Abstract:
A method includes receiving from a client device at a client interface application a request to access an application, determining whether the application is external to a communication network, redirecting the request to an external communication server when the application is external to the communication network, sending the request from the external communication server to the application that is external to the communication network, receiving information from the application that is external to the communication network at the external communication server responsive to sending the request, and replicating a screen of the external communication server containing the information received from the application for display at the client interface application.

Description:
BACKGROUND 
       [0001]    The present disclosure relates generally to computer system and network security and, more particularly, to methods, systems, computer program products for protecting a communication network against Advanced Persistent Threats (APTs) by controlling the vectors of potential data exfiltration. 
         [0002]    Advanced Persistent Threats (APTs) are one of the fastest growing information security threats that organizations face today. The goals of an APT are typically to steal intellectual property (IP), generated from expensive research, from a targeted organization, to gain access to sensitive customer data, and/or to access strategic business information that could be used for financial gain, blackmail, embarrassment, data poisoning, illegal insider trading and/or to disrupt an organization&#39;s business. APTs have become very sophisticated and diverse in the methods and technologies used, particularly in the ability to use an organization&#39;s own employees to penetrate the information technology (IT) systems by using social engineering methods. APTs may trick users into opening spear phishing emails, which install specially crafted and customized malware that may contain code to exploit zero-day vulnerabilities in the targeted system.  FIG. 1  shows the typical attack infrastructure and how the APT operators carry out most APTs. First, an APT operator, from, for example, an overseas network, launches an attack campaign to compromise public vulnerable servers  150   a ,  150   b , and  150   c . Then, the APT operator manually crafts and sends a customized spear phishing email through one or more of the compromised public servers  150   a ,  150   b , and  150   c  that may contain a malicious URL or attachment that, once clicked, will install a Remote Access Trojan (RAT) on a target device, such as device  160 . From this point forward, the attackers have full access to the victim device  160  and to all the data the victim can access. Usually, over a long period of time, the APT operators will manually execute commands, such as command and control (C&amp;C) commands, and will move laterally into the victim&#39;s network, compromising other internal resources, such as internal server  165 , until they reach the targeted internal resources or data. The data may then be exfiltrated back through the compromised servers  150   a ,  150   b , and  150   c  and made available to the APT operator. 
         [0003]    APT protection effort has focused on stopping malware from entering the enterprise perimeter. A potential problem with this approach is that there may be too many vectors of infection (e.g. email attachments, malicious URLs, USB drives, etc.) and in most cases APT operators use zero day exploits that are not detectable by traditional perimeter based systems. Moreover, once a device is compromised and the APT operators have a foothold in the organization network, there are too many possible outgoing vectors for data exfiltration (e.g. email, raw IP connections, USB drives, etc.). The same problems may persist when the enterprise is moved into the cloud and virtualized apps or desktops are used to access corporate data. 
         [0004]    Cloud computing is a computing paradigm where shared resources, such as processor(s), software, and information, are provided to computers and other devices on demand typically over a network, such as the Internet. In a cloud computing environment, details of the computing infrastructure, e.g., processing power, data storage, bandwidth, and/or other resources are abstracted from the user. The user does not need to have any expertise in or control over such computing infrastructure resources. Cloud computing typically involves the provision of dynamically scalable and/or virtualized resources over the Internet. A user may access and use such resources through the use of a Web browser. A typical cloud computing provider may provide an online application that can be accessed over the Internet using a browser. The cloud computing provider, however, maintains the software for the application and some or all of the data associated with the application on servers in the cloud, i.e., servers that are maintained by the cloud computing provider rather than the users of the application. 
         [0005]      FIG. 2  illustrates a conventional cloud service model that includes Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS). Infrastructure as a Service, delivers computer infrastructure—typically a platform virtualization environment—as a service. Rather than purchasing servers, software, data-center space or network equipment, clients instead buy those resources as a fully outsourced service. Suppliers typically bill such services on a utility computing basis and the amount of resources consumed. Platform as a Service delivers a computing platform as a service. It provides an environment for the deployment of applications without the need for a client to buy and manage the underlying hardware and software layers. Software as a Service delivers software services over the Internet, which reduces or eliminates the need for the client to install and run an application on its own computers, which may simplify maintenance and support. 
