Abstract:
A method of managing alerts in a network including receiving alerts from network sensors, consolidating the alerts that are indicative of a common incident and generating output reflecting the consolidated alerts.

Description:
This application claims priority under 35 USC §120 to U.S. patent application Ser. No. 09/188,739, filed on Nov. 9, 1998, now U.S. Pat. No. 6,321,338, the entire contents of which are hereby incorporated by reference. 
    
    
     GOVERNMENT RIGHTS IN THIS INVENTION 
     This invention was made with U.S. government support under contract numbers F30601-96-C-0294 and F30602-99-C-0187 awarded by the U.S. Air Force Research Laboratory. The U.S. government has certain rights in this invention. 
    
    
     TECHNICAL FIELD 
     This invention relates to network-based alert management. 
     BACKGROUND 
     Computer networks may include one or more digital security monitors or sensors that automatically analyze traffic on the network to identify potentially suspicious activity. The sensors may be implemented in either software or hardware. Monitors may focus on security monitoring and/or on fault analysis. 
     Upon detecting suspicious activity, the sensors typically generate some kind of digital alert message or signal, and attempt to bring that message to the attention of network I/S managers whose responsibility it is to respond and react in an appropriate defensive manner against hostile digital attacks or to recover quickly from catastrophic failures. 
     SUMMARY 
     In an aspect, the invention features a method of managing alerts in a network including receiving alerts from network sensors, consolidating the alerts that are indicative of a common incident and generating output reflecting the consolidated alerts. Alerts are formatted into a standard alert format by the network sensors or an input receiving logic of an alert management system, or a combination of both. The alert format may be selected from a group of formats including IDIP, SNMP, HP OpenView, Attach Specification CIDF and GIDO. Alerts may be tagged with corresponding significance scores where the significance scores may include a priority measure for the corresponding alerts. The priority measure may be derived from a priority map that can be automatically generated or dynamically adjusted. The priority map may contain relative priority scores for resource availability, resource integrity and resource confidentiality. 
     In another aspect, the invention features a method of managing alerts including receiving alerts from a number of network sensors, filtering the alerts to produce one or more internal reports and consolidating the internal reports that are indicative of a common incident-to-incident report. Related incident reports may be correlated. The network sensors may format the received alerts. Filtering includes deleting alerts that do not match specified rules. The filtering rules may be dynamically adjusted. Filtering may also include tagging alerts with a significance score that can indicate a priority measure and relevance measure. 
     Among the advantages of the invention may be one or more of the following. 
     The alert manager can be tailored to a particular application by dynamically adding or removing data connections to sources of incoming alerts, and by dynamically varying the process modules, user filter clauses, priority clauses, topology clauses, and output. Process modules may be added, modified, and deleted while the alert manager is active. Output may be configured for a variety of graphical user interfaces (GUIs). In embodiments, useful, for example, for each category of attack the user can define different priorities as related to denial of service, security, and integrity. 
     Process modules are logical entities within the alert manager that can respond to an incoming alert in real time and virtual time, i.e., data within an application can cause the alert manager to respond. 
     The alert manager can act as a sender or receiver. In embodiments, useful, for example, the alert manager can listen to a specific port in a network or connect to an external process on a host computer and process its data. 
     The alert management process can be an interpretive process allowing the incorporation of new process clauses and new rules. 
     The alert management process may provide a full solution for managing a diverse suite of multiparty security and fault monitoring services. Example targets of the alert management process are heterogeneous network computing environments that are subject to some perceived operational requirements for confidentiality, integrity, or availability. Inserted within the network are a suite of potential multiparty security and fault monitoring services such as intrusion detection systems, firewalls, security scanners, virus protection software, network management probes, load balancers, or network service appliances. The alert management process provides alert distributions within the monitored network through which security alerts, fault reports, and performance logs may be collected, processed and distributed to remote processing stations (e.g., Security Data Centers, Administrative Help Desks, MIS stations). Combined data produced by the security, fault, or performance monitoring services provide these remote processing stations detailed insight into the security posture, and more broadly the overall health, of the monitored network. 
     Value may be added to the content delivered by the alert management process to the remote processing station(s) that subscribe to alerts in the form of an advanced alert processing chain. For example, alerts received by the alert management process and prepared for forwarding to a remote processing station, may be filtered using a dynamically downloadable message criteria specification. 
     In a further aspect, alerts may be tagged with a priority indication flag formulated against the remote processing station&#39;s alert processing policy and tagged with a relevance flag that indicates the likely severity of the attack with respect to the known internal topology of the monitored network. 
