Abstract:
A method and system is disclosed for cross-correlating information between the domains of network management and network security. The present invention discloses a model representing the security domain that can be used to define relationship between devices and events in the security domain in the context of a managed network. With this model, a security topology of the network security domain can be created based on the current implementation of the network. This model and topology allows the present invention to correlate relevant network security information to diagnose problems as they occur by using events detected within the network. Using the disclosed method and system for correlating information in the network security, the present invention provides further enhancements over conventional methods by cross-correlating information between the network security and network management domainsto aid in their detection and analysis of problems. Cross-correlating information across network security and network management domains enhances the ability of the present invention to diagnose problems that may arise in the network to allow an operator to get a more complete view of the system with minimal effort.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims priority from U.S. Provisional Patent Applications Serial No. 60/342,887, filed on Oct. 25, 2001; and No. 60/344,404, filed on Nov. 9, 2001. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to the field of network security, and, more particularly, a method and system for performing comprehensive network fault analysis by cross-correlating network security information and network management information.  
           [0004]    2. Description of the Related Art  
           [0005]    Computer networks and related systems produce a tremendous amount of information related to network security. Analysis of this security information as well as information related to network management is needed for network security purposes. Originally, networks had few automated functions. A human operator was generally responsible for providing network security. As networks became more complex, it became more difficult for an operator to effectively provide security. Therefore, it has long been desired to develop tools to aid operators and administrators in securing the network. Generally, tools of this nature only focused on a single domain, for example, either network management or network security. Because many tools only focus on information provided within the realm of one domain, they may supply information which inaccurately or incompletely describes the state of the network as a whole. Although generally related to relatively different domains, information from the network management domain may impact the analysis of information in the network security domain and vice versa. Thus, there is a need to cross-correlate information between tools monitoring the network security and network management domains for a more accurate and comprehensive understanding of overall network status. But because conventional methods, in their respective domains, are not necessarily compatible with each other, there is also a need to develop techniques for correlating information in the network security domain that are compatible with the conventional methods already developed for network management.  
           [0006]    In addition, network management tools have typically advanced at a more rapid pace than security tools. There is a wide variety of conventional software products available that aid an operator in managing a network. For example, a system might have network management software that would alert the operator when a component was malfunctioning. Some other conventional methods use more sophisticated fault analysis tools such as event correlation and root cause analysis tools (for example, rule-based reasoning, case-based reasoning, generic models, probability networks, model-based reasoning) to aid in automating management of a network. However, many existing methods have not proven to be an adequate solution for modern systems because they lack extensibility, have performance difficulties in some systems, may have large storage requirements, need to be constantly updated/configured, and are unable to compare information across domains.  
           [0007]    One fault analysis solution that has applied event correlation to the network management domain is described in U.S. Pat. No. 5,528,516, No. 5,661,668, and No. 6,249,755. These patents disclose a method and system for fault analysis using event correlation with a causality matrix to solve the problem of fault isolation. Those patents describe using an object-oriented model of a managed network domain to develop a separate network topology for the physical system that relates the managed network devices to each other. In the method described in those patents, symptoms, problems, and their propagation through the system can be described for individual device types, independent of their configuration in a particular environment. One object-oriented model that has been applied to network management is the Common Information Model (CIM) from the DMTF (Distributed Management Task Force) industry consortium, which describes the generic physical and logical devices and their components in an enterprise network, and their relationships to each other. However, CIM does not suggest using the model for network security events.  
           [0008]    While many conventional solutions have been developed in the domain of network management, comparable solutions have not been developed for the domain of network security. Network security tools, such as encryption, firewalls, and intrusion detection systems, usually address specific security issues. Few conventional methods exist for correlating information between these security tools, and those that currently exist are generally married to the proprietary solutions of a particular vendor. Typical correlation methods collect messages such as those generated using Simple Network Management Protocol (“SNMP”) from the various tools and display them on a common user interface. These conventional methods rely on the operator to correlate much of the information manually to determine its significance, and may not be sophisticated enough for the complexity and volume of information in some modern systems. One example of security information messages between network security tools is the Internet Engineering Task Force Intrusion Detection Message Exchange Format (“IDMEF”), which attempts to define a common format for intrusion messages among heterogeneous vendors. The IDMEF standard does not suggest, however, an object model for representing network security events that would allow correlation of network security events. Thus, there is a need for better and more automated correlation of information in the domain of network security.  