         [0006]    Virtualized computing environments may be used to provide computing resources to end users. In a cloud computing environment, the physical hardware configuration is hidden from the end user. Cloud computing systems may include servers, network storage devices, routers, gateways, communication links, and other devices. Because the physical hardware and software platforms on which cloud computing system is implemented are hidden within a “cloud,” they can be managed, upgraded, replaced or otherwise changed by a system administrator without the customer being aware of or affected by the change. 
         [0007]    In a typical cloud computing environment, applications may be executed on virtual machines, which are isolated guest operating systems installed within a host system. Virtual machines are typically implemented with either software emulation or hardware virtualization, or both. A single hardware and/or software platform may host a number of virtual machines, each of which may have access to some portion of the platform&#39;s resources, such as processing resources, storage resources, etc. 
         [0008]      FIG. 3  illustrates a server system  100  for a virtualized computing environment in which the inventive subject matter of the present disclosure can function. The server system  100  generally hosts one or more virtual machines  104  (hereafter virtual machine  104 ), each of which runs a guest operating system  106  and application  108 . The computing needs of users  102  drive the functionality of the virtual machines  104 . A virtual hypervisor  110  provides an interface between the virtual machines  104  and a host operating system  112  and allows multiple guest operating systems  106  and associated applications  108  to run concurrently. The host operating system  112  handles the operations of a hardware platform  114  capable of implementing virtual machines  104 . A data storage space  116  may be accessed by the host operating system  112  and is connected to the hardware platform  114 . 
         [0009]    The hardware platform  114  generally refers to any computing system capable of implementing virtual machines  104 , which may include, without limitation, a mainframe, personal computer (PC), micro-computer, handheld computer, mobile computing platform, server, or any other appropriate computer hardware. The hardware platform  114  may include computing resources, such as a central processing unit (CPU); networking controllers; communication controllers; a display unit; a program and data storage device; memory controllers; input devices (e.g., a keyboard, a mouse, etc.) and output devices, such as printers. The CPU may be any conventional processor, such as the AMD Athlon™ 64, or Intel® Core™ Duo. 
         [0010]    The hardware platform  114  may be further connected to the data storage space  116  through serial or parallel connections. The data storage space  116  may be any suitable device capable of storing computer-readable data and instructions, and it may include logic in the form of software applications, random access memory (RAM), or read only memory (ROM), removable media, or any other suitable memory component. According to the illustrated embodiment, the host operating system  112  stands between the hardware platform  114  and the users  102  and is responsible for the management and coordination of activities and the sharing of the computing resources. In other embodiments, the virtual hypervisor runs directly on the hardware  114  without the intervening host operating system  112 . 
         [0011]    Although some embodiments of the computer system  100  can be configured to operate as a computer server, the computer system  100  is not limited thereto and can be configured to provide other functionality, such as data processing, communications routing, etc. 
         [0012]    Besides acting as a host for computing applications that run on the hardware platform  114 , the host operating system  112  may operate at the highest priority level in the server  100 , executing instructions associated with the hardware platform  114 , and it may have exclusive privileged access to the hardware platform  114 . The priority and privileged access of hardware resources affords the host operating system  112  exclusive control over resources and instructions, and may preclude interference with the execution of different application programs or the operating system. The host operating system  112  creates an environment for implementing a virtual machine, hosting the “guest” virtual machine. One host operating system  112  is capable of implementing multiple isolated virtual machines simultaneously. 
