Abstract:
Techniques used in a network that includes non-trusted devices, in which packets of information communicated across the network include network address information for a source device and a destination device of the packets of information are described herein. According to one embodiment, a process of establishing a more secure subnetwork includes inserting at least one credential into at least one packet of information issued by the source device, the credential assessable by a plurality of devices on the network, enabling transmission of the at least one packet of information from the source device to at least one destination device on the subnetwork, assessing the credential by at least one of the devices, and permitting the source device to communicate with the destination device conditioned upon the results of the assessing step. Other methods and apparatuses are also described.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of and claims priority to U.S. patent application Ser. No. 11/729,202, of the same title, filed Mar. 27, 2007, currently pending, which is a divisional of U.S. patent application Ser. No. 10/358,926, filed Feb. 4, 2003, which is abandoned, which is a continuation-in-part (CIP) of U.S. patent application Ser. No. 10/224,098, entitled “Establishing Authenticated Network Connections”, filed Aug. 19, 2002, now U.S. Pat. No. 7,069,438 issued Jun. 27, 2006, which applications/patents are fully incorporated in their entirety by this reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to providing network security to networks of any or arbitrary size. In particular, this invention relates to secure subnetworks within a general purpose network. 
       BACKGROUND OF THE INVENTION 
       [0003]    Most companies today have a strong network perimeter defense in place, and yet damaging attacks occur frequently. Many businesses extend their operations to the Internet, linking together their suppliers, customers, employees and partners. A Web-based front-end allows traditional back-end applications to be accessed from anywhere in the world. 
         [0004]    There is a well-understood need to protect the network perimeter and to implement access control between an Intranet and the Internet. IT (information technology) departments can choose from a large arsenal of tools, including ubiquitous firewalls, SSL (secure socket layer), and VPN (virtual private network) solutions. Strong encryption and authentication solutions can be deployed to protect sensitive information as it crosses public networks. However, once the network perimeter has been crossed, as shown in  FIG. 1A , the situation changes. Referring to  FIG. 1A , sensitive data is often unencrypted and sent from front end servers  601  to middle-tier servers  602  and back-end servers  603  in clear text. Back-end computers often lack adequate means of protecting themselves from network intrusions, and back-end applications are often completely oblivious to security needs. A cyber attacker or a disgruntled employee lurking on the corporate network can easily eavesdrop on the data or mount an attack against servers running critical applications. 
         [0005]    Protecting sensitive data and back-end servers inside enterprise networks is a difficult task. Many enterprises deploy legacy systems and applications that lack the means to protect themselves. While VPNs are effective for protecting data sent between isolated networks, they are virtually impossible or impractical to deploy inside existing enterprise Intranets without extensive rewiring, reconfiguration and major disruption of normal operations.  FIG. 1B  shows a typical example of using VPN to secure an existing network, where networks are partitioned into smaller networks connected by VPN tunnels  606  via VPN gateways  605 . However, these VPN gateways are expensive and require complex network reconfiguration, such as rerouting, of the existing network. These requirements often are not feasible to implement in an existing network having legacy applications running at the servers. 
       SUMMARY OF THE INVENTION 
       [0006]    Techniques used in a network that includes non-trusted devices, in which packets of information communicated across the network include network address information for a source device and a destination device of the packets of information are described herein. According to one embodiment, a process of establishing a more secure subnetwork includes inserting at least one credential into at least one packet of information issued by the source device, the credential assessable by a plurality of devices on the network, enabling transmission of the at least one packet of information from the source device to at least one destination device on the subnetwork, assessing the credential by at least one of the devices, and permitting the source device to communicate with the destination device conditioned upon the results of the assessing step. Other features of the present invention will be apparent from the accompanying drawings and from the detailed description which follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The present invention is illustrated by way of example and not limitation in the figures of the accompanying drawings in which like references indicate similar elements. 
           [0008]      FIG. 1A  illustrates a typical general purpose network; 
           [0009]      FIG. 1B  illustrates a typical general purpose network with VPN connections; 
           [0010]      FIG. 2  illustrates one embodiment of a secure subnetwork; 
           [0011]      FIG. 3A  illustrates a typical network connection separated by a firewall; 
           [0012]      FIG. 3B  illustrates one embodiment of a secure network tunnel (SNT); 
           [0013]      FIG. 4  illustrates one embodiment of a secure subnetwork; 
           [0014]      FIG. 5  illustrates one embodiment of a host having an SNT; 
           [0015]      FIG. 6  illustrates an alternative embodiment of a host having an SNT; 
           [0016]      FIG. 7  illustrates one embodiment of a process to establish an SNT; 
           [0017]      FIG. 8  illustrates one embodiment of an SNT; 
           [0018]      FIG. 9  illustrates a layout of a TCP option; 
           [0019]      FIG. 10  illustrates an exemplary layout of the TCP authentication option; 
           [0020]      FIG. 11  illustrates an alternative layout of the TCP authentication option; 
           [0021]      FIG. 12  illustrates a “man-in-the-middle” attack; 
           [0022]      FIG. 13  illustrates exemplary information flow during optional fully authenticated three-way TCP handshake; 
           [0023]      FIG. 14  illustrates an exemplary layout of the TCP authentication option data in the optional challenge phase; 
           [0024]      FIG. 15  illustrates an alternative layout of the TCP authentication option data in the optional challenge phase; 
           [0025]      FIG. 16  illustrates an exemplary layout of the TCP authentication option data in the optional response phase; 
           [0026]      FIG. 17  illustrates an alternative layout of the TCP authentication option data in the optional response phase; 
           [0027]      FIG. 18  illustrates an exemplary layout of the encrypted challenge data when hosts employ public key cryptographic methods; 
           [0028]      FIG. 19  shows an exemplary layout of the authentication data when the one-time password method is used for authentication; 
           [0029]      FIG. 20  illustrates an authentication process involving a trusted third party authority; 
           [0030]      FIG. 21  illustrates one embodiment of an authentication process for a network in which there are one or more intermediary communication nodes; and 
           [0031]      FIG. 22  illustrates an exemplary computer which may be used with one embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    The present invention will now be described in detail with reference to several embodiments thereof as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present invention. It will be apparent, however, to one skilled in the art, that embodiments may be practiced without some or all of these specific details. In other instances, well known process steps and/or structures have not been described in detail in order to not unnecessarily obscure the present invention. In other instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the present invention. The features and advantages of embodiments may be better understood with reference to the drawings and discussions that follow. 
