Method and system for monitoring and controlling network access

A method and system for monitoring and controlling network access includes non-intrusively monitoring network traffic and assembling data packets that are specific to individual node-to-node transmissions in order to manage network access both inside and outside of a network. A rules base is generated to apply at either or both of the connection time and the time subsequent to connection. With regard to a particular node-to-node transmission, the data packets are assembled to identify the source and destination nodes, as well as contextual information (i.e., ISO Layer 7 information). The access rules are applied in a sequential order to determine whether the transmission is a restricted transmission. The rules are maintained in a single rules base for the entire network and are distributed to each monitoring node. Any of the protocols in the suite of TCP/IP protocols can be managed. The result of an analysis against the rules base causes a connection attempt to be completed or denied, a previously established connection to be broken, logging to occur, or a combination of these and other actions. Data collected during connection attempts or during a connection's lifetime may be passed to a third-party hardware or software component in order for independent validation to take place. Traffic monitoring and access management can be executed at a node other than a choke point of the network.

TECHNICAL FIELD
 The invention relates generally to a method and system for managing access
 control to resources of a distributed network, and relates more
 particularly to monitoring and controlling computer users' access to
 network resources from both inside and outside the network.
 BACKGROUND ART
 There are a number of available topologies for computer networks of nodes.
 A computer network may be highly centralized, having a mainframe computer
 that is accessed by a number of user computers, such as desktop computers.
 Currently, the trend is away from centralization and toward distributed
 processing and client-server relationships. In a distributed network,
 intelligence and processing power are distributed among a number of
 network nodes, typically with client workstations communicating with
 distributed servers. Other relationships among nodes of a network are
 known.
 A network of nodes may be associated with a single enterprise, such as a
 local area network (LAN) of a particular business. Such a network enables
 communications and data exchanges among the various nodes of the network.
 A single protocol may be used in the accessing of resources within the
 LAN. Thus, when a first node, such as a client workstation, accesses the
 computing resources of a second node, such as a server for storing various
 applications, data is exchanged without requiring a protocol conversion.
 However, the largest and most pervasive network is the nonproprietary
 global communications network referred to as the Internet. A number of
 different network protocols are used within the Internet. Protocols that
 fall within the Transmission Control Protocol/Internet Protocol (TCP/IP)
 suite include the HyperText Transfer Protocol (HTTP) that underlies
 communications via the World Wide Web, TELNET for allowing access to a
 remote computer, the File Transfer Protocol (FTP), and the Simple Mail
 Transfer Protocol (SMTP) to provide a uniform format for exchanging
 electronic mail, as well as a number of standardized or proprietary
 protocols for multimedia and broadcast services.
 An implementation of these and other Internet protocols solely within an
 organization is often referred to as an Intranet, while the use of such
 protocols across a restricted set of Internet sites that are relevant to a
 particular organization is referred to as the organization's Extranet.
 Much attention has been given to installing computer network gateways which
 focus on ensuring that potential intruders (sometimes referred to as
 "hackers") cannot gain illegal access via the Internet to an
 organization's computing resources on their Intranets. These gateways are
 "choke points," through which network traffic that is to be controlled
 must flow. Such "firewalls" are configured to allow any outbound
 connection or traffic to occur, but to restrict inbound traffic to
 specific services that are deemed to be non-threatening to the
 organization. Firewalls may also perform a limited amount of "packet
 filtering," which attempts to control traffic by reference to
 non-contextual, low-level network packets.
 An issue that receives less attention is ensuring that the employees of an
 organization are appropriately managed. This management extends to
 accessing external computer resources and accessing internal computer
 resources. The management may be set forth in an access control policy of
 the organization. With respect to many aspects, the management is the
 converse of the problem that firewalls are intended to solve. While
 firewalls are focused on keeping intruders from gaining unwanted accesses,
 access control systems are focused on ensuring that insiders are managed
 according to the access control policy of the organization.