         [0013]    A virtual hypervisor  110  (which may also be known as a virtual machine monitor or VMM) runs on the host operating system  112  and provides an interface between the virtual machines  104  and the hardware platform  114  through the host operating system  112 . The virtual hypervisor  110  virtualizes the computing system resources and facilitates the operation of the virtual machines  104 . The hypervisor  110  may provide the illusion of operating at the highest priority level to the guest operating systems  106 . The virtual hypervisor  110  maps the guest operating system&#39;s priority level to a priority level lower than the top most priority level. As a result, the virtual hypervisor  110  can intercept the guest operating system  106  to execute instructions that require virtualization assistance. Alternatively, the virtual hypervisor  110  may emulate or actually execute the instructions on behalf of the guest operating system  106 . Software operations permitting indirect interaction between the guest operating system  106  and the physical hardware platform  114  are also performed by the virtual hypervisor  110 . 
         [0014]    Virtual machines  104  present a virtualized environment to guest operating systems  106 , which in turn provide an operating environment for applications  108  and other software constructs. 
         [0015]    Referring to  FIG. 4 , a virtualized computing environment  200  (referred to generally as cloud  200 ) may include one or more server systems  100  that may include one or more electronic computing devices operable to receive, transmit, process, and store data. For example, the servers in the cloud  200  may include one or more general-purpose PCs, Macintoshes, micro-computers, workstations, Unix-based computers, server computers, one or more server pools, or any other suitable devices. In certain embodiments, the cloud  200  may include a web server. In short, the cloud  200  may include any suitable combination of software, firmware, and hardware. 
         [0016]    The cloud  200  may include a plurality of server systems  100  that are communicatively coupled via a network  112 . The network  112  facilitates wireless or wireline communication, and may communicate using, for example, IP packets, Frame Relay frames, Asynchronous Transfer Mode (ATM) cells, voice, video, data, and other suitable information between network addresses. The network  112  may include one or more local area networks (LANs), radio access networks (RANs), metropolitan area networks (MANS), wide area networks (WANs), all or a portion of the global computer network known as the Internet, and/or any other communication system or systems at one or more locations. Although referred to herein as “server systems,” it will be appreciated that any suitable computing device may be used. 
         [0017]    Virtual machines and/or other objects in a virtualization environment can be grouped into logical clusters for management and/or operational purposes. For example, virtual machines can be grouped into clusters based on load balancing needs, security needs, redundancy needs, or any other needs as determined by a system administrator. The virtual machines grouped within a cluster may or may not all be implemented on a single physical server. Any desired number of clusters can be defined subject to system limitations, and each of the clusters can include any desired number of virtual machines subject to server limitations. 
         [0018]    Virtual machines can be deployed in particular virtualization environments and organized to increase the efficiency of operating and/or managing a virtual computing environment. For example, virtual machines may be grouped into clusters to provide load balancing across multiple servers. 
         [0019]    Virtual machines within a same cluster can be managed by a single virtualization environment manager to have same or similar resource access privileges (e.g., processor utilization, priority, memory allocation, communication interface access privileges, etc.), while virtual machines within different clusters can have different resource access privileges. 
         [0020]    Virtual machines that are deployed within a single cluster may share physical resources within a server. For example, virtual machines that are deployed within a single cluster may share physical memory, storage, communication facilities and other resources or services of a server. Whenever computing resources are shared, there is the possibility that one virtual machine could intentionally or unintentionally gain access to data of another virtual machine 
       SUMMARY 
       [0021]    It should be appreciated that this Summary is provided to introduce a selection of concepts in a simplified form, the concepts being further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of this disclosure, nor is it intended to limit the scope of the disclosure. 
         [0022]    Some embodiments provide a method comprising receiving from a client device at a client interface application a request to access an application, the client interface application being accessible to the client device, determining whether the application is external to a communication network, redirecting the request to an external communication server when the application is external to the communication network, sending the request from the external communication server to the application that is external to the communication network, receiving information from the application that is external to the communication network at the external communication server responsive to sending the request, and replicating a screen of the external communication server containing the information received from the application for display at the client interface application. 
         [0023]    In other embodiments, the client interface application is a Web browser application and the request is a Hypertext Transfer Protocol based request. 
         [0024]    In still other embodiments, replicating the screen of the external communication server comprises replicating the screen of the external communication server using Remote Desktop Protocol. 
         [0025]    In still other embodiments, the method further comprises redirecting the request to an internal server on which the application resides when the application is internal to the communication network. 