         [0033]    Aspects, features and advantages of exemplary embodiments of the present invention will become better understood with regard to the following description in connection with the accompanying drawing(s). It should be apparent to those skilled in the art that the described embodiments of the present invention provided herein are illustrative only and not limiting, having been presented by way of example only. All features disclosed in this description may be replaced by alternative features serving the same or similar purpose, unless expressly stated otherwise. Therefore, numerous other embodiments of the modifications thereof are contemplated as falling within the scope of the present invention as defined herein and equivalents thereto. Hence, use of absolute and/or sequential terms, such as, for example, “will,” “will not,” “shall,” “shall not,” “must,” “must not,” “only,” “first,” “initially,” “next,” “subsequently,” “before,” “after,” “lastly,” and “finally,” are not meant to limit the scope of the present invention as the embodiments disclosed herein are merely exemplary. 
         [0034]    Accordingly, it is desirable to have a lightweight and easy-to-deploy method of creating secure subnetworks inside an existing general purpose network, such as, for example, an intranet or an Internet, without major reconfiguration of the network. Methods and apparatuses for creating secure subnetworks that allow a selection of a subset of hosts deployed on a network, enable protected communications among the hosts, and prevent eavesdropping and unauthorized accesses are described. The term “host” may refer either to a client computer or to a server computer coupled to a network, which may be computer system  800  shown in  FIG. 22 . According to one embodiment, an exemplary method creates secure encrypted pathways between and/or among the hosts. All network communications between hosts on the protected subnetworks are forwarded along the secure pathways. Each network connection, such as TCP/IP network connections, tunneled through the pathways can be authenticated before the connection is established. Embodiments of the invention are implemented in a kernel space of an operating system (OS) executing with the hosts, such that the protection is transparent to the applications running on the communicating hosts. Embodiments of the invention do not require installing additional hardware and additional network reconfiguration. As a result, embodiments of the invention allow server (e.g., TCP/IP server) concealment and protect a server from establishing unsanctioned connections from both local and remote networks. 
         [0035]    Some portions of the detailed descriptions which follow are presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of steps leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like. 
         [0036]    It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussion, it is appreciated that throughout the description, discussions utilizing terms such as “processing” or “computing” or “calculating” or “determining” or “displaying” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system&#39;s registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices. 
         [0037]    The present invention also relates to apparatus for performing the operations herein. This apparatus may be specially constructed for the required purposes, or it may comprise a general purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a computer readable storage medium, such as, but is not limited to, any type of disk including floppy disks, optical disks, CD-ROMs, and magnetic-optical disks, read-only memories (ROMs), random access memories (RAMs), EPROMs, EEPROMs, magnetic or optical cards, or any type of media suitable for storing electronic instructions, and each coupled to a computer system bus. 
         [0038]    The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatus to perform the required method steps. The required structure for a variety of these systems will appear from the description below. In addition, the present invention is not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the invention as described herein. 
         [0039]    A machine-readable medium includes any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computer). For example, a machine-readable medium includes read only memory (“ROM”); random access memory (“RAM”); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other form of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.); etc. 
       Overview 
       [0040]    According to one embodiment of the invention, secure network tunnel (SNT) technology creates secure tunnels between peers, also referred to as hosts, connected to unsecured networks. SNT may be based on publicly available technologies such as TLS (transport layer security) and IPSec (Internet protocol security), and/or other proprietary communication authentication schemes. SNT may reside in the TCP/IP (transport control protocol/Internet protocol) stack and allow existing applications to communicate through secure tunnels that may be dynamically established on demand. In one embodiment, no changes in the existing protocols and applications are needed to enable secure communication and no additional security gateway is required, as shown in  FIG. 2 , for example. 
         [0041]    Referring to  FIG. 2 , the exemplary system includes one or more front end servers  701 , middleware servers  702 , and enterprise backend servers  703  coupled to each other via one or more secure network tunnels  704 . In one embodiment, these servers (e.g., servers  701 ,  702 , and  703 ), as well as other servers, such as servers  707  to  708 , are enterprise servers within a general network, such as an Intranet or an Internet. As discussed above, without the technologies described herein, the connections between these servers are unsecured and unauthenticated connections, which are subject to a variety of attacks from externally (e.g., from Internet) or internally (e.g., within an Intranet). 
         [0042]    According to one embodiment, front end servers  701 , middleware servers  702 , and backend servers  703  are selected to form a subnetwork among a general network, such as an Intranet or an Extranet (e.g., an Internet), which may also include servers  707  to  708 . The subnetwork formed by front end servers  701 , middleware servers  702 , and backend servers  703  is established by connecting these servers through respective secure authenticated tunnels, such as secure tunnels  704 . Meanwhile, other connections, such as connections  705  and  706 , which connect other unselected servers (e.g., servers  707  and  708 ) may remain still unsecured and unauthenticated connections, which are subject to attacks externally or internally. In one embodiment, the subnetwork includes the entire general purpose network. 
         [0043]    In one embodiment, all data travelling between the servers within the secure subnetwork (e.g., servers  701  to  703 ) are transmitted via the respective secure and authenticated tunnels. As a result, communications among the servers within the secure subnetwork are protected. Such protected communications prevent eavesdropping and unauthorized accesses. 
         [0044]    According to yet another embodiment, each secure connection (e.g., a TCP/IP connection) through the secure tunnel may be authenticated before the connection is established, which will be described in details further below. Data transmitted through the respective secure tunnel connecting the peers may be encrypted according to an encryption algorithm. 
         [0045]    According to one embodiment, the secure tunnels may be established by a software program executed within a kernel space of the OS on all selected hosts within the protected subnetwork. As a result, all operations regarding encryption and authentication are transparent to the applications running in a user space. In one embodiment, the software program is embedded in a network driver associated with a network stack, such as the TCP/IP stack of the OS. In a particular embodiment, the software program may be distributed as part of a transport layer of the TCP/IP stack, such that its operations may be transparent to the applications. In addition, since the secure tunnels are implemented through a software program installed at all peers within the subnetwork, no additional hardware (e.g., VPN gateways) and no reconfiguration of the network (e.g., rerouting network traffic through the added VPN gateways) are needed. 
         [0046]    According to one embodiment, the SNT are established on demand dynamically. That is, peers establish on-demand secure tunnels when they need to communicate. For example, the original connection between a first peer (e.g., one of the front end servers  701 ) and a second peer (e.g., one of the middleware servers  702 ) is an unsecured and unauthenticated connection. When the first peer receives a request for accessing the second peer, the first peer establishes a secure network tunnel with the second peer in response to the request. The secure tunnel may be established statically prior to receiving a request for accessing a host. In one embodiment, the secure tunnels among the peers are established when the peers are in initialization stages (e.g., during booting of the peers). The secure tunnels may be established based on a policy, locally or enterprise wide, governing the connections among the peers. The secure tunnel may be authenticated prior to establishing the connection which is described in details further below. A security policy determines which peers participate in the secure subnetworks and which protocols are tunneled. Any attempt to communicate with a “secured” peer without establishing the protected tunnel may be denied by the software. Technology described herein uses a variety of authentication and encryption techniques and uses enterprise directory services to authenticate participating peers. In one embodiment, the SNT may be governed by an enterprise security policy. Alternatively, the SNT may be governed by a local security policy associated with the host. Furthermore, the enterprise and local security policies may coexist, such that, according to one embodiment, the local security policy may supercede the enterprise security policy. 