 There are a number of motivations for implementing an access control policy
 within an organization. With regard to controlling external
 communications, two important reasons are maximizing employee productivity
 by ensuring that Internet access is used primarily for business purposes
 and maximizing the Internet-connection capability (i.e., bandwidth) of the
 organization, particularly during peak usage times. For example, using
 streaming audio and video services at peak times of the day in terms of
 the network traffic of an organization can seriously diminish productivity
 of other users within the organization who are attempting to perform tasks
 such as e-mail file transfers, terminal emulations, and network database
 inquiries.
 Using traditional approaches, organizations apply stringent rules and
 sometimes overbearing management dicta in order to prevent key business
 usage of the Internet from being adversely affected by casual or
 inappropriate usage. The traditional approaches are typically
 administratively difficult to set up and maintain, as well as being
 difficult to scale from small organizations to large enterprises. Thus,
 some of the productivity gains are negated by management overhead.
 One traditional approach to providing access control with regard to
 resource requests generated within a network is to leverage firewall
 technology and focus on the well-known packet filtering techniques. This
 typically requires a computer system to be installed as a router with at
 least two network interface cards and with no data packets being allowed
 to be forwarded from one interface card to the other without prior
 filtering. That is, firewall technology has been "turned around" to form
 some degree of protection. Rather than controlling outsiders attempting to
 access resources of the network, the techniques are used to control
 insiders attempting to access external resources. This approach may work
 well in some applications, but in others the approach is too simplistic
 and inflexible.
 U.S. Pat. No. 5,727,146 to Savoldi et al. describes a method for securing
 network access to a network. All data packets that are transmitted via the
 network are monitored for authorized source addresses, rather than
 examining only the initial network connection packets. Thus, network
 access to a port is secured by monitoring the source address of each
 packet that is sent as a device tries to train to the port of the network.
 If the source address matches an authorized source address assigned to the
 port to which the device is attached, the device is allowed access to the
 system. However, if the device attempts to train with a source address
 different from the authorized source address, all packets sent by the
 device are denoted as errored packets to prevent them from being accepted
 by any other device in the network. By monitoring all packets, the system
 detects occurrences in which a device attempts to "disguise" itself by
 first training with an authorized source address and then sending a packet
 with an unauthorized source address.
 Another approach to implementing network access control is to add
 third-party software modules into commercially available proxy server
 products. For example, software modules that are dedicated to attempting
 to control access may be added to a web proxy server. The disadvantages of
 this approach include the fact that only a small subset of Internet
 protocols is actually routed through a web proxy server. These protocols
 are typically restricted to browser-based FTP, Gopher and WWW protocols.
 This subset of protocols does not include the protocols used in the
 transfer of packets for e-mail, telnet, other file transfers, and
 streaming audio and video. Therefore, using web proxy servers as choke
 points allows only an incomplete level of control.
 Another approach to attempting control access is to establish "blacklists"
 or "control lists" into proxy servers or into individual client
 workstations. This is a somewhat simplistic approach to meeting the needs
 of organizations and is often administratively burdensome to corporations,
 since the lists must be updated on a regular basis.
 What is needed is a method and system for providing access control to
 resources of a network in a manner that is flexible, scalable and
 relatively easy to administer.
 SUMMARY OF THE INVENTION
 A method and system in accordance with the invention are configured to
 provide access control to resources of a network by collecting and
 assembling data packets of a specific transmission, so as to enable
 identification of information from raw data packets at the lowest level to
 application-level data at the top-most level. In terms of the standardized
 model referred to as the International Standards Organization (ISO) model,
 the data packets are assembled to determine not only the lower-layer
 information from the headers of the packets, but also the uppermost
 Application Layer (i.e., Layer 7) contextual information. Access rules are
 then applied to determine whether the specific transmission is a
 restricted transmission.