         [0026]    In still other embodiments, the method further comprises receiving information from the application that is internal to the communication network at the client interface application responsive to the internal server receiving the request. 
         [0027]    In still other embodiments, the method further comprises receiving from the client device at an electronic mail application an electronic mail request, forwarding the electronic mail request to an internal electronic mail server that is internal to the communication network, determining at the internal electronic mail server whether the electronic mail request is directed to an external electronic mail server that is external to the communication network, determining whether the electronic mail request violates an electronic mail policy when the electronic mail request is directed to the external electronic mail server, and blocking the electronic mail request at the internal electronic mail server when the electronic mail request violates the electronic mail policy. 
         [0028]    In still other embodiments, the client interface application is provided through a hosted virtual desktop environment. 
         [0029]    In further embodiments, a system comprises a processor and a memory that is coupled to the processor. The memory comprises computer readable program code that when executed by the processor causes the processor to perform operations comprising receiving from a client device at a client interface application a request to access an application, the client interface application being accessible to the client device, determining whether the application is external to a communication network, redirecting the request to an external communication server when the application is external to the communication network, sending the request from the external communication server to the application that is external to the communication network, receiving information from the application that is external to the communication network at the external communication server responsive to sending the request, and replicating a screen of the external communication server containing the information received from the application for display at the client interface application. 
         [0030]    In still further embodiments, the client interface application is a Web browser application and the request is a Hypertext Transfer Protocol based request. 
         [0031]    In still further embodiments, replicating the screen of the external communication server comprises replicating the screen of the external communication server using Remote Desktop Protocol. 
         [0032]    In still further embodiments, the operations further comprise redirecting the request to an internal server on which the application resides when the application is internal to the communication network. 
         [0033]    In still further embodiments, the operations further comprise receiving information from the application that is internal to the communication network at the client interface application responsive to the internal server receiving the request. 
         [0034]    In still further embodiments, the operations further comprise receiving from the client device at an electronic mail application an electronic mail request, forwarding the electronic mail request to an internal electronic mail server that is internal to the communication network, determining at the internal electronic mail server whether the electronic mail request is directed to an external electronic mail server that is external to the communication network, determining whether the electronic mail request violates an electronic mail policy when the electronic mail request is directed to the external electronic mail server, and blocking the electronic mail request at the internal electronic mail server when the electronic mail request violates the electronic mail policy. 
         [0035]    In still further embodiments, the client interface application is provided through a hosted virtual desktop environment. 
         [0036]    In other embodiments, a computer program product comprises a tangible computer readable medium comprising computer readable program code embodied in the medium that when executed by a processor causes the processor to perform operations comprising receiving from a client device at a client interface application a request to access an application, the client interface application being accessible to the client device, determining whether the application is external to a communication network, redirecting the request to an external communication server when the application is external to the communication network, sending the request from the external communication server to the application that is external to the communication network, receiving information from the application that is external to the communication network at the external communication server responsive to sending the request, and replicating a screen of the external communication server containing the information received from the application for display at the client interface application. 
         [0037]    In still other embodiments, the client interface application is a Web browser application and the request is a Hypertext Transfer Protocol based request. 
         [0038]    In still other embodiments, replicating the screen of the external communication server comprises replicating the screen of the external communication server using Remote Desktop Protocol. 
         [0039]    In still other embodiments, the operations further comprise redirecting the request to an internal server on which the application resides when the application is internal to the communication network. 
         [0040]    In still other embodiments, the operations further comprise receiving information from the application that is internal to the communication network at the client interface application responsive to the internal server receiving the request. 
         [0041]    In still other embodiments, the operations further comprise receiving from the client device at an electronic mail application an electronic mail request, forwarding the electronic mail request to an internal electronic mail server that is internal to the communication network, determining at the internal electronic mail server whether the electronic mail request is directed to an external electronic mail server that is external to the communication network, determining whether the electronic mail request violates an electronic mail policy when the electronic mail request is directed to the external electronic mail server, and blocking the electronic mail request at the internal electronic mail server when the electronic mail request violates the electronic mail policy. 