         [0047]    The SNT may be established using a secure communication protocol, such as SSL or IPSec, etc. The communicating peers involved in the subnetwork may be located on the same network. Alternatively, they may be located on different networks or different networks separated by a firewall. Furthermore, according to one embodiment, the tunneled communications may be performed over a TCP/IP protocol. Alternatively, the tunnel communications may be performed over a UDP, IP, or non-IP protocol. 
         [0048]    In one embodiment, an SNT deployment may simplify firewall configuration. With SNT deployed, all traffic between two peers can be tunneled though a single authenticated and encrypted connection and thus the technologies described herein can potentially reduce the number of open ports on a firewall.  FIG. 3A  is a block diagram of a typical firewall configuration without an SNT deployed. As shown in  FIG. 3A , peers  751  and  752  are separated by a firewall  753 . In order to allow certain protocols, such as SMTP (simple mail transport protocol), FTP (file transport protocol), Telnet, and HTTP (hypertext transfer protocol), to pass through firewall  753 , firewall  753  has to open an individual port to accommodate each protocol it supports. However, with the technologies described herein deployed as shown in  FIG. 3B , according to one embodiment, the secure tunnel may only open one port to allow one protocol (e.g., TCP protocol) and force all network traffic through the single port and single tunnel. As a result, security has been greatly improved. 
         [0049]      FIG. 4  shows a typical Enterprise Security System (“ESS”) deployment comprised of two security domains: Internet domain  501  and Intranet domain  502 . In Internet domain  501  external users  507  are authenticated and authorized to traverse firewall  506  and to use applications in Web tier  503  by a customer directory service  510 . A directory service provides a place to store information about network-based entities, such as applications, files, printers, and people. The directory service provides a consistent way to name, describe, locate, access, manage, and secure information about these individual resources. Further, a directory service acts as the main switchboard of the network operating system. The directory service is the central authority that manages the identities and brokers the relationships between these distributed resources, enabling them to work together. Because a directory service supplies these fundamental network operating system functions, the directory service must be tightly coupled with the management and security mechanisms of the operating system to ensure the integrity and privacy of the network. The directory service also plays a critical role in an organization&#39;s ability to define and maintain the network infrastructure, perform system administration, and control the overall user experience of a company&#39;s information systems. In one embodiment, the network connections may be wireless network connections. 
         [0050]    When external user  507  logs into a web application  508 , user  507  is authenticated  509  against the customer directory service  510  and her request is allowed to proceed to the applications located in middle tier  504  and at enterprise backend server  505 . 
         [0051]    Referring to  FIG. 4 , in Intranet domain  502 , internal users  511  are authenticated and authorized to access applications in middle tier  504  and at enterprise backend  505  by internal enterprise directory service  513 . When an internal user  511  wishes to use applications in middle tier  504  or at enterprise backend  505  his credentials are passed  512  by the security-aware applications to enterprise directory  513 , which authenticates and authorizes internal user  511 . 
         [0052]    As shown in  FIG. 4 , in Web tier  503 , it is a common practice to authenticate and authorize users  507 . However, in a drastic departure from common security principles, in middle tier  504  and at enterprise backend  505 , communications are often unauthenticated and unauthorized. This deficiency usually results from the absence of security features built into the legacy mission critical applications deployed at enterprise backend  505  and in middleware applications, such as CORBA (common object request broker architecture) services, located in middle tier  504 . Security weaknesses in the applications deployed in middle tier  504  and at enterprise backend  505  could be easily exploited by malicious external  507  or internal  511  users who may break into mission critical applications or eavesdrop on unprotected communications  514 . 
         [0053]      FIG. 5  depicts a block diagram illustrating how an embodiment of SNT module deployed in operating system (OS) Kernel  528  establishes authorizations for network connections for secure tunnel  521  and for tunneled connections  522 , employing information from enterprise directory  513 . The operating system used in the host may be a Windows operating system from Microsoft Corporation. Alternatively, the operating system may be a Mac OS from Apple Computer, Inc. Furthermore, the operating system may be a Linux, Unix, or VAX/VMS operating system. Other operating systems such as, for example, a real-time operating system or an embedded operating system, may be utilized. 
         [0054]    During establishment of authenticated secure tunnel  521  or authenticated tunneled connection  522 , a connection request carrying a credential  532  reaches server computer  534 . SNT network manager module  523  deployed in operating system IP Stack  533  extracts credential  532  and passes it to the SNT authentication and authorization manager (“A 2  Manager”) module  524  via an internal programmatic interface. 
         [0055]    In one embodiment, a management module such as SNT A 2  Manager  524 , who wishes to authenticate and authorize a network connection, communicates with enterprise directory  513  via SNT authentication and authorization daemon (“A 2  Daemon”)  526  deployed in application space  535  of server computer  534 . The communication between SNT A 2  Manager  524  and A 2  Daemon  526  occurs over an OS level communications mechanism  527  such as, but not limited to, a shared memory segment, memory mapped file, etc. A 2  Daemon  526  picks up the request and forwards it to enterprise directory  513  through a dedicated enterprise security system adapter (“ESS Adapter”)  529 . ESS Adapter  529  translates the authentication request of A 2  Daemon  526  into the format and protocol  530  understood by enterprise directory  513 . Examples of the protocols supported by ESS Adapter  529  used to communicate with enterprise directory  513  include, but are not limited to, LDAP (Lightweight Directory Access Protocol), Active Directory from Microsoft Corporation, OS/390 SAF/RACF/ACF2/Top Secret, etc. Other protocols apparent to those with ordinary skills in the art may be utilized. 
         [0056]    Further referring to  FIG. 5 , upon receiving a response from enterprise directory  513 , ESS Adaptor  529  translates it into internal SNT A 2  Daemon  526  format. A 2  Daemon  526  then passes the authorization response to A 2  Manager  524  via OS level communications mechanism  527 . 
         [0057]    Depending on enterprise directory  513  responses, A 2  Manager  524  makes a decision as to whether to allow establishment of a secure tunnel  521 , or to allow a network connection  536  to Application  531 , or to deny network communications request  522 . A 2  Manager  524  may make its decision to allow or to deny the communications request based on a local policy optionally superimposed on a policy provided by enterprise directory  513 . For example, enterprise wide system administrator may set up an enterprise policy, which may be included in an enterprise directory service (e.g., enterprise directory  513  of  FIG. 4 ), that all hosts involved in the secure subnetwork may only accept certain protocols, such as SMTP, FTP, Telnet, and HTTP, because the hosts are serving as servers specifically for those protocols. However, an individual host or server may only operate for a specific function, such as a mail server. As a result, a local administrator may set up a local policy, which may be included in a local customer directory service (e.g., customer directory  510  of  FIG. 4 ), to limit the respective server to only accept SMTP protocol. As a result, security of an individual host has been further improved. 