 In the preferred embodiment, the steps of receiving and assembling the data
 packets occur non-intrusively with respect to impact on traffic flow
 through the network. That is, the data packets are intercepted without
 impact on network performance, unless a restricted transmission is
 detected. Receiving and assembling the data packets may occur at a
 workstation or server that is dedicated to providing access control. For
 example, a free-standing workstation may be connected as a node to the
 network and may be switched to a promiscuous mode in order to receive all
 data packets transmitted to or from other nodes of the network. This
 allows the workstation to receive the fragments (i.e., data packets) of
 each access attempt from elsewhere on the network to either external
 destinations or other internal destinations. The fragments are pieced
 together to identify ISO Layer 7 information, as well as lower layer
 information. In an e-mail context, the Application Layer information of
 interest may include the information contained within the "to," "from" and
 "subject" lines of e-mail messages. In a web context, the Application
 Layer information of interest may include the text of the HTML pages.
 By placing the dedicated workstation or server outside of the direct paths
 from source nodes to destination nodes, the impact on network traffic is
 minimal. However, the method and system may also be implemented by
 examination and management at a choke point, such as a proprietary proxy
 server, a firewall or other network node that is acting as a gateway
 between the network and an external network (e.g., the Internet). The
 examination and management at a choke point may take the form of a plug-in
 module for receiving, assembling and examining data packets in the manner
 described above. However, the examination of access attempts at the choke
 point will not provide the level of access control available by monitoring
 all traffic within the network, and may well impact network performance.
 Therefore, the system may include both access monitoring at the choke
 point and non-intrusive monitoring elsewhere on the network.
 In the approach in which access is examined non-intrusively, the dedicated
 workstation or server may be configured as a "bare-bones" TCP/IP virtual
 machine to establish a capability of providing information extending from
 the lower layers of the ISO model to the Application Layer. There may be
 more than one dedicated workstation or server, particularly if the network
 is divided into segments. The access rules are preferably stored as a
 rules base, which may be centralized if there is more than one node that
 provides access management. Alternatively, the rules base is configured at
 a single site, but then automatically distributed to each access control
 point on the network.
 The access control rules may apply at the time that a connection is
 established or may depend upon application protocol data following a
 successful connection. In the preferred embodiment, the rules are applied
 both at the time of connection and subsequent to the connection, as data
 packets are assembled. If a node-to-node transmission is determined to be
 a transmission that is restricted by the rules base, a connection attempt
 may be denied, a previously established connection may be broken, a simple
 logging may occur, or a combination of these actions may be implemented.
 Data collected during the connection attempts or during a connection's
 lifetime may be passed to third-party software in order for independent
 validation to occur. However, this is not critical.
 The rules base is preferably divided into two sets of rules. The first set
 relates to access management requirements with regard to outgoing
 connection attempts, while the second set relates to internal connection
 attempts. The rules within each set may be layered in order to allow
 seemingly inconsistent rules to be included in a single rules base. For
 example, rules within a particular set may be applied sequentially, so
 that a specific rule application is accessed prior to a general rule
 application that contradicts the specific rule. The rules base is
 preferably configured in terms that are familiar to users, such as
 usernames, group names, workstation identifiers, destination addresses and
 URLs, services required, time-of-day, day-of-week, and data size.
 An advantage of the invention within a business environment is that the
 method and system protect employee productivity by ensuring that Internet
 access is used primarily for business purposes. Another advantage is that
 the bandwidth availability is used more efficiently. Access may be
 dynamically controlled based upon factors such as the time of day and the
 day of the week. Another advantage is that internal security is enhanced
 by ensuring that access to internal computer resources is managed.

DETAILED DESCRIPTION
 With reference to FIG. 1, an exemplary network is shown as including a
 router 10 that provides access to the global communication network
 referred to as the Internet 14 for an organization that is protected from
 unwanted intruders by a firewall 16. A number of conventional user
 workstations 18, 20 and 22 are included as nodes of the network. A fourth
 workstation 24 may be identical to the other workstations, but is
 dedicated to providing access control management. Thus, the workstation 24
 is an access control management console (ACMC). However, one of the other
 workstations may be used to implement the access rules in a manner that is
 consistent with the non-intrusive management system to be described below.