     In a further aspect of the invention, alerts may be aggregated (or consolidated) into single incident reports when found to be associated with a series of equivalent alerts produced by the same sensor or by other sensors, based upon equivalence criteria, and the incident reports forwarded to the remote processing station. 
     The alert management system is configurable with respect to the data needs and policies specified by the remote processing station. These processes are customizable on a per remote processing station basis. For example, two remote processing stations may in parallel subscribe to alerts from the alert management process, with each having individual filtering policies, prioritization schemes, and so forth, applied to the alert/incident reports it receives. 
     Other features and advantages will become apparent from the following description and from the claims. 
    
    
     DESCRIPTION OF DRAWINGS 
     FIG. 1 is a block diagram of a network based alert management system. 
     FIG. 2 is a flow diagram of an alert management process. 
     FIG. 3 is a block diagram of a priority database record. 
     FIG. 4 is a block diagram of the remote processing center. 
     FIG. 5 is a block diagram of a software architecture for the alert management system. 
     FIG. 6 is a block diagram of a computer platform. 
    
    
     Like reference symbols in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     Referring to FIG. 1, a network based alert management system  10  includes a network  12 , a network  14 , and a network  16 . Each of the networks  12 - 14  includes a number of computer systems collectively labeled  18 , interconnected, for example, by an Ethernet cable  20 . Each of the networks  12 - 14  includes security and fault monitoring systems generally labeled  22 . Each security and fault monitoring system  22  is linked to an alert manager  24 . The alert manager  24  is linked to one or more remote processing centers generally labeled  26 . Each alert processing center  26  includes a remote management interface  36  (shown on only one center  26  by way of example). The remote management interface  36  provides a user (not shown) the capability of configuring reports produced by the alert manager  24 . 
     The security and fault monitoring systems  22  may include, for example, intrusion detection systems, firewalls, security scanners, virus protection software, network management probes, load balancers, and network service appliances. Each of the security and fault monitoring systems  22  produces an alert stream in the form of, for example, security alerts, fault reports, and performance logs. The alert stream is sent to the alert manager  24  for collection, processing, and distribution to the remote processing center  26 . Example remote processing centers  26  are security data centers, administrative help desks, and MIS stations. 
     In an embodiment, the remote processing center  26  subscribes to the alert manager  24  which in turns distributes specific collected and processed alert information to the remote processing center  26 , more fully described below. 
     The networks  14 ,  14 , and  16  being monitored by the security and fault monitoring systems  22  may include any computer network environment and topology such as local area networks (LAN), wide area networks (WAN), Ethernet, switched, and TCP/IP-based network environments. Network services occurring within the networks  12 - 16  include features common to many network operating systems such as mail, HTTP, ftp, remote log in, network file systems, finger, Kerbebos, and SNMP. Each of the sensors  22  monitors various host and/or network activity within the networks  12 - 16 , and each sensor  22 , as discussed above, generate a stream of alerts, triggered by potentially suspicious events, such as network packet data transfer commands, data transfer errors, network packet data transfer volume, and so forth. The alerts indicate a suspicion of possible malicious intrusion or other threat to operations within the networks  12 - 16 . 
     The alert manager  24  includes a receive-input logic module  28 . In an embodiment, the receive-input logic  28  of the alert manager  24  subscribes, i.e., establishes a transport connection, to receive each of the alert streams produced by the sensors  22  through a secure electronic communication line (SSL)  30 . The alert streams contain raw, i.e., unprocessed, alerts. The monitors  22  may format their respective alert streams in a variety of formats, such as IDIP, SNMP, HP Openview, an XML-based standard format (such as the Attack Specifications from IETF), Common Intrusion Detection Framework (CIDF), GIDOs, or some other format. The receive-input logic  28  of the alert manager  24  is equipped with translation modules  32  to translate the original, raw alert streams from the monitors  22  into a common format for further processing, if the alerts do not arrive in the common format. 
     In another embodiment, the monitors  22  include conversion software (not shown), also referred to as “wrapper” software that translates a monitor&#39;s raw alert stream into the common format used by the alert manager  24 . The wrapper software can add data items of interest to the alert manager  24 , by querying its network  12 - 16 . 
     In another embodiment, a combination of monitors  22  having wrapper software and the receive-input logic  28  preprocessing raw alerts in the alert management network  10  are present to accommodate a heterogeneous base of monitors  22  that an end-user desires to manage. 
     The alert manager  24  includes an alert processing engine  34 . Raw alerts received by the receive-input module  28  and formatted into the common format are sent to the alert processing engine  34 . 