         [0058]    In the case of a positive enterprise directory  513  response, the A 2  Manager optionally adds a record about a newly established network connection  522  to SNT authentication and authorization cache (“A 2  Cache”)  525 . A 2  Manager  524  may support arbitrary authorization models including, but not limited to, RBAC (role based access control) or DAC (discretionary access control). Other models apparent to those of ordinary skill in the art may be utilized. 
         [0059]    According to one embodiment, A 2  Cache  525  is policy-driven and it allows the retention of temporary authentication and authorization information about established connections. The connection information is stored in the A 2  Cache for a limited time or a maximal number of accesses, as determined by a local policy. Once the policy limits are exceeded, the corresponding cache entry is flushed and Enterprise Directory  513  again is accessed to authorize the next peer&#39;s communication request  522 . Being local to A 2  Manager  524 , A 2  Cache  525  significantly reduces the time required to receive authentication and authorization information without endangering communications security. 
         [0060]      FIG. 6  is a block diagram of an alternative embodiment illustrating how ESS Adapter  529  is deployed in OS Kernel  528 , and SNT A 2  Manager  524  communicates with ESS Adapter  529  directly rather than through an intermediary. ESS Adapter  529  communicates with Enterprise Directory  513  in the same fashion as described above. 
         [0061]    SNT technology offers a wide variety of network connection authentication and protection capability. In one embodiment all requests for TCP/IP network connections between the communicating peers are authenticated before connection is permitted, which will be described in details further below. 
         [0062]      FIG. 7  is a block diagram illustrating an embodiment of a process for establishing a mutually authenticated TCP/IP connection, which may be used to establish an SNT tunnel. According to one embodiment, connection initiator  551  sends a TCP/IP connection request SYN packet  553  to connection acceptor  552 . SYN packet  553  contains connection initiator&#39;s  551  identity and encrypted authentication information  556 , which identifies connection initiator  551 . It also contains the connector initiator&#39;s challenge value for connection acceptor  552 . 
         [0063]    Connection acceptor  552  communicates with enterprise directory  513  to authenticate connection initiator  551  using her identity and authentication information  556  found in SYN packet  553 . If authentication is successful, connection acceptor  552  decrypts connection initiator&#39;s  551  challenge. Connection acceptor  552  then transforms it, adds its own challenge and encrypts both values. Connection acceptor  552  then passes authentication payload  557  to connection initiator  551  in TCP/IP SYN/ACK packet  554 . Connection initiator  551  decrypts its own transformed challenge value and after making sure that it is correct, transforms and encrypts connection acceptor&#39;s  552  challenge value and passes it back to connection acceptor  552  in TCP/IP ACK packet  555 . Connection acceptor  552  decrypts and verifies connection initiator&#39;s  551  response  558  and hands off the newly established connection to destination application  560 . It will be appreciated that pre-connection authentication may be applied to the establishment of tunneled network connections and to the establishment of the secure tunnel, itself. 
         [0064]    In an alternative embodiment, referring to  FIG. 7 , network connections established between communicating peers are authenticated unidirectionally. For example, connection initiator  551  authenticates to connection acceptor  552 , or is not authenticated at all. In this embodiment, security of connection is achieved through the properties of the secure tunnel. 
         [0065]      FIG. 8  is a block diagram illustrating an embodiment of an SNT. According to one embodiment, an exemplary secure tunnel  521  is established between SNT modules  573  and  574  which are deployed in IP stacks  575  and  576  of communicating Server A  571  and Server B  572 . In this embodiment, secure tunnel  521  was requested by SNT module  573  on behalf of potentially security-unaware application  577 , which requested a communication with an SNT-protected service  578 . SNT module  574 , which is deployed in IP Stack  576  of server  572  and hosts desired service  578 , accepted secure tunnel  521 . 
         [0066]    Initiating SNT module  573  and accepting SNT module  574  establish a secure tunnel  521  depending on the security policy set forth at an enterprise directory. Initiating SNT module  573  may optionally superimpose its own non-contradictory local policies such as, but not limited to, allowing only certain accounts on server  571  to establish tunneled connections  522  to server  572 . 
         [0067]    Secure tunnel  521  can be established by using the SSL/TLS protocol or a variant of it such as WTLS (wireless transport layer security), the IPSec protocol or other communications protocols, which support encrypted communications. Initiating SNT module  573  and accepting SNT module  574  may negotiate a protocol for secure tunnel  521  using the EAP (extensible authentication protocol). Other protocols may be utilized. 
         [0068]    During establishment of secure tunnel  521 , initiating SNT module  573  and accepting SNT module  574  unidirectionally or mutually authenticate each other via enterprise directory  513 . Secure tunnel  521  can be negotiated by the communicating parties without any authentication using, for example, but not limited to, a Diffie-Hellman key agreement method. Secure tunnel  521  can also be established as requiring only message integrity verification and without the privacy property. Application  577  and service  578  can be communicating through secure tunnel  521  using, for example, TCP/IP protocol, UDP protocol, or any other protocols, such as non-IP based network protocols. 
         [0069]    According to one embodiment, secure tunnel  521  may be established dynamically on demand. For example, when SNT module  573  receives a request from application  577  to access service  578  located on server  572 , SNT module  573  may check whether secure tunnel  521  has been previously established. If SNT  521  has not been established, SNT module  573  may try to establish an SNT with SNT module  574  of server  572 . In one embodiment, SNT modules  573  and  574  may mutually authenticate with each other prior to establishing the connection. In addition, SNT modules  573  and  574  may inspect the request originating from application  577  to determine whether such request should be entitled for service  578  via enterprise directory  513 . Once SNT tunnel  521  has been established, SNT module  573  may encrypt data received from application  577  and transmit the data to server  572  via SNT  521 . It is appreciated that all operations performed by SNT module  573  are performed in a kernel space of the OS executed within server  571 , such that the operations are transparent to application  577 . In one embodiment, application  577  may be a security-unaware application (e.g., a legacy application). However, the data exchanged between servers  571  and  572  are transmitted via SNT tunnel  521  which are not feasible to attack by an intruder. 
         [0070]    According to one embodiment, when SNT module  574  receives an encrypted data from SNT module  573 , SNT module  574  may inspect the encrypted data to determine whether such data has been transmitted from a trusted peer via a secure tunnel. The inspection may be performed against enterprise directory  513  services. Note that server  572 , which has an SNT with server  571 , may also have other connections (e.g., unsecured connections) with other hosts (e.g., non-members of the subnetwork). Once SNT module  574  determines that the data is received from SNT module  573 , it decrypts the encrypted data according to an agreed upon encryption/decryption algorithm which may be stored in enterprise directory  513 . Thereafter, SNT module  574  transmits the decrypted data to the designated application  578 , which may be a security unaware application. It is appreciated that all operations performed by SNT module  574  are performed in a kernel space of the OS executed within server  572 , such that the operations are transparent to application  578 . 