 The workstation 24 may be a conventional desktop computer having a plug-in
 access management module 26 to monitor traffic within the network.
 Another node within the network is a proprietary proxy server 28 that is
 used in a conventional manner to enable selected services, such as web
 services. A web proxy server is designed to enable performance
 improvements by caching frequently accessed web pages. While such servers
 tend to add some access control potential by taking advantage of the fact
 that all HTTP conversions are being channeled through the service, the
 access control functionality is not a primary focus and only a subset of
 the protocols that are likely to be encountered via the Internet will be
 recognized by conventional web proxy servers. For example, the proxy
 server 28 may provide proxying capability for the HTTP protocol and
 perhaps browser-based FTP and Gopher, but the proxying capability is not
 likely to extend to other TCP/IP application protocols, such as telnet,
 news, e-mail and many proprietary multimedia protocols.
 The network topology of FIG. 1 is shown as an exemplary configuration and
 is not meant to limit or constrain the description of the invention. The
 method and system to be described below can operate on a wide variety of
 network configurations. Moreover, while all workstations 18-24 can be
 presumed to be running the Microsoft Windows operating system and all
 servers 28 can be assumed to be running the Microsoft Windows NT Server
 operating system, the invention is not specific to any one operating
 system. Although the prime use of the method is anticipated as being
 applied to networks using the TCP/IP protocols, it can be readily adapted
 to function with any other set of networking protocols, such as Novell
 IPX/SPX or IBM NetBEUI.
 It is also assumed that the network for which access management is to be
 provided includes a number of users, groups of users and workstation
 addresses. All of these items are assumed to have been pre-configured
 using known configuration methods provided by the supplier of the network
 operating system. Although implementation of the invention may be based on
 data such as usernames and group names from a network operating system or
 similar repository, there is no dependency on a specific network operating
 system or a specific mechanism to access such data. Employing usernames
 and group names that are consistent with other system operations takes
 advantage of any familiarity that may already exist with this information.
 Furthermore, in the absence of any such information, the invention may
 utilize other naming nomenclature, such as IP or Ethernet addresses.
 Referring now to FIG. 2, a first access control module 30 has been
 installed on the workstation 18 to enable the workstation to function as a
 passive access control station (S). A second instance of an access
 control module 32 is installed on the proxy server 28, so that this node
 functions as a proxy access control station (PRACS). Moreover, a third
 instance of an access control module 34 is installed on the firewall 16 in
 order to form a gateway access control station (GACS). A key point in the
 system and method is that the individual workstations 20 and 22 that are
 accessed by users can be managed without installing any software
 components specifically on those workstations. Network traffic is
 monitored and access to internal and external resources is controlled and
 managed either at choke points (represented by the proxy server 28 and the
 firewall 16) and/or non-intrusively at nodes which are not choke points
 (represented by the workstation 18). The access control modules 30, 32 and
 34 can be installed, de-installed, and reinstalled on any of the nodes of
 the network at any time to suit potentially changing network topologies or
 changing access management policies.
 The location and configuration of each of the access control modules 30, 32
 and 34 are selected by an installer based upon pragmatic factors in order
 to achieve a level of access control that is consistent with the access
 management policy. As previously noted, the first access control module 30
 is not required, since the workstation 24 may serve the dual purpose of
 allowing a system operator to configure the rules base of access rules and
 non-intrusively monitoring traffic along the network. The second access
 control module 32 is optionally used in order to ensure that access is
 managed for all users who are accessing the WWW by configuring web
 browsers to operate via the proxy server 28. The third access control
 module 34 is optionally installed at the firewall 16 in order to validate
 that both the firewall and the other access control modules have indeed
 been configured correctly and are performing their desired duties.