           [0009]    Because the domains of network management and network security may be closely related, information from the security domain may affect the network management analysis and vice versa. Because of the limited view provided by existing fault analysis tools, fault recovery in either domain may be based on incomplete or inaccurate information. The severity of a security event can only be evaluated in the context of the network in which it occurs. For example, something as trivial as a DNS zone transfer may be perceived as a threat in the security domain by a simple security tool. Such a transfer may be acceptable, expected behavior, if it takes place within the protected network, between primary and secondary DNS servers. Alternately, it may simply be a mis-configured DNS server, in which case this observed “security symptom” is of more use to the network managers who must reconfigure the server. Finally, it may indeed be a security threat, if the zone transfer information is leaving the protected network enclave, and being collected by a malicious agent on the Internet, for example. Thus, there is a need to develop a fault analysis tool to correlate information in the network security domain that is compatible with an advanced network management method to allow for cross-correlation of information between the network management domain and the network security domain to provide a more comprehensive analysis of a system.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention is a tool designed to work with existing devices and applications to provide a more complete and accurate view of an entire managed network by cross-correlating information between the network security and network management domains. To accomplish this, the present invention describes a technique for analyzing network security that is compatible with conventional network management techniques by creating an object-oriented model for representing network security events in the context of managed networks. The present invention discloses an object-oriented model of the network security domain which can illustrate the relationships between security events, security devices and other security domain components. The network security model of the present invention also can illustrate the relationship between the objects in the network security model and objects in a network management model representing network management domain components. The present invention can create a security topology by instantiating specific instances of the objects defined in the network security model. Using the security topology, the present invention describes a system and a method for cross-correlating information between the network management and network security domains, including relating the security topology to the network topology. By cross-correlating network management information with network security information, the present invention provides a common operational view of the network and security domains that allows for comprehensive awareness and control of the system. The present invention takes advantage of the commonality between the network management and security domains, which are usually viewed in isolation, to give a unified view to an operator or administrator, and to perform automated functions without sacrificing the capabilities of the underlying tools.  
           [0011]    Cross-correlation is a mechanism by which the fault analysis tools for different domains each independently diagnose their own areas of responsibility, but information from one domain is compared with information from the other domain to provide a higher level true root cause for the detected problem(s). Often times, an event in one domain may appear to be trivial or innocuous, but when combined with the knowledge of another domain, takes on a more significant or serious meaning. For example, a mail service failure is a trivial problem from a network management perspective, as an administrator would simply restart the service or the host platform on which the service runs to correct the failure. However, when considered along with knowledge of the security domain, information that indicates that a mail server disabled as the result of an attack gives the problem a whole new level of severity, and can grossly affect the course of action that may be taken to solve the problem. Under these circumstances, simply restarting a host platform, as in the example above, could be disastrous from a security perspective, as it could eliminate vital forensic information for attack analysis. Also, knowledge of the type of attack and the type of target, combined with knowledge of the network topology, can indicate which similar targets on the same or other networks may be vulnerable to the same attack. Based on this combined information, administrators can be warned of vulnerabilities so that pre-emptive measures can be taken.  