     Referring to FIG. 2, an alert management process  50  residing in the alert processing engine  34  includes receiving  52  formatted alerts from the receive-input logic  28 . The formatted alerts are passed  54  through user-specified filters and alerts not matching criteria of the user-specified filters are discarded. 
     For example, a particular end-user subscriber may be responsible only for a portion of the overall operations network and may only wish to see alerts coming from a particular subset of monitors  22 , e.g., from particular ports. Each end-user subscriber can interactively define his or her own customized user-specified filters using the remote management interface  36  of the remote processing center  26 , fully described below. 
     The filtered alerts are prioritized  56 , i.e., rated or scored according to priorities dynamically controlled by the user. In an embodiment, the priority of an alert is determined by analyzing the known, (relative) potential impact of the attack category identified with respect to each of various concerns such as confidentiality, data integrity, and system availability. Confidentiality involves allowing only authorized users to view network data. Data integrity involves allowing only authorized persons to change data. System availability involves providing users access to data whenever needed with minimum downtime. 
     Different categories of known computer intrusions and anomalies generally pose threats with differing levels of impact on each of the above three concerns. In addition, for different users and different applications, each of the concerns may be of different relative priority. For example, in a general Internet news/search portal like Yahoo! or Lycos, continuous availability may be a more important concern than confidentiality. Conversely, for a government intelligence database, confidentiality may be a greater priority than continuous availability. For an e-commerce business site, all three concerns may be of roughly equal seriousness and priority. An ultimate priority score assigned to a particular alert for a given end-user during prioritization  56  reflects a sum or combination of the identified attack&#39;s potential adverse impact along each of the dimensions of interest (confidentiality, data integrity, and system availability), weighted by the end-user&#39;s individual profile of relative priority for each such dimension. 
     In an embodiment, a default priority profile is provided for each user or subscriber that assigns equal priority to confidentiality, data integrity, and system availability. In a preferred embodiment, the end-user may configure the priorities dynamically, and modify the default values as desired, through the remote management interface  36  that gives the user the flexibility to customize priority assignments in a manner that reflects his/her unique concerns. 
     In an another embodiment, users (or system developers) directly assign a relative priority score to each type of attack, instead of ranking more abstract properties such as integrity or availability, that allows more precise reflection of a user&#39;s priorities regarding specific attacks, but requires more initial entry of detailed information. 
     In an embodiment, users may register a listing of critical services, identified by &lt;host ID, protocol&gt; pairs, as to whom potential attacks or operational failures are considered to be of especially high priority. 
     Management and alteration of filters and listings of critical services in accordance with each of the prioritization methodologies described above can are performed dynamically and interactively while alert manager  24  is in operation and as user priorities change using the remote management interface  36 . 
     The alerts are topology vetted  58 . Vetting  58  provides a relevance rating to alerts based on the topological vulnerability of the network being monitored to the type of attack signaled by the alert. Example topologies include the computing environment, what kind of operating system (O/S), network infrastructure, and so forth. In a preferred embodiment, vetting  58  utilizes a mapping between each network host and an enumeration of that host&#39;s O/S and O/S version(s). Vetting step  58  further preferably utilizes a topology relevance table indicating the relevance of various types of attacks to each of the different possible OS/version environments. Thus, to determine and assign a relevance score for a particular alert, the host ID (hostname/IP address) for the target of that alert can be used to retrieve its OS/version information, and the OS/version along with the attack type of the alert can be used to retrieve a relevancy score from the topology table. 
     In an embodiment, the topology table of the network being monitored is dynamically configurable by end users through the remote management interface  36 . 
     In another embodiment, automatic local area network (LAN) mapping is provided by a network topology scope application. 
     The relevance of various types of known attacks against different topologies is preferably specified in predefined maps, but dynamically configured using the remote management interface  36 . 
     Internal reports are generated  60  from the output of filtering  54 , prioritizing  56  and vetting  58 . Internal reports generally include fewer alerts as compared with the original raw alert stream, as a result of the user-configured filtering  40 . Internal reports also tag or associate each alert with priority and/or relevance scores as a result of priority mapping  56  and topology vetting  58 , respectively. 
     The internal reports are used to generate  62  consolidated incident reports. A consolidated incident report adds perspective and reduces information clutter by merging/combining the internal reports for multiple alerts into a single incident report. In a preferred embodiment, generating  62  is carried out through report aggregation and equivalence recognition. Aggregation refers to combining alerts produced by a single sensor, whereas equivalence recognition refers to combining alerts from multiple sensors. 
