, not all of which are required in all embodiments of the invention. Some embodiments of the present invention utilize only some of the features or possible combinations of the features. Variations of embodiments of the present invention that are described and embodiments of the present invention comprising different combinations of features noted in the described embodiments will occur to persons of the art. The scope of the invention is limited only by the following claims.