         [0071]    Note that SNT modules  573  and  574  are software programs, which may be installed on all hosts constituting the secure subnetwork within a general purpose network, such as an Intranet. The software package including SNT modules  573  and  574  may be distributed and installed by an enterprise wide system administrator. The software package may be installed in addition to an existing network stack of an operating system. That is, when the software package is installed, it “hooks” on the network stack, such as TCP/IP stack, such that the SNT modules may intercept the network traffic (e.g., outgoing and incoming traffics) within the network stack. Then the SNT modules may perform any necessary operations including, but not limited to, authenticating the request against a directory service, establishing an SNT tunnel with a destination host if it has not been established, encrypting outgoing packets, and decrypting incoming packets, etc. In one embodiment, such operations are completely transparent to the respective applications and do not require any changes at the application level. In one embodiment, the software package may be uninstalled and the original network stack may be restored without the knowledge of the respective applications. Other configurations may be utilized. 
       Establishment of Authenticated Network Connections 
       [0072]      FIG. 9  is an exemplary layout of a TCP option field within a TCP header in accordance with the TCP/IP protocol, which may be used in SYN packet  553 , SYN/ACK packet  554 , and ACK packet  555  of  FIG. 7 , to establish an authenticated connection prior to establishing a connection with a host. TCP option  261  consists of option type octet  121 , option length octet  122 , and option data  123 . In one embodiment, TCP option  261  is padded to a multiple of 4 octets by a “No Operation” TCP option. 
         [0073]    In order to selectively prevent the establishment of unauthorized TCP/IP connections, novel measures are taken.  FIG. 10  illustrates a single instance of a special TCP option  261 , OPTION_A  301 , that is added to SYN packet  553 . In one embodiment, OPTION_A  301  is comprised of an octet which contains the option A ID  203 ; an octet containing option length  204 ; and followed immediately by four octets containing peer Id  205  of a client computer at a server computer site. The octet following peer ID  205  contains a unique identifier of the authentication method, auth method ID  206 , which is used to authenticate the client computer. 
         [0074]    Octets following auth method ID  206  contain authentication data, auth data  207 . In one embodiment, auth data  207  length is limited to approximately 23 octets due to the size limitation of the TCP header. 
         [0075]    In another embodiment, as illustrated on  FIG. 11 , a single instance of a special TCP option  261 , OPTION_B  303 , is added to SYN packet  553 . In one embodiment, OPTION_B  303  is comprised of an octet that contains the option B ID  302  and option length  208  octet set to zero, indicating that length of the following TCP option  261  data is 0. 
         [0076]    When OPTION_B  303  is used, authentication information is placed in the data portion of SYN packet  553 . Authentication information begins with a single octet auth info length  209  containing total length of the peer ID  210 , auth method ID  211  and auth data  207  fields. This octet is followed immediately by eight octets containing peer ID  210  for the client computer at the site of server computer. The following octet, auth method ID  211 , contains a unique identifier of the authentication method used to authenticate the client computer by the server computer. Octets following auth method ID  211  contain authentication data in auth data  207 . In one embodiment, auth data  207  length is limited to approximately 128 octets due to the data size limitation of the TCP/IP packet. 
         [0077]    Sending a SYN packet to a TCP/IP server is not the only method to discover a network service. Activity in which a party tries to locate services available on a network is called “scanning”. Typically, scanning is performed by sending SYN packets to the ports of the hosts deployed on the network. This type of scanning is called “SYN-scan”. 
         [0078]    In addition to SYN-scan, a sophisticated attacker can utilize FIN, ACK or NULL scans. These scans send an unsolicited packet with the respective TCP flag set, as denoted by the name of the scan. Packets sent during these scans are not a part of any valid established TCP connection. The TCP/IP protocol requires the host that receives one of those packets to generate a response, an RST packet, if the TCP port was closed, and to ignore the packet if the TCP port was open. This behavior, prescribed by the TCP/IP protocol standard, allows the attacker to determine which TCP ports are open on a target Host. 
         [0079]    In order to prevent open TCP port detection by FIN, ACK or NULL scans, in one embodiment, the server computer tracks all established TCP connections. The host computer generates an RST Packet in response to any packet sent to an open TCP port that does not belong to a valid TCP connection. Providing the same response to packets sent to an open TCP port and to a closed TCP port denies an attacker any useful information. 
         [0080]    Before attempting the establishment of an authenticated TCP/IP connection, the client computer and the server computer agree on the type of authentication method that they will use for authentication purposes. Various embodiments include, but are not limited to, the following authentication methods:
       cryptographic hashed message authentication code (HMAC);   cryptographic hash with timestamp;   one time password;   public key cryptography-based;   based on security assertion provided by a trusted third party.       
 
         [0086]    Each of these authentication methods includes a variation that introduces additional authentication steps designed to prevent the “man-in-the-middle” (MITM) attacks against the protected server computer. 
         [0087]    As illustrated in  FIG. 12 , a powerful adversary  213  may position itself on the network on the route of TCP/IP connection initiation, and modify SYN packet  200  sent by client computer  100  to server computer  101 . Adversary  213  is capable of changing the original source address  381  field value in the IP header  380  of SYN packet  200  to the adversary&#39;s IP address. 
         [0088]    As a consequence of such action by adversary  213 , upon receiving the amended SYN* packet  217 , server computer  101  verifies authentication data in the amended SYN* packet  217  if that authentication data did not include a cryptographically protected reference to the IP address of client computer  100 . Given the fact that in a large number of deployments, the source IP address cannot be verified due to the widespread use of Network Address Translation (NAT) technology by network perimeter devices, an MITM (man in the middle) attack could be successfully staged by adversary  213 . 
         [0089]    A successful MITM attack against server computer  101  forces it to send a response SYN*/ACK packet  218  to adversary  213  instead of to client computer  100 . As a result, server computer&#39;s TCP/IP session is diverted to adversary  213 . 
         [0090]    Special variations of the authentication methods include provision for a challenge response exchange between client computer  100  and server computer  101  to further verify the source of the nascent TCP/IP session prior to the establishment of any connection. As illustrated in  FIG. 13 , upon receiving the SYN packet  200  with authentication information  219 , server computer  101  uses a shared secret key or a public key of the client computer  100  to encrypt a randomly generated octet sequence, i.e. the challenge. Server computer  101  places the challenge in the response SYN/ACK packet  201  and sends it to client computer  100 . Upon receiving the SYN/ACK packet  201 , client computer  100  decrypts the challenge using the shared secret key or a private key, transforms it according to an established algorithm, and encrypts it with the shared secret key or with the public key of server computer  101 . Next, client computer  100  sends an encrypted transformed challenge back to server computer  101  in the ACK packet  202  with encrypted transformed server challenge  221 . Upon receiving ACK packet  202  with encrypted transformed server challenge  221 , server computer  101  decrypts the transformed challenge and verifies that client computer  100  transformed the challenge correctly. 