 Firewalls are sometimes difficult to configure, so organizations are
 increasingly adding second-line checks to their networks to ensure that
 absolute integrity is being maintained. However, the non-intrusive
 monitoring at the dedicated workstation 18 is capable of monitoring and
 controlling all access from all nodes on the network, regardless of TCP/IP
 protocol. This mechanism can be used to manage all network access that is
 not routed via the proxy server 28 with a high degree of probability that
 undesired access can indeed be blocked. Network traffic is non-intrusively
 monitored, but the system and method may be used to proactively block any
 requests for resources.
 The non-intrusive monitoring of network traffic at the workstation 18
 occurs by receiving and assembling data packets of node-to-node
 transmissions. Modern networks, including the Internet, are packet
 switching networks in which a transmission is separated into data packets
 which are separately transmitted to a destination node. At the destination
 node, the packets are assembled to form the original composite signal.
 FIG. 3 depicts an Ethernet data packet according to RFC base 894. Traffic
 along the network of FIGS. 1 and 2 may be in the form of transmissions of
 Ethernet packets. Each Ethernet packet 36 includes five segments. A first
 6-byte segment 38 identifies the destination node address, while a second
 6-byte segment 40 identifies the address of the source node. The third
 segment 42 is a 2-byte segment that identifies the protocol type. A data
 field 44 has a variable length, with a maximum of 1500 bytes. The data
 field 44 contains the user information. Finally, the fifth segment 46 is a
 checksum field that is used for error detection and correction purposes.
 As is well known in the art, other standards for packetization are
 utilized. For example, each header that is used in a TCP transmission or a
 UDP (User Datagram Protocol) transmission includes a 16-bit destination
 port number. An Ethernet packet having a TCP/IP packet or UDP/IP packet
 embedded in its data field will include three designations: (1) the
 Ethernet addresses of the source and destination nodes; (2) the IP
 addresses of the source and destination nodes; and (3) the IP port number
 of the destination node. Other protocols are present and operational in
 TCP/IP networks and control operations such as routing and the translation
 of IP addresses to and from hostnames. A protocol referred to as ARP
 (Address Resolution Protocol) also maps IP addresses to Ethernet
 addresses.
 By intercepting the Ethernet packet 36 of FIG. 3, the destination address,
 the source address and the user data are available to the monitoring node.
 For the non-intrusive monitoring that occurs at the workstation 18 of FIG.
 2, the workstation may be placed in the promiscuous mode and there will be
 no impact on performance of the network. However, the packets that are
 specific to a particular node-to-node transmission can be collected and
 assembled merely by configuring the access control module 30 such that the
 workstation functions as a bare-bones TCP/IP protocol virtual machine. The
 workstation then has the capability of piecing together the fragments of a
 multi-packet signal. This enables access management control to base
 decisions upon information from various levels of the ISO model--from the
 lower layers to the uppermost Application Layer.
 Communications protocols are a layered set, often referred to as a "stack."
 The International Standards Organization (ISO) has developed a model
 referred to as the ISO 7-layer model, which serves as a basic reference.
 Each layer represents a particular function. The function of a particular
 layer may be executed in hardware or software or a combination of hardware
 and software. At times, a single program performs the functions of more
 than one layer. FIG. 4 illustrates the seven layers of the ISO model. The
 lowermost layer, referred to as the Physical Layer 50, is the hardware
 network connection, such as a physical wire. ISO Layer 2, the Data Link
 Layer 52, is responsible for providing reliable transmissions of data.
 Layer 2 may be a network interface card that links a computer to the
 network.
 ISO Layer 3, the Network Layer 54, is the network software for routing
 packets throughout the network. ISO Layer 4, the Transport Layer 56,
 transports data from the network to the upper levels of the ISO model.
 ISO Layer 5, the Session Layer 58, deals with establishing network
 sessions. Logical connections are established based upon a request of a
 user. ISO Layer 6, the Presentation Layer 60, deals with the presentation
 of data to an application which resides at ISO Layer 7, the Application
 Layer 62. Examples of the Application Layer include FTP, HTTP and SMTP.