         [0042]    Other methods, systems, articles of manufacture, and/or computer program products according to embodiments of the invention will be or become apparent to one with skill in the art upon review of the following drawings and detailed description. It is intended that all such additional systems, methods, and/or computer program products be included within this description, be within the scope of the present invention, and be protected by the accompanying claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0043]    Other features of exemplary embodiments will be more readily understood from the following detailed description of specific embodiments thereof when read in conjunction with the accompanying drawings, in which: 
           [0044]      FIG. 1  is a block diagram of a communication network that illustrates a typical attack infrastructure for an Advanced Persistent Threat (APT) operator; 
           [0045]      FIG. 2  is a block diagram that illustrates cloud computing paradigm; 
           [0046]      FIG. 3  is a block diagram that illustrates a virtualized computing environment; 
           [0047]      FIG. 4  is a block diagram that illustrates a cloud computing environment; 
           [0048]      FIG. 5  is a block diagram of a communication network in which screen replication from controlled public network access points is used to reduce the effects of Internet enabled cyber attacks according to some embodiments; 
           [0049]      FIG. 6  is a block diagram that illustrates the architecture of the client interface server, the internal resource server, and the external communication server according to some embodiments; and 
           [0050]      FIGS. 7 and 8  are flowcharts that illustrate operations for reducing the effects of Internet enabled cyber attacks according to some embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0051]    As will be appreciated by one skilled in the art, aspects of the present disclosure may be illustrated and described herein in any of a number of patentable classes or contexts including any new and useful process, machine, manufacture, or composition of matter, or any new and useful improvement thereof. Accordingly, aspects of the present disclosure may be implemented entirely hardware, entirely software (including firmware, resident software, micro-code, etc.) or combining software and hardware implementation that may all generally be referred to herein as a “circuit,” “module,” “component,” or “system.” Furthermore, aspects of the present disclosure may take the form of a computer program product comprising one or more computer readable media having computer readable program code embodied thereon. 
         [0052]    Any combination of one or more computer readable media may be used. The computer readable media may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an appropriate optical fiber with a repeater, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. 
         [0053]    A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. Program code embodied on a computer readable signal medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing. 
         [0054]    Computer program code for carrying out operations for aspects of the present disclosure may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Scala, Smalltalk, Eiffel, JADE, Emerald, C++, C#, VB.NET, Python or the like, conventional procedural programming languages, such as the “C” programming language, Visual Basic, Fortran 2003, Pal, COBOL 2002, PHP, ABAP, dynamic programming languages such as Python, Ruby and Groovy, or other programming languages. The program code may execute entirely on the user&#39;s computer, partly on the user&#39;s computer, as a stand-alone software package, partly on the user&#39;s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user&#39;s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider) or in a cloud computing environment or offered as a service such as a Software as a Service (SaaS). 
         [0055]    Aspects of the present disclosure are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the disclosure. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable instruction execution apparatus, create a mechanism for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
         [0056]    These computer program instructions may also be stored in a computer readable medium that when executed can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions when stored in the computer readable medium produce an article of manufacture including instructions which when executed, cause a computer to implement the function/act specified in the flowchart and/or block diagram block or blocks. The computer program instructions may also be loaded onto a computer, other programmable instruction execution apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatuses or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
         [0057]    Some embodiments stem from a realization that a communication network, such as an enterprise network, can be configured to separate corporate resources and data from outbound access to an external network, such as the Internet, and allow external network access only through a limited number of controlled paths. For example, when a user wishes to access the Internet the user may use a dedicated and controlled path to a web browser that runs in an external communication server, which may be a separate virtual machine. Therefore no raw external Internet Protocol (IP) connections to the Internet may be allowed from the environment where the enterprise data is located. Client devices may have access to client interface applications (e.g., virtualized desktop) using some type of network (e.g., mobility, Wi-Fi, or wired broadband) over a screen replication protocol, such as Remote Desktop Protocol (RDP). The screen replication protocol is used to ensure only screenshots are sent back from the external communication server to other servers in the enterprise network and from the client interface applications to the client devices, which also may be untrusted. Thus, while the external communication server may be vulnerable to an Advanced Persistent Threat (APT) attack, the intrusion can be confined to the external communication as screen replication is used between the external communication server and other servers and systems in the enterprise network. Moreover, the external communication server can be re-started with a fresh-image frequently to remove persistent malware. 