           [0012]    The present invention also can automate many of the functions previously performed manually by an operator. In addition, the present invention, with knowledge of the physical network topology and security topology, can utilize information relating to any device present in the system. Thus, the present invention provides an operator with comprehensive information in a manner of presentation that would aid them the most, such as the hierarchical relationship between different components. Generally, the present invention provides a more complete analysis of the system than conventional tools and methods. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a block diagram of the Common Information Model network management core object model;  
         [0014]    [0014]FIG. 2 is a block diagram of a high-level security model in an embodiment of the present invention;  
         [0015]    [0015]FIG. 3 is a block diagram of a high-level security model in another embodiment of the present invention;  
         [0016]    [0016]FIG. 4 is a block diagram of a sample Security Information Model network security object model according to the present invention;  
         [0017]    [0017]FIG. 5 is a block diagram illustrating the relationship between the network security fault analysis tool and network management and network security correlation engines in an embodiment of the present invention;  
         [0018]    [0018]FIG. 6 is a block diagram of an example of an implementation of the present invention; and  
         [0019]    [0019]FIG. 7 illustrates an embodiment of the present invention in operation. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0020]    The disclosures of U.S. Provisional Patent Applications Serial No. 60/342,887, entitled System and Method for Correlation, Analysis and Display of Network Status and Security Events, filed Oct. 25, 2001, and No. 60/344,404, entitled System and Method for Correlation, Analysis and Display of Network Status and Security Events, filed Nov. 9, 2001, both naming Reuben S. Fischman and Adam Payne as inventors, are hereby incorporated herein by reference.  
         [0021]    The purpose of the present invention is to enhance the operation of a network by providing a more complete view of the network than provided by conventional methods. The present invention accomplishes this by cross-correlating information between the network security and network management domains. To efficiently cross-correlate between these domains, these domains preferably should have efficient and compatible methods for correlating information within their respective domains. An efficient method for correlating information has been previously developed for the network management domain. The preferred embodiment correlates information in the network management domain by leveraging the open-standard Common Information Model, shown in FIG. 1, to create a network management domain topology. One commercial application that implements this DMTF CIM is SMARTS InCharge by System Management Arts Inc., of White Plains, N.Y., which defines appropriate models for network devices corresponding to CIM. The SMARTS InCharge application uses codebook/causality matrix technology and can build a network topology. A detailed description of the InCharge application, the codebook/causality matrix and its application to the network management domain can be found in U.S. Pat. No. 5,528,516, No. 5,661,668, and No. 6,249,755, the disclosures of which are herein incorporated by reference.  
         [0022]    Because a comparable method is not available for network security, the present invention creates a network security model based on the CIM approach to object-oriented representations and relationships. The preferred embodiment accomplishes this by defining an object-oriented model of the security domain that maps out the relationship between security events, devices and other network security domain components in the context of a managed network. Although the preferred embodiment currently defines the network security model in the SMARTS InCharge event correlation tool, the present invention will work with any fault analysis tool that models network components based on the CIM, or any other object-oriented network management model that is capable of being extend to domains outside of network management.  
         [0023]    Once a security model has been created, the preferred embodiment creates a security topology of the network by instantiating specific instances of the objects in the security model to represent the security architecture, and additional objects as security events occur. In a similar fashion to the SMARTS InCharge technology, this security topology can be used to correlate information in the network security domain. Because the preferred embodiment is using compatible approaches for network security and network management correlation, the present invention can provide an even more comprehensive view of the entire managed network. Security managers using the present invention can have visibility into the status of the network, and network managers using the present invention can have visibility into the security posture of the network. In addition to visibility, information between these domains can be cross-correlated to automatically provide a more complete analysis into the status of the network for various viewpoints.  
         [0024]    The present invention is not just another specific tool to detect events, but rather a modular method for correlating and analyzing all of the available information and events in the network, and providing a combined network and security status picture. This is accomplished by developing a novel method for correlating network security information and utilizing existing network management correlation capabilities to cross-correlate information in a security topology with physical devices in a conventional network topology. In the preferred embodiment, a network security fault analysis tool is used to implement the present invention. The network security fault analysis tool of the preferred embodiment would typically reside within a system similar to a network management tool and would perform the network security correlation functions and the cross-correlation of information between the network management and network security domains. Of course, the software applications that comprise the network security fault analysis tool, network management tool and cross-correlation tools could reside on different physical computers and communicate information electronically.  