         [0091]      FIG. 14  shows one embodiment of the challenge data layout in the SYN/ACK packet  201  sent by server computer  101  to client computer  100 . A single instance of a special TCP option  261 , OPTION_A  301 , is added to SYN/ACK packet  201 . In one embodiment, OPTION_A  301  is comprised of an octet that contains option A ID  203 , followed by an octet indicating the length of the following TCP/IP option  261  data, option length  204 . Encrypted challenge information, encrypted challenge data  224 , immediately follows option length  204 . The length of encrypted challenge data  224  depends on the type of authentication algorithm in use. In one embodiment, authentication data length is limited to approximately 27 octets due to the size limitation of the TCP header. 
         [0092]    In another embodiment, as illustrated on  FIG. 15 , a single instance of a special TCP option  261 , OPTION_B  303 , is added to SYN/ACK packet  201  sent by server computer  101  to client computer  100 . In one embodiment, OPTION_B  303  is comprised of an octet that contains option B ID  302 , followed by a zero octet, option length  208 , which indicates that length of the following TCP/IP option  261  data is 0. When OPTION_B  303  is used, encrypted challenge information is placed in the data portion of SYN/ACK packet  201 . 
         [0093]    Encrypted challenge information begins with a single octet, challenge info length  227 , containing the length of the following encrypted challenge information. Octets following challenge info length  227  contain encrypted challenge data  224 . In one embodiment, challenge data length is limited to approximately 128 octets due to the size limitation of the TCP/IP packet data size. 
         [0094]      FIG. 16  shows one embodiment of the response data layout in the ACK packet  202  sent by client computer  100  to server computer  101 . A single instance of a special TCP option  261 , OPTION_A  301 , is added to ACK packet  202 . In one embodiment, OPTION_A  301  is comprised of an octet that contains the option A ID  203 , followed by an octet indicating the length of the following TCP/IP option  261  data, option length  204 . Encrypted response information, encrypted response data  231 , immediately follows option length  204 . The length of encrypted response data  231  depends on the type of authentication algorithm in use. In one embodiment, authentication data length is limited to approximately 27 octets due to the size limitation of the TCP header. 
         [0095]    In another embodiment, as illustrated on  FIG. 17 , a single instance of a special TCP option  261 , OPTION_B  303 , is added to ACK packet  202  sent by client computer  100  to server computer  101 . In one embodiment, OPTION_B  303  is comprised of an octet that contains option B ID  302 , followed by a zero octet, option length  208 , which indicates that length of the following TCP/IP option  261  data is 0. When OPTION_B  303  is used, encrypted response information is placed in the data portion of ACK packet  202 . 
         [0096]    Encrypted response information begins with a single octet, response info length  234 , containing the length of the following encrypted response information. Octets following response info length  234  contain encrypted response data  231 . In one embodiment, challenge data length is limited to approximately 128 octets due to the size limitation of the TCP/IP packet data size. 
         [0097]    When hosts use a secret key-based authentication method, server computer  101  generates an 8 octet long random value, Salt, concatenates it with a shared secret key value, Secret, and with the sequence number field, Seq#, from the TCP header in SYN packet  200  sent by client computer  100 . Server computer  101  applies a secure hash cryptographic algorithm (e.g., MD5, SHA-1, etc.) to the resulting octet sequence, thus generating a challenge value, Ch: 
         [0000]        Ch=H (Salt|Secret|Seq#) 
         [0098]    Then server computer  101  concatenates the Salt value and the challenge value, Salt|Ch, and places the result in encrypted challenge data  224  field of SYN/ACK packet  201 . 
         [0099]    Upon receiving the challenge, client computer  100  verifies that the challenge value, Ch, was indeed sent by server computer  101  by locally recalculating that value. In order to create a response, client computer  100  concatenates the received challenge value, Ch, with the shared secret value, Secret, and computes a secure cryptographic hash of the result, e.g. MD5 or SHA-1: 
         [0000]        H ( Ch |Secret) 
         [0100]    Client computer  100  places the computed response value in encrypted response data  231  field of the ACK packet  202 . Upon receiving ACK packet  202 , server computer  101  verifies the response value computed by the client computer  100 . 
         [0101]    Server computer  101  selects a secure cryptographic hash algorithm according to its local policy. Client computer  100  determines the type of secure cryptographic hash algorithm used by server computer  101  from the value found in the option length  204  field if OPTION_A  301  layout is used (e.g., 16 octets for MD5, 20 octets for SHA-1). If OPTION_B  303  layout is used, then client computer  100  determines the secure cryptographic hash algorithm used by server computer  101  from the value found in the challenge info length  227  field (e.g., 16 octets for MD5, 20 octets for SHA-1). To calculate the response value, client computer  100  must use the same secure cryptographic hash algorithm as is used by server computer  101  when it calculates the challenge value. 
         [0102]    When hosts employ public key cryptography-based authentication methods, server computer  101  generates a 12 octet-long random value, Rand, concatenates it with the sequence number field, Seq#, from TCP header  113  in the SYN packet  200  sent by client computer  100 , Ch=Rand|Seq#, and encrypts it with server computer  101  private key, Pr v S : 
         [0000]        E   Prv     S   ( Ch ) 
         [0103]    Server computer  101  places the result in encrypted challenge data  224  of SYN/ACK packet  201 . 
         [0104]    Upon receiving the challenge, client computer  100  decrypts the challenge value using server computer  101  public key, Pub S : 
         [0000]        Ch=D   Pub     S   ( E   Prv     S   ( Ch )) 
         [0105]    Client computer  100  verifies that the challenge, Ch, was indeed computed by server computer  101  by comparing the value of the Seq# with the sequence number value found in sequence number field as sent by client computer  100  to server computer  101  in SYN packet  200 . 
         [0106]    After verifying the origin of the challenge value, client computer  100  encrypts the received challenge value, Ch, with client computer  100  private key, Pr v C : 
         [0000]        E   Prv     C   ( Ch ) 
         [0107]    Client computer  100  places the computed response value in encrypted response data  231  field of ACK packet  202 . 
         [0108]    Upon receiving ACK packet  202 , server computer  101  decrypts the value in encrypted response data  231  field of ACK packet  202  using client computer  100  public key, Pub C : 
         [0000]        Ch=D   Pub     C   ( E   Prv     C   ( Ch )) 
         [0109]    Server computer  101  verifies client computer  100  response by comparing the decrypted Rand value with the random value which it sent to client computer  100  in SYN/ACK packet  201 . 