         [0058]    Referring now to  FIG. 5 , a communication network  500  includes both an enterprise network  510  and a public network  515 . The public network  515  may represent a global network, such as the Internet, or other publicly accessible network. Furthermore, the public network  515  may represent a combination of public and private networks or a virtual private network (VPN). The enterprise network  510  may represent a wide area network, a local area network, an Intranet, or other private network, which may not accessible by the general public. The enterprise network  510  includes a client interface server  520 , an internal resource server  525 , an external communication server  530 , and an electronic mail server  535  that are connected as shown. Each of the client interface server  520 , the internal resource server  525 , the external communication server  530 , and the electronic mail server  535  may be implemented as a single server, separate servers, or a network of servers either co-located in a server farm, for example, or located in different geographic regions. In some embodiments, these servers may be implemented as virtual servers on a single hardware platform. 
         [0059]    The communication network  500  further comprises mobile devices  540   a  and  540   b  that communicate with the client interface server  520  in the enterprise network  510  over a variety of types of networks  545  including, but not limited to, cellular, WiFi, and wired broadband. It will be further understood that client devices may also communicate with the client interface server  520  through wired connections. 
         [0060]    The client interface server  520  may support one or more virtualized client interface applications, for example, that may service requests from client devices  540   a  and  540   b . The client interface server  520  is equipped with a memory  550  that is representative of the one or more memory devices containing the software and data used to decide whether to rout client requests for an application to an internal enterprise network  510  resource or to an application that is external to the enterprise network  510 . As shown in  FIG. 5 , the memory  550  may contain a decision manager module  555  that may be used to evaluate requests received from client devices, such as client devices  540   a  and  540   b , and determine whether the requests are for applications or resources internal to the enterprise network  510 —in which case the request may be routed to the internal resource server  525 —or if the requests are for applications or resources external to the enterprise network  510 —in which case the request may be routed to the external communication server  530 . The virtualized client interface application(s) may route electronic mail requests to the electronic mail server  535 . 
         [0061]    The external communication server  530  may be configured as a virtual server that handles requests for applications external to the enterprise network  510 . For example, if a client device uses a Web browser application to generate a Hypertext Transfer Protocol based request to access an external website, the external communication server  530  may communicate with the external server  560  in the public network  515  to access the website. Because the external server  560  is in public network  515  and is vulnerable to APT attacks as described above, the external communication server  530  may provide the obtained website information back to the client device using screen replication, such as that provided through RDP. Because only screen shots are sent back to the client device, an APT operator can only penetrate the external communication server  530  in the enterprise network  510  thereby protecting other servers and resources in the enterprise network  510 . 
         [0062]    The electronic mail server  535  may be configured to handle electronic mail requests from client devices, such as client devices  540   a  and  540   b . The electronic mail requests may be serviced internal to the enterprise network  510  at the electronic mail server  535  or the requests may involve the electronic mail server  535  communicating with an external electronic mail server  570  that is located in the public network  515 . The electronic mail server  575  is equipped with a memory  575  that is representative of the one or more memory devices containing the software and data used to apply policies or rules defined, for example, by the operator of the enterprise network  510  for managing, sending, and/or receiving email in the enterprise. As shown in  FIG. 5 , the memory  575  may contain a policy manager module  580  that may evaluate electronic mail requests and determine whether the electronic mail requests violate the policies or rules defined by the enterprise. For example, the policy manager module  580  may block an electronic mail request that seeks to download an electronic mail message from the external electronic mail server  570  to the electronic mail server  535  that contains an attachment that is a virus or some other type of malware. By using the policy manager  580  to manage access to the external electronic mail server  570 , the risk of a successful attack from an APT operator or other hostile party on the enterprise through the email system can be reduced. 