 Layer 7 provides access to the Internet for a user.
 FIG. 4 illustrates three inputs to a step 64 of storing data packets. The
 first input 66 represents the actual input of data packets, while the
 second and third inputs 68 and 70 are operational representations.
 Referring to FIGS. 2 and 4, the workstation 18 that non-intrusively
 monitors network traffic receives inbound and outbound data packets
 through Layers 1 and 2. As previously noted, the network interface card of
 Layer 2 is set to the promiscuous mode, so that the data packets of the
 network are received over the Physical Layer 50. Optionally, the rules
 base of the access management module 26 may be utilized more than one
 time. In a first application of the rules base, the first packet of a
 resource request may be used to detect the source and destination nodes,
 allowing access determinations to be based on this low-level information.
 However, higher level decisions can be formed only after a connection has
 been established and the actual content has begun to flow over that
 connection. This is in contrast to conventional operations of firewalls,
 which typically only act as low-level packet filters (i.e., at ISO Layer
 2).
 As indicated by the input 68, the invention includes assembling the data
 packets to detect information at the Transport Layer 56 and the Network
 Layer 54 of the ISO model. Moreover, Layer 7 information is acquired by
 assembling the data packets, as represented by the input 70. For example,
 in an e-mail environment, the Application Layer information that may be
 relevant to application of the rules base may include information within
 the "subject" line of an e-mail message. This information is acquired only
 upon accessing the data fields of the data packets of the e-mail message.
 At step 66, the necessary information has been acquired for applying the
 rules base. As previously noted, the application may occur more than once
 for a single multi-packet transmission. The desirability of providing
 single or multiple rules applications may depend upon a number of factors.
 Referring now to FIG. 5, an embodiment of a graphical user interface (GUI)
 68 is shown for use by a system operator to configure the rules base that
 determines the action of the access control modules 30, 32 and 34 of FIG.
 2. The action of each access control module is determined by rules
 configured at the ACMC 24, which includes the access management module 26.
 The management module presents the GUI 68, although this is not critical
 to the invention.
 In the preferred embodiment, the rules base is comprised of a twin set of
 ordered rules. One of the sets of rules relates to access management
 requirements for outgoing access, while the second set relates to inbound
 connection attempts. Within each set, the rules are in a sequence that
 dictates the sequence in which the rules are considered. This sequencing
 ensures that rules are applied in a specific deterministic order, allowing
 the system operator to layer more specific rules ahead of more general
 rules. Thus, seemingly inconsistent rules can be established. For example,
 a rule may be configured to give User A access to a certain resource ahead
 of a rule banning everyone in the organization from accessing that
 resource. This has the effect of allowing access by User A and blocking
 access to that resource by all other users.
 After a rules base has been configured by a system operator, the rules base
 is downloaded to the access control modules 30, 32 and 34. Thus, any
 subsequent changes in the rules base may be implemented at the various
 nodes in an efficient dynamic manner.
 Regarding the configuration of the rules, various objects may be utilized
 to provide a more granular or less granular rule. Affected parties may be
 designated by usernames and group names (both typically from the network
 operating system), ad hoc groupings of users, and workstation addresses.
 Other objects include network services, source addresses (IP address,
 hostname or URL), destination addresses (IP address, hostname or URL) and
 time-slot specifiers (time of day, day of week, etc.). These objects are
 graphically dragged and dropped onto each rule, as required in order to
 dynamically and graphically build up the rule within the overall rules
 base. Against each rule, an action is configured to specify the resulting
 action that should be performed if a rule is matched at runtime. Potential
 actions include (1) disallowing the connection attempt, (2) allowing the
 connection attempt to be completed, (3) passing off the decision-making on
 whether the connection should be allowed or disallowed to a third-party
 component (which may, for example, consult a control list or perform other
 checks), (4) allowing the connection, but performing further analysis on
 the data stream in order to determine whether a connection should be
 broken at some future point (e.g., based upon the number of bytes that are
 transferred), and (5) performing further collection of the data stream and
 passing off the collection to a third-party component for further analysis
 (e.g., an anti-virus product).