         [0110]      FIG. 18  illustrates the structure of encrypted challenge data  224  field. The public key alg ID  240  octet contains a numeric identifier of a public key cryptographic algorithm used to encrypt challenge data in encrypted data  241  field that follows. The choice of public key cryptographic algorithm depends on server computer&#39;s  101  policy. In one embodiment, server computer  101  can choose, without limitation, to use original (e.g., RSA) or ECC (Elliptic Curve Cryptography) based versions of public key encryption algorithms. In one embodiment, hosts follow the PKCS#1 (Public Key Cryptography Standards #1) guidelines when performing original RSA public key encryption. The hosts follow the ANSI X9.62 ECDSA (Elliptic Curve Digital Signature Algorithm) guidelines for the ECC variants of the public key encryption. 
         [0111]    As described above, SYN packet  200  contains cryptographically secured data that authenticates client computer  100  to server computer  101 . Following are descriptions of various embodiments that are meant to be illustrative, which do not exclude other embodiments of this invention. 
         [0112]    Hashed Message Authentication Code (HMAC) is an authentication method that may be used to authenticate client computer  100  to server computer  101 . HMAC of SYN packet  200  is computed by concatenating the shared secret key, Secret, with values found in the following fields: source IP address, SrcIPAddr, destination IP address, DestIPAddr, source port number, SrcIPort#, Destination Port Number, DestPort#. In one embodiment, the HMAC computation is performed according to the guidelines found in the IETF RFC 2104 “HMAC: Keyed Hashing For Message Authentication” document (“RFC2104”): 
         [0000]      HMAC(SrcIPAddr|DestIPAddr|SrcIPPort|DestIPPort|Secret) 
         [0113]    Server computer  101  verifies the HMAC using data in SYN packet  200  sent by client computer  100 . 
         [0114]    In another preferred embodiment, a different authentication method may be used to authenticate client computer  100  to server computer  101 , which is based on a timestamp provided by a trusted third party such as a NTP (Network Time Protocol) server. Client computer  100  concatenates a decimal ASCII value of the NTP timestamp, T C , with the shared secret key, Secret, and, in one embodiment, computes a cryptographic hash value according to the guidelines found in the RFC2104: 
         [0000]        H =HMAC( T   C |Secret) 
         [0115]    Client computer  100  concatenates the timestamp, T C , with the HMAC value, H, T C |H, and sends it to server computer  101 . 
         [0116]    Upon receiving SYN packet  200  from client computer  100 , server computer  101  verifies the HMAC value and, if successful, obtains a NTP timestamp, T S , from a trusted server. Server computer  101  compares the trusted timestamp value, T S , with the timestamp value received from client computer  100 , T C , and if the value of the timestamp value received from client computer  100 , T C , is within the window allowed by server computer  101  policy, Δ, |T C −T S |≦Δ, server  101  computer accepts the communications session. 
         [0117]    In yet another preferred embodiment, the authentication method used to authenticate client computer  100  to server computer  101  is based on one-time password technology. Prior to establishing the first authenticated TCP/IP session, client computer  100  and server computer  101  agree on a pair of publicly known non-zero values, Salt 0 , and TrfCount 0  (where TrfCount 0 &lt;256). Client computer  100  and server computer  101  also use another publicly known value, SeqCnt, which initially is set to zero. 
         [0118]    In order to compute the next one-time password value, both client computer  100  and server computer  101  concatenate the Salt 0  value and the shared secret key, Secret, and computes its HMAC TrfCount 0  times: 
         [0000]      OTP 0 =HMAC TrfCount     0   (Salt 0 |Secret) 
         [0119]    To calculate the next one-time password value, OTP 1 , both client computer  100  and server computer  101  subtract one from the TrfCount 0  value. If TrfCount 0 −1=0, the host (client computer  100  or server computer  101 ) calculates Salt 1  value as: 
         [0000]      Salt 1 =HMAC(Salt 0 |Secret) 
         [0120]    The host also computes the next maximal transformation counter value, TrfCount 1 , as: 
         [0000]      TrfCount 1 =HMAC(Salt 1 |Secret) mod 256    
         [0121]    If TrfCount 1 =0, the HMAC is calculated again: 
         [0000]      TrfCount 1 =HMAC(HMAC(Salt 1 |Secret)) mod 256    
         [0122]    This calculation continues until a non-zero value for TrfCount 1  is obtained. Once a new value of the maximal transformation counter is computed, the host (client computer  100  or server computer  101 ) increments the SeqCnt value by one. 
         [0123]    In order to thwart replay attacks, the host (client computer  100  or server computer  101 ) which verifies a one-time password value ensures that the sequence counter value, SeqCnt C , submitted by the claimant is greater or equal to the locally known sequence counter value, SeqCnt V , and that the transformation counter value, TrfCount C , submitted by the claimant is less or equal than the locally known transformation counter value, TrfCount V : 
         [0000]      SeqCnt C ≧SeqCnt V  and TrfCount C ≦TrfCount V  
 
         [0124]      FIG. 19  shows an exemplary layout of auth data  207  field when the one-time password authentication method is used. Client computer  100  places its computed one-time password value, OTP n , in the one-time password  372  field, the SeqCnt i  value into the sequence counter field and the TrfCount i  value in the transform counter field. 
         [0125]    In still another embodiment, the authentication method used to authenticate client computer  100  to server computer  101  is based on public key cryptographic methods. In one embodiment, client computer  100  encrypts the sequence number field, Seq#, from the TCP header in SYN packet  200  which it is preparing for transmission to server computer  101 , with client computer  100  private key, Pr v C : 
         [0000]        E   Prv     C   (Seq#) 
         [0126]    Upon receiving SYN packet  200  from client computer  100 , server computer  101  decrypts the Seq# value using client computer  100  public key, Pub C : 
         [0000]      Seq#= D   Pub     C   ( E   Prv     C   (Seq#)) 
         [0127]    Server computer  101  verifies that the sequence number, Seq#, contained in auth data  207  field is the same as the sequence number value found in the sequence number field of SYN packet  200  sent by client computer  100  to server computer  101 . 
         [0128]      FIG. 20  illustrates another embodiment in which the authentication method used to authenticate client computer  100  to server computer  101  is based on the presence of a trusted security assertion provider. In one embodiment, server computer  101  and client computer  100  establish a trust relationship with a security assertion provider  401  entity. This trust relationship is established via some out-of-the-band methods OOBM C    410  and OOBM S    411 . 
         [0129]    When client computer  100  wishes to establish a new TCP/IP communications session with server computer  101 , it sends to security assertion provider  401  a credential request  402  to ask for the issuance of an authentication credential. Security assertion provider  401  issues client computer  100  an authentication credential such as, without limitation, an authentication token, a digital certificate or a Kerberos ticket. Security assertion provider  401  forwards this issued credential  403  to client computer  100 . 
         [0130]    Upon receiving credential  403  from security assertion provider  401 , client computer  100  embeds the credential  403  in SYN packet  200  and sends this packet to server computer  101 . 