         [0063]    Although  FIG. 5  illustrates an exemplary communication network and an exemplary hardware/software architecture that may be used in data processing systems, such as the client interface server  520  and the electronic mail server  535  for protecting an enterprise network against attacks by APT operators or other hostile parties, it will be understood that embodiments of the present invention are not limited to such a configuration but are intended to encompass any configuration capable of carrying out operations as described herein. Moreover, the functionality of the client interface server  520  and the electronic mail server  535  of  FIG. 5  may be implemented as a single processor system, a multi-processor system, a multi-core processor system, or even a network of stand-alone computer systems, in accordance with various embodiments. 
         [0064]    Computer program code for carrying out operations of data processing systems and servers described above with respect to  FIG. 5 , such as the anomaly detection server  160 , may be written in a high-level programming language, such as Java, C, and/or C++, for development convenience. In addition, computer program code for carrying out operations of embodiments of the present invention may also be written in other programming languages, such as, but not limited to, interpreted languages. Some modules or routines may be written in assembly language or even micro-code to enhance performance and/or memory usage. Embodiments described herein, however, are not limited to any particular programming language. It will be further appreciated that the functionality of any or all of the program modules may also be implemented using discrete hardware components, one or more application specific integrated circuits (ASICs), or a programmed digital signal processor or microcontroller. 
         [0065]      FIG. 6  is a block diagram that further illustrates the architecture of the client interface server  520 , internal resource server  525 , and external communication server  530  according to some embodiments. As shown in  FIG. 6 , virtualized applications  610 , which may be embodied as a hosted virtualized desktop, may reside on the client interface server  520  and may provide a portal to the enterprise network for client devices. Requests from the client devices are processed by the decision manager module  655 , which corresponds to the decision manager module  555  of  FIG. 5 , to determine if the request is for access to an application or resource internal to the enterprise network or external to the enterprise network. If the request is for an application or resource internal to the enterprise network, then the request is forwarded to the internal enterprise resource server  625 , which corresponds to the internal resource server  525  of  FIG. 5 , for processing. The virtualized applications  610  may exchange data with applications and other resources on the internal resource server  625 . A screen replication protocol, such as RDP, may be used, however, to communicate data from the virtualized applications back to the client devices as the client devices may be untrusted entities and the enterprise may not wish for its actual data to be stored on mobile devices. If the request is for an application or resource that is external to the enterprise network, then the request is forwarded to the external communication server  630 , which corresponds to the external communication server  530  of  FIG. 5 . The external communication server  630  communicates with an external server in a public network, such as the Internet, to obtain data, such as Web browser data, to service the request. The external communication server  630  uses a screen replication protocol, such as RDP, to provide the data obtained in the public network back to the virtualized applications  610 . As a result, if the data obtained from the public network contains a virus or other type of malware, the virus/malware is not allowed to penetrate farther into the enterprise network beyond the external communication server  630 . 
         [0066]    Exemplary embodiments are described herein with reference to flowchart and/or block diagram illustrations of methods, systems, and computer program products in accordance with some embodiments. These flowchart and/or block diagrams further illustrate exemplary operations for protecting an enterprise network against attacks by APT operators or other hostile parties, in accordance with some embodiments. It will be understood that each block of the flowchart and/or block diagram illustrations, and combinations of blocks in the flowchart and/or block diagram illustrations, may be implemented by computer program instructions and/or hardware operations. These computer program instructions may be provided to a processor of a general purpose computer, a special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means and/or circuits for implementing the functions specified in the flowchart and/or block diagram block or blocks. 
         [0067]    These computer program instructions may also be stored in a computer usable or computer-readable memory that may direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer usable or computer-readable memory produce an article of manufacture including instructions that implement the function specified in the flowchart and/or block diagram block or blocks. 
         [0068]    The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions that execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart and/or block diagram block or blocks. 