 Rules can be amended, deleted or reordered using the graphical user
 interface 68 of FIG. 5. The rules base is stored in an internal format
 that is then made available to the various access control modules 30, 32
 and 34, as described above.
 The graphical user interface 68 is divided into two portions. The lower
 portion 70 is used to define network objects, such as usernames, groups,
 workstations and other such entities mentioned above. This information is
 built up by the system operator, but as much information as possible is
 gleaned from the network operating system. Typically, all usernames, group
 names and workstation addresses are established via reference to the
 network operating system. It is also possible to form ad hoc groupings for
 ease of use, such as groupings of users that are not configured or that
 are configured differently in the network operating system.
 Object-oriented technology simplifies the definition process by allowing
 operational parameters to be defined for object classes, rather than each
 individual network element. It is thus possible to perform access control
 at a detailed level of controlling individual user access and at a more
 general level of network groups of users or ad hoc groupings of users.
 This allows the operator to have flexibility in the access management
 task. It is thus possible to allow different access control criteria to
 different levels of employees and managers.
 Other objects that are defined in the lower portion 70 of the GUI 68 are
 services, such as e-mail, file transfer, WWW and any of the other possible
 sets of services allowed in a TCP/IP network. Specific properties of a
 service include its name and its TCP/IP port number. Certain well-known
 services are pre-configured for the operator. For example, it is known
 that the telnet service should be pre-configured on port 23. Any services
 may, however, be added or modified by the operator.
 The upper portion 72 of the GUI 68 contains the rules. The total set of
 rules is referred to as the rules base. Rules are constructed graphically
 by the operator by dragging objects from the lower portion 70 and dropping
 them into specific rules of the upper portion 70. Rule ordering is
 important and can be changed graphically by dragging a rule to a new
 position in the sequence. When rules are consulted at runtime, a top-down
 ordering is implemented. As previously noted, two sets of rules are
 maintained, one relating to outbound communications and the other relating
 to inbound communications.
 In the preferred embodiment, storage logs are maintained for transaction
 data. The storage logs may be maintained for all of the transaction data
 or subsets of the data. The storage logs may then be used for further
 analysis by built-in or third-party components. However, this is not
 critical to the invention.
 FIG. 6 is an exemplary arrangement of hardware and software for
 implementing the network access control system and method. A Passive
 Access Control Station, such as the workstation 18 of FIG. 2, includes an
 input port 74 that is placed in a mode to receive all data packets
 destined for any node on the network. The data packets that are specific
 to a particular node-to-node transmission are combined at a packet
 assembler 76. Detailed information from the assembled data packets is
 stored until sufficient information is acquired regarding the node-to-node
 transmission to apply the previously configured rules base 70. The process
 of applying the rules base to the acquired information may occur in a
 single step or may be a multi-step process. For example, in FIG. 6 there
 is a state identifier 80 and a context identifier 82. The state identifier
 is used to determine information regarding the lower layers of the ISO
 model, while the context identifier 82 acquires higher layer information,
 including Application Layer information. The rules base 78 may be
 consulted a first time when the state identifier 80 has acquired
 sufficient information, and then applied a second time when the context
 identifier 82 has acquired sufficient higher level information.
 It is important to note that information which is stored includes both low
 level state information and contextual information that is discovered at
 points in the network stack other than Layers 1 and 2. Full Application
 Layer awareness is achieved without the need to implement specific
 application proxies for each service. The two parts of the proxy process
 are linked in order to accommodate the possibility that proxy connections
 are being made, since the real source node and the final destination node
 must be identified to ensure that the correct rule is applied in managing
 network access.