         [0025]    1. The Security Model  
         [0026]    In the present invention, a network security model is defined to relate security information (security events, devices, policies, and other network security domain components) to one another and to relate them to a managed network. A high-level security model  200  representing the generic relationships between elements in a network security event in the preferred embodiment is shown in FIG. 2. Model  200  is similar to the CIM and describes the generic elements and interactions of a security domain. Model  200  is an object-oriented model for describing and sharing the management information in a network system. Model  200  illustrates several security objects and their relationships to one another, as described below. From this model, the present invention can build a security topology for the domain of network security. Preferably, this model is an object-oriented model defining the relationship between security events, security devices, policies, and other security domain components in the context of a managed network.  
         [0027]    The focus of the network security model of the present invention is an attack  230 . FIG. 2 shows the relationship of the attack  230  to the analyzer  210  which detected the attack  230 , the malicious source (internal or external)  220  which launched the attack  230 , and the specific host(s)  240  and/or service(s)  250  that the attack  230  targets and affects. Analyzers  210  (also known as sensors) are the elements that represent the tools used to gather information, for example, intrusion detection systems that can detect attacks. Elements that can comprise this group include traffic analyzers, firewalls, and intrusion detection sensors. Sources  220  represent the attacker(s), which may be any source that would launch an attack, such as an outside individual, a foreign computer, or a misused or compromise internal asset. Typical examples of an attack  230  could be a virus, denial of service, unauthorized access, etc. Attacks  230  can include different types of attacks which have different relationships with different parts of the system. Hosts  240  represent the components of the system which host services  250  while services  250  represent particular services that may be targeted by an attack  230 . Servers, end-user computers, and network printers are all examples of possible hosts  240 . A particular service  250  may be located on several different hosts. Examples of services  250  may include e-mail, printing, or file transfers. Vulnerabilities  260  represent the weaknesses that a host  240  or service  250  may have, such as physical limitations (e.g. denial of service), bug(s) in the programming, or inadequate security.  
         [0028]    [0028]FIG. 3 shows another embodiment of a high-level generic network security model of the present invention. Similarly to FIG. 2, attacks  330  launched by sources  320  attack hosts  340  and target services  350  and are detected by sensors  310  (also known as analyzers). Vulnerabilities  360  represent the weaknesses that a host  340  or service  350  may have. Subscribers  370  represent the end users of the attacked service  350 .  
         [0029]    In order to create a specific network security object model, the preferred embodiment extends the CIM model to the network security domain, although the present invention will work with any object-oriented network management model that is capable of being extended. The CIM model represents an industry standard modeling structure that provides a means to model objects in a network and to build relationships between entities. The preferred embodiment extends the CIM Specification Version 2.2, including its Core model and relevant schemas such as Network, Policy and System, as would be known to one skilled in the art. FIG. 1 represents a class diagram of the standard CIM Core model. Computer systems  110  and services  120  are represented as sub-classes of logical elements  130  in a network.  
         [0030]    [0030]FIG. 4 shows one embodiment of a detailed network security object model in accordance with the present invention. Those skilled in the art would be able to construct different detailed object models based on the generic components and relationships identified in FIG. 2. The generic components and relationships of the network security model identified in FIG. 2 are specifically implemented by creating new sub-classes from the CIM Core model of FIG. 1. For example, malicious services  430  corresponding to attacks  230  of FIG. 2 are defined as a sub-class of the CIM_Service class  400 . Defining an attack  230  as a service  400  in the CIM model allows the present invention to take advantage of the underlying relationships in the CIM model. Specific types of attacks  431  are defined as sub-classes of the malicious service  430  and are hosted on the computer systems  440 , corresponding to the hosts  240  of FIG. 2, or services  400 , corresponding to services  250  of FIG. 2, which the attack  431  attacks or targets, respectively. Network security-specific devices such as firewalls  411  and intrusion detection systems  421 ,  422  may be sub-classed to represent the protection service  410  and detection service  420  that the devices provide, corresponding to the generic analyzers  210  of FIG. 2. The Network IDS (“NIDS”)  421  and Host IDS (“HIDS”)  422  intrusion detection systems represent sub-classes of detection services  420 . Specific detection services  420  that detect specific attacks  431  are a Distributed Denial of Service (“DDOS”) network sensor  423 , representing a specific NIDS  421 , and a host-based Change Detection Sensor (“CDS”)  424 , representing a specific HIDS  422 .  