         [0131]    When server computer  101  receives SYN packet  200 , it extracts credential  403 . Depending on the type of credential  403 , server computer  101  verifies it, without limitation, locally, with security assertion provider  401  or any other trustworthy entity capable of verifying credential  403 . 
         [0132]    Password-based authentication may be used in one embodiment as the authentication method used to authenticate client computer  100  to server computer  101 . Client computer  100  incorporates a password in SYN packet  200 . 
         [0133]    Upon receiving SYN packet  200  sent by client computer  100 , server computer  101  compares the received password value with a locally stored value and accepts the connection if password values match. 
         [0134]      FIG. 21  illustrates another embodiment in which the authentication method used to authenticate client computer  100  to server computer  101  is based on the presence of one or more intermediary communication nodes, relay devices  421 - 422 , each of which relays authenticated packets  420  sent between client computer  100  and server computer  101 . 
         [0135]    In this embodiment, an authenticated packet  420 , P 1 , sent by client computer  100 , is authenticated for acceptance by the next relay device  421 . After authenticating the packet relay device  421  modifies or replaces authentication information in the packet with its own authentication information and forwards this modified authentication packet, P 2 , to the next relay device  422 , etc. Finally, authenticated packet  420 , P n , (a packet whose authentification information has been modified n−1 times before the packet reaches server computer  101 ) reaches server computer  101 . 
         [0136]    Upon receiving and verifying authentication information in authenticated packet  420 , P n , server computer  101  transmits the acceptance packet through the same or an alternative chain of relay devices  421 - 422 . 
         [0137]    Client computer  100  and/or server computer  101  may be any kind of computer, wireless devices, personal digital assistants (PDAs), laptop computers, phones or other communication devices or combinations thereof. 
         [0138]    Furthermore, in one embodiment, client computer  100  is authenticated against a database of hosts stored in a computer readable memory. In such a case, peers being authenticated may have been registered before connection establishment was attempted. This memory may be part of server computer  101  or accessible thereby. In one embodiment, the authentication technique described herein is integrated with enterprise security systems, such as, for example, RADIUS (Remote Authentication Dial-In User Service), Windows Domain, etc., to determine valid peers. 
         [0139]    In one embodiment, such a process in which authentication of registered peers may be performed includes accessing a memory storing a list of one or more valid peers, comparing the prospective peer with the list of one or more potentially valid peers and the data used to authenticate them to determine if the prospective peer is in the list, and authenticating the prospective peer if determined to be on the list. The data used to identify the peer is in the SYN packet. After a particular peer is determined to be valid, a server, such as server  101  described above, may use other information, such as, for example, the encrypted information or other forms of information described above in the SYN packet, to determine whether the prospective peer is who they say they are. 
         [0140]      FIG. 22  shows a block diagram of an exemplary computer which may be used with an embodiment of the invention. For example, system  800  shown in  FIG. 22  may used as hosts to form a secure subnetwork within a general purpose network, such as front end servers  701 , middleware servers  702 , or backend servers  703  of  FIG. 2 . Note that while  FIG. 22  illustrates various components of a computer system, it is not intended to represent any particular architecture or manner of interconnecting the components, as such details are not germane to the embodiments of the present invention. It will also be appreciated that network computers, handheld computers, cell phones, and other data processing systems which have fewer components or perhaps more components may also be used with the embodiments of the present invention. Further detailed information with respect to establishments of an authenticated network connection can be found in the co-pending application Ser. No. 10/224,098, entitled “Establishing Authenticated Network Connection”, filed Aug. 19, 2002, now U.S. Pat. No. 7,069,438, which is hereby expressly incorporated by reference. 
         [0141]    As shown in  FIG. 22 , the computer system  800 , which is a form of a data processing system, includes a bus  802  which is coupled to a microprocessor  803  and a ROM  807 , a volatile RAM  805 , and a non-volatile memory  806 . The microprocessor  803 , which may be a Pentium processor from Intel Corporation, is coupled to cache memory  804  as shown in the example of  FIG. 22 . The bus  802  interconnects these various components together and also interconnects these components  803 ,  807 ,  805 , and  806  to a display controller and display device  808 , as well as to input/output (I/O) devices  810 , which may be mice, keyboards, modems, network interfaces, printers, and other devices which are well-known in the art. Typically, the input/output devices  810  are coupled to the system through input/output controllers  809 . The volatile RAM  805  is typically implemented as dynamic RAM (DRAM) which requires power continuously in order to refresh or maintain the data in the memory. The non-volatile memory  806  is typically a magnetic hard drive, a magnetic optical drive, an optical drive, or a DVD RAM or other type of memory system which maintains data even after power is removed from the system. Typically the non-volatile memory will also be a random access memory, although this is not required. While  FIG. 22  shows that the non-volatile memory is a local device coupled directly to the rest of the components in the data processing system, it will be appreciated that the embodiments of the present invention may utilize a non-volatile memory which is remote from the system, such as a network storage device which is coupled to the data processing system through a network interface such as a modem or Ethernet interface. The bus  802  may include one or more buses connected to each other through various bridges, controllers, and/or adapters, as is well-known in the art. In one embodiment, the I/O controller  809  includes a USB (Universal Serial Bus) adapter for controlling USB peripherals. 
         [0142]    In conclusion, the present invention provides for low cost and highly efficient security safeguards for standard TCP/IP Servers deployed on private and public IP networks. A method for creating secure subnetworks on a general purpose network disclosed in this invention is based on the SNT technology. SNT is a combination of traditional security methods and an innovative standards-based approach to authenticating and protecting network traffic. SNT provides a wide variety of security options for establishing a secure data pipeline between servers, with the capability of authenticating each connection tunneled within this pipeline. SNT provides an authentication capability to back-end systems, which are otherwise incapable of authenticating themselves, to enable them to communicate with servers and other peers in a secure fashion. 
         [0143]    SNT is a software solution and its deployment does not require installing any additional hardware. Since SNT is deployed in the IP stack, applications are unaware of its presence and keep running “as-is” without any changes. Due to SNT&#39;s point-to-point nature and its use of well-known technologies, there is no requirement for reconfiguring the network or for opening additional ports on interdepartmental firewalls. SNT may reduce the number of open firewall ports, because multiple application level protocols can be tunneled through a single secure pipe. With SNT, TCP/IP servers remain cloaked to all except authorized parties. Unauthorized parties cannot even identify open ports on the servers, and therefore cannot gain access. 
         [0144]    In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will be evident that various modifications may be made thereto without departing from the broader spirit and scope of the invention as set forth in the following claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense. 
         [0145]    It should also be noted that there are many alternative ways of implementing the methods and apparatuses of the present invention. It is therefore intended that the following appended claims be interpreted as including all such alterations, modifications, permutations, and substitute equivalents as fall within the true spirit and scope of the present invention.