 If it is determined that a particular node-to-node transmission is
 unrestricted, the transmission is unaffected by the process. Optionally,
 data regarding the transmission may be stored within a log 84. However, if
 the transmission is a restricted transmission, any one of a number of
 actions may be initiated by a connection controller 86. When the
 connection from a source node to a destination node has not been
 completed, the connection controller may generate a signal that is output
 via the output port 88 to an appropriate node (e.g., a router) for
 preventing the connection. For situations in which the connection is
 established, the controller 86 may generate a signal that disables the
 connection. As a third alternative, the connection may be allowed, but
 further analysis of the data stream may be performed in order to ascertain
 whether the connection should be disabled at some future time (e.g., based
 upon the number of bytes that are transferred during the connection). The
 decision of whether to allow or disallow the connection may be passed to
 another node, such as a third-party component which consults a control
 list or performs other checks.
 FIG. 7 details the steps of providing access control in accordance with the
 invention. In step 90, network traffic is monitored non-intrusively, such
 as by the workstation 18 of FIG. 2. Packets that are specific to a
 particular communication (i.e., node-to-node transmission) are identified
 in step 92 and assembled in step 94. Decision step 96 determines whether
 sufficient information has been acquired to apply the rules of the rules
 base.
 When sufficient information has been acquired to apply the rules base, the
 first rule is consulted to determine if the packet information set matches
 the rule. As previously noted, the rules base is organized into a first
 set of outbound-related rules and a second set of inbound-related rules.
 Moreover, the rules in a particular set are consulted in a top-down order.
 Thus, the rule that is applied in step 98 is the first rule in the
 appropriate set of rules. At step 100, a decision is made as to whether
 the information set fits the rule applied in step 98. If a rule fit is
 recognized, the appropriate rule action is applied at step 102. The
 appropriate rule action may be designated within the rules base. If the
 rule is affirmatively stated (e.g., "allow all HTTP connections"), the
 action will allow the connection to remain unhindered. Other prescribed
 actions may include logging information to a database, sending an e-mail
 message, raising an alert in a pre-established manner, or diverting the
 data content of the connection to a third-party process which can
 determine whether the connection should be maintained by referencing other
 data, such as anti-virus rules or one or more control lists.
 If in the decision step 100 it is determined that the first rule is not
 applicable, decision step 104 determines whether there is another
 applicable rule. If there are fifteen rules within the set of rules that
 are applicable to the communication under consideration, steps 98, 100 and
 104 will be repeated fifteen times or until the information set matches
 one of the rules.
 Preferably, there is a default rule at the end of each set of rules in the
 rules base. Referring briefly to FIG. 5, the GUI 68 shows six rules in its
 set of outgoing rules in the upper portion 72 of the GUI. The sixth and
 final rule to be applied is the default rule that disallows outgoing
 communications that are not specifically allowed within the set.
 Alternatively, the default rule may be to allow the communication.
 After all of the appropriate rules have been applied, the optional decision
 step 106 is executed. The access rules of the rules base are pre-parsed to
 identify which rules can be applied at the basic connection time and which
 rules need to be held-over for application once the connection is
 completed and data is flowing. If, for a particular node-to-node
 transmission, it is determined that no rules need to be held-over, the
 default rule can be applied at connection time, assuming that there is no
 prior rule that provides an affirmative response at step 100. However, if
 access rules need to be applied once data is flowing, the default rule is
 applied with the held-over rules. Thus, when there are access rules that
 relate to data flow, the connection is allowed to be completed, unless it
 is determined at step 100 that the connection is a restricted one. If it
 is determined at step 106 that rules have been held-over, the packets
 continue to be assembled at step 94 and the process repeats itself in
 order to apply the held-over rules. On the other hand, if there are no
 held-over rules, the process returns to the step 92 of identifying packets
 of a specific communication. However, the implementation, and even
 existence, of step 106 is not critical to the invention.
 It is worth noting that various changes and modifications can be made to
 the above examples to achieve the same results, while remaining within the
 scope of the method and system. For example, access management control can
 be performed on a generic gateway machine, as opposed to a firewall, a
 proxy server or a passive workstation.