         [0031]    Because the preferred embodiment creates its network security elements as extensions of the CIM model, the preferred embodiment can use the underlying CIM relationships to ascertain the interdependencies and impacts of successful and in-progress attacks  431 . For example, an attack  431  can be associated with all of the related alerts from the various detection devices represented as detection services  420  throughout the network. Because the security model is an extension of the CIM model used for network management, the security model also allows security events to be related to devices in the network model to allow correlation between the network security domain and the network management domain.  
         [0032]    Additionally, FIG. 4 defines the concept of a security zone  450 . A security zone  450  allows for a collection of nodes to be containerized into a security enclave. For example, a network monitored by an embodiment of this invention may have an internal security zone consisting of computer systems  440  inside a firewall  411 , computer systems  440  in a demilitarized zone (DMZ) (not shown), and computer systems  440  external to the firewall  411 . A detection service  420  such as a NIDS  421  can be associated with a security zone  450 . A firewall  411  can connect and therefore be associated with multiple security zones  440 . Policies  460  can be defined for specific security zones  450 .  
         [0033]    [0033]FIG. 5 shows a simplified class hierarchy and attribute level detail for the DDOS  530  and CDS  540  sensors corresponding to DDOS  423  and CDS  424  classes of FIG. 4. Because of the object oriented nature of the CIM model, many of the attributes can be inherited from classes higher in the hierarchy. For example, the name attribute  531 ,  541  should be an attribute of the root managed element  500  level. Other attributes are actually relationships. The HostPlatform attribute  542  of the CDS class  540  represents a relationship to the object representing the host platform running the CDS.  
         [0034]    2. Security Topology for the Network Security Domain  
         [0035]    Once a model has been developed, the present invention can create a security topology based on instantiating specific instances of objects defined by the security model in order to apply the fault analysis tool of the present invention to the security topology. In the preferred embodiment, the security topology based on the security model is usually created by processing events from various sources which may include, but are not limited to, syslog events, text logfiles, and Simple Network Protocol (SNMP) traps. Additionally, the system may interface in a modular fashion with existing tools that process events (e.g. vendor-specific managers or collectors), rather than processing events directly from the sensors themselves. As the network is discovered, security events, devices, and other network security domain components are mapped into their generic model definitions, creating specific instance of those objects. For example, when an intrusion detection system, specifically a CDS sensor, is detected on the network, an instance of a CDS  424  of FIG. 4 may be instantiated, which also corresponds to an analyzer  210  of FIG. 2. Models may interface with systems with different vendor proprietary software/equipment through the use of modular adaptors. Typically, an adaptor is software written to interact with a specific vendor proprietary software/equipment and the system. Adaptors usually take input from one application or network service and format the output in such a way that the target application will be able to understand it. An embodiment of the invention may use adaptors to aid in event collection for the building a topology for the network security domain. Adaptors parse information received from network devices to obtain information about the security topology. Such information includes the high-level information of FIG. 2 such as the reporting sensor  210 , the attack  230  type, attack source  240 , and the target host  240  and/or service  250  under attack. This information is used to create instances of specific objects described above in FIGS. 4 and 5. Once a topology is established, the present invention can then examine the connections and relationships of the instances to each other, and perform analysis to determine security root causes and impacts.  