         [0069]    Referring now to  FIGS. 5 and 7 , exemplary operations for protecting an enterprise network against attacks by APT operators or other hostile parties begin at block  700  where the client interface server  520  receives an application access request at a client interface application, which may be provided as part of a hosted virtualized desktop environment in some embodiments. The decision manager module  555  determines at block  705  whether the request involves access to an application or resource external to the enterprise network  510 , such as, for example, a Web server in the public network  515 . If the request does not involve access to an application or resource external to the enterprise network  510 , then the request is re-directed to the internal resource server  525  for processing at block  710 . 
         [0070]    If, however, the request does involve access to an application or resource external to the enterprise network  510 , then the request is re-directed to the external communication server  530  at block  715 , which then sends the request to the external server  560  in the public network  515  for processing at block  720 . Information from the application in the external server  560  is received back at the external communication server  530  at block  725 . Because the information received from the external server  560  in the public network  515  is susceptible to containing a virus or other type of malware generated, for example, by an APT operator, a screen replication protocol, such as RDP, may be used to provide the information back to the client device through the client interface application in the client interface server  520  at block  730 . Although the external communication server  530  may become infected with malware from a hostile party, the malware is confined to the external communication server  530  and not allowed to penetrate further into the enterprise network  510 . Moreover, the external communication server  530  may be frequently re-imaged to viruses and malware acquired from the public network  115 . 
         [0071]    Referring now to  FIGS. 5 and 8 , exemplary operations for protecting an enterprise network against attacks by APT operator or other hostile parties through electronic mail begin at block  800  where the client interface server  520  receives a request to access an electronic mail interface application, which may be provided as part of a hosted virtualized desktop environment in some embodiments. The request is forwarded to the electronic mail server  535  at block  805  for processing. The electronic mail server  805  determines at block  810  whether the request involves access to the external electronic mail server  570  in the public network  515 . If the request does not involve access to the external electronic mail server  570 , then the electronic mail request is processed at the electronic mail server  535  at block  815 . 
         [0072]    If, however, the electronic mail request does involve access to the external electronic mail server  570 , then the policy manager module  580  determines at block  820  whether the electronic mail request violates any policies or rules that the enterprise has defined for their electronic mail service. If the request does not violate any policies or rules, then the email request is forwarded from the electronic mail server  535  to the external electronic mail server  570  for processing at block  825 . If, however, the request does violate one or more policies or rules, then the email request is blocked at the electronic mail server  535  from reaching the external electronic mail server  570  at block  830 . An enterprise may use the policies and rules to carefully monitor what email is brought into the enterprise from the public network  515  and also what data and information is sent out from the enterprise into the public network. Thus, if an APT or hostile party were able to infect the enterprise network with a virus that collects confidential information and then emails the confidential information out of the enterprise, then the policies and rules enforced by the policy manager  580  may be able to block the sending of the confidential information at the electronic mail server  535 , which is internal to the enterprise. 
         [0073]    The flowcharts of  FIGS. 7 and 8  illustrate the architecture, functionality, and operations of some embodiments of methods, systems, and computer program products for protecting an enterprise network against attacks by APT operators or other hostile parties. In this regard, each block represents a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that in other implementations, the function(s) noted in the blocks may occur out of the order noted in  FIGS. 7 and 8 . For example, two blocks shown in succession may, in fact, be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending on the functionality involved. 
         [0074]    According to some embodiments described above, an enterprise may not allow arbitrary connections, such as IP connections, from its internal network to an external network where sensitive or protected data may be accessed by a potentially hostile party. A screen replication protocol, such as RDP, may be used to provide access to data and/or information that is obtained from an external source to prevent the spread of any intrusion from moving beyond an external communication server into other servers and resources in the enterprise network. 
         [0075]    The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various aspects of the present disclosure. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions. 
         [0076]    The terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. Furthermore, “connected” or “coupled” as used herein may include wirelessly connected or coupled. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Like reference numbers signify like elements throughout the description of the figures. 
         [0077]    Many variations and modifications can be made to the embodiments without substantially departing from the principles of the present invention. All such variations and modifications are intended to be included herein within the scope of the present invention, as set forth in the following claims.