         [0036]    3. Correlating Information in the Network Security Domain  
         [0037]    In the preferred embodiment, the network security fault analysis tool of the present invention uses the previously defined security topology to correlate information in the network security domain. The preferred embodiment uses SMARTS InCharge to generate a codebook of symptoms and problems which typically identifies which symptoms are caused by a particular problem by using the security topology based on the network security model. This codebook is an example of the causality matrix. The codebook is used for determining the root cause of any problem. The symptoms can be various events in the system. Problems are defined by a set of symptoms. After analyzing the symptoms, the present invention can ascertain the most likely problem or problems. This methodology is similar to that used in a medical diagnosis of a patient. Unlike a rule-based system, the present invention does not need an exact match or a complete set of information to determine a problem. Based on the known symptoms, the codebook can find the closest match and determine the problem. The present invention can be particularly useful in situations where a certain problem or an unrelated problem may block certain symptoms from being recognized. Although the preferred embodiment uses SMARTS Incharge codebook technology, the present invention could use any extendable CIM-based or other object-oriented fault analysis tool that allows faults and their associated events to be defined.  
         [0038]    Because the security model is generated independently of any specific topology, as events signal changes in the topology, the codebook can adapt, and the security model need not be changed. In conventional rule-based systems when the network changes, a system administrator usually has to change the rules and definitions whenever security devices are added or removed to maintain a properly functioning system. With the present invention, as the network changes, the network security system can automatically change the security topology and adapt the codebook accordingly because the security model can stay the same. In other words, because the security model does not change, devices of all types can be added or removed from the system as long as the device has been defined in the security model. The present invention would simply remove or add instances of already defined objects, and update their relationships to other objects in the topology.  
         [0039]    4. Cross-correlation of the Network Management and Network Security Domains  
         [0040]    The above explanation details the application of correlation technology to the single domain of network security. However, the present invention is capable of correlating across the domains of network management and network security. Preferably, the present invention would cross-correlate information in the security topology with physical machines and logical services in the network topology or vice versa. In the preferred embodiment, cross-correlation is the method by which the individual servers diagnose root causes for their specific domains, and the network security fault analysis tool (e.g. in the preferred embodiment, a higher level server) receives the input from both these domains and can produce the root cause based on that input for the total network picture. This mechanism allows operators to view root causes in the network as they affect their responsibilities. Thus, a particular operator can configure the present invention to automatically undertake a particular action or display the information she wanted whether it be only security, only network management, or a combination of both.  
         [0041]    [0041]FIG. 6 shows an embodiment of the interaction between domains in an embodiment of the present invention. Network correlation engine  610  (developed using conventional methods) manages network information about the system. Security correlation engine  620  (developed using the above disclosed description), manages security information about the system. Information from both engines are sent to the network security fault analysis tool  630  which can correlate the received information to provide a common operational picture of the entire network. While the network correlation engine  610  can operate independently from the security correlation engine  630  and vice versa, information from one engine can impact another. For example, if a security event is recorded, the network security fault analysis tool  630  can correlate that security event to a network event recorded at a similar time. The cross-correlation can aid an operator in more accurately diagnosing problems or assist in preventing future problems. The components of FIG. 6 are software programs that can be run on any server. Additionally, a large network could have multiple components running. If a company has multiple sites consisting of multiple subnets per site, each site could run its own network correlation engine  610  and security correlation engine  630 . Each site&#39;s engines would report to a single network security fault analysis tool  620  at the company&#39;s main network operations center (NOC). The NOC network security fault analysis tool  620  could then correlate and display a common operation picture  630  of all network security and management information across all of the company&#39;s sites.  
         [0042]    In addition to the ability to automatically cross-correlate the various domains to a common operational picture, the present invention allows an operator to view the complete picture of network and security status in a single location, as opposed to some conventional methods where an operator would have to monitor multiple screens and mentally put the picture together. For example, in a conventional system when a security alert occurs, the security operator may see the alert in the context of the security status of the network. If the alert impacts an operational asset (i.e., an attack disables a mail server), the network operators, in a conventional system, may see this as a result of the server being unavailable. In the preferred embodiment, an operator would automatically be presented with a combined picture, and be shown that there is a security event occurring, regardless of whether or not it impacts any operational assets. In addition, the operator can specify which type of information they would like to see, whether all of the available information or only a particular subset that is of interest to the operator. Because an operator may only be interested in some of the information in a system, the present invention can focus only on that information when cross-correlating, reducing the overhead.  
         [0043]    An embodiment of the present invention is shown in FIG. 7. System  700  comprises intrusion detection system  720  outside firewall  730 , intrusion detection system  740  inside firewall  730 , mail server  750 , mail server  760 , a network management station  770 , and network security fault analysis tool  790 . Attacker  710  resides somewhere outside system  700 . Attacker  710  sends a denial of service (DoS) attack to mail server  750  to disrupt the mail service. Intrusion detection system  720 , firewall  730 , and intrusion detection system  740  can detect the attack. If intrusion detection system  720  and intrusion detection system  740  both detect the attack, the present invention would then know that the firewall was unable to prevent attacker  710  from penetrating system  700 . Because the attack successfully traversed the firewall, it could disable mail server  750 . A successful attack on mail server  750  and the events leading to the attack would be reported and logged by network security fault analysis tool  790 .  
         [0044]    The security domain tools would be able to detect the attack on system  700  and the network management tools would be able to determine that mail server  750  is inoperable. Using the recorded events leading up to the attack (detected by intrusion detection systems  720  and  740  by attacker  710 , penetration through firewall  730  by attacker  710 , and the failed mail server  750  which was the target of attacker  710 ), the present invention can cross-correlate this information (e.g. the network management and security events) to determine that there was a DoS attack on a mail server. Using the network topology, the present invention can then determine if any other host, such as mail server  760  would be susceptible to the same or similar attack. For example, the network security fault analysis tool  780  may know that the mail server  750 , which resides inside of firewall  730 , was attacked and disabled by attacker  710 . Using this information (e.g. from the network security domain) and information about the network topology (e.g. from the network management domain), the network security fault analysis tool  780  can determine that there is another mail server in the network, i.e. mail server  760 , hosting the same software revisions, that also resides behind firewall  730  and that it would also likely be susceptible to an attack by attacker  710 . The present invention can then respond appropriately, for example, by notifying an operator of the problem and vulnerability of future attacks or triggering an automated response mechanism.  
         [0045]    With the present invention, events can be normalized because of the object-oriented nature of the network security and network management model and the use of sub-classes and inheritance. Normalizing events allows the present invention to identify the impact of those events on the entire managed network, not just their impact on a particular domain. For example, the conventional network management tool could log the activity shown in FIG. 7 as a failed mail server, and the security tool could log this activity as an attack. In the present invention, this activity would typically be logged as a single activity, e.g. a denial of service attack on a mail server, and the present invention could automatically provide the necessary information to a specific system function or an operator. Thus, the present invention is often more efficient than conventional security management tools because it can normalize attacks and other activity within the network. In some instances, such consolidation of information could lead the system or the operator to make proper adjustments to avoid similar problems in the future, whereas without cross-correlation of the information the operator might be unaware of a problem, the true cause of the problem, future risks, or a manner to correct the problem.  
         [0046]    Depending on the particular system or manager thereof, the present invention can be configured to recognize only particular events, devices or problems. Events, devices or problems may or may not be relevant, depending on the type of system or domains being monitored. Furthermore, an operator may wish to ignore certain events or problems. With the present invention, such information need not be analyzed. The present invention is dynamic and can be changed, in real-time if necessary, to accommodate many different implementations or changes thereto. Also, this flexibility can reduce the complexity, improve efficiency, and the overall speed of the system.  
         [0047]    Whereas the present invention has been described with respect to specific embodiments thereof, it will be understood that various changes and modifications will be suggested to one skilled in the art and it is intended that the invention encompass such changes and modifications as fall within the scope of the appended claims.