     The underlying notion in both cases is that nominally different alerts may actually represent a single intrusion “incident” in the real world. By analogy, a single criminal intrusion into a physical property might trigger alarms on multiple sensors such as a door alarm and a motion detector that are instrumented on the same premises, but from an informational perspective both alarms are essentially signaling the same event. 
     In an embodiment, alert parameters examined for report aggregation include a variable combination of attack type, timestamp, monitor identification (ID), user ID, process ID, and &lt;IP, port addresses&gt; for the source and target of the suspicious activity. 
     When an internal report is generated  60  alerts are consolidated and the corresponding priority and relevance tags for the individual alerts are merged into single meta-priority/meta-relevance scores for the single incident. Different functions may be utilized for doing the priority blend, such as additive, min/max, average, and so forth. Duration of the overall incident is also preferably computed and associated with the incident, based on the time stamps of the various individual alerts involving the incident. 
     The consolidated incident reports are used to generate  64  a report output. Formatting of the output report is based on subscriber-customized criteria that are defined using the remote management interface  36 . The report output is transported  66  to the remote processing center  26 . 
     Selection of a transport is under user control and managed using the remote management interface  36 . The user may specify, for example, E-mail, XML, HTML and/or writing out to a file. In an embodiment, the transport occurs over an SSL for display and assessment by the end-user. 
     The filtering  54 , prioritization  54  and topology vetting  58  are event driven, i.e., each alert is processed and filtered/tagged as it arrives, one alert at a time. However, temporal clauses are utilized for aspects of report aggregation and equivalence recognition among multiple alerts. For example, as internal reports are generated  60  a sliding window is established during which additional records may be merged into the aggregate incident report. A single-alert internal report may be sent to the remote processing center  26  indicating that it has witnessed the alert. A subsequent aggregate alert report, i.e., an incident report, covering that single alert as well as others, may also be forwarded to the remote processing center  26  to indicate a duration of the attack/incident, an aggregate count of individual alerts representing this incident, and an aggregate priority. In an embodiment, aggregate alert flushing may occur after some period of inactivity (e.g., “two minutes since last event”). The aggregate alert flushing is not event driven, but rather driven by an internal timeout recognized from a system clock (not shown) of the alert manager  24 . 
     Referring to FIG. 3, an exemplary priority database record  80  used for prioritization  56  of filtered alerts includes example network attacks ping of death  82 , buffer overflow  84  and write polling violation  86 . For each of the attacks  82 - 86 , a relative priority rating is assigned, namely, denial of service (system availability)  88 , data integrity  90 , and security (confidentiality)  92 . By way of example, a first end-user  94  weights denial of service at 0%, data integrity at 20%, and security at 80%. A second end-user  96  weights denial of service at 80%, data integrity at 10% and security at 10%. Thus, for the priority database record  80 , the user  94  emphasizes a high concern (priority) with security, while the user  96  emphasizes a high concern (priority) with denial of service. 
     In this example, for first user  94  a “ping of death” alert  82  will have a priority score=(0*90)+(0.2*10)+(0.8*10)=10; whereas for second user  96  a “ping of death” alert  82  will receive a priority score=(0.8*90)+(0.1*10)+(0.1*10)=74. 
     As is seen from the description above, (a) it is the relative value of these priority scores that has significance, not the absolute magnitudes, and (b) the priority values for alerts and for user preferences are subjective values that may vary from one application to another and from one user to another. As noted above, the alert priority map values and user priority profiles may be dynamically adjusted and customized by individual users via remote management interface  36 . 
     Referring again to FIG. 1, the report output of the alert processing process  50  is stored at the remote processing center  26  in a database  38  contained in a storage device  40  for retrieval and reporting by the end user. In an embodiment, the report output is translated at the remote processing center  26  in accordance with a user-configurable database schema into an existing/legacy database management system (not shown) contained in the remote processing center  26  for convenience of the end-user, either manually by a database integration team or automatically using a database mediator/translator. The remote management interface  36  accesses the database management system and presents the report output to the end-user, such as by a graphical user interface (GUI) on a workstation  42 . 
     In an embodiment, the alert management network  10  provides an open, dynamic infrastructure for alert processing and management. The alert manager  24  preferably includes functionality for dynamically generating, suspending, and configuring data connections and logical process modules, in response to interactive remote user commands issued via remote management interface  36 . The remote management interface  36  preferably executes a java application that generates command files, in response to end user requests, in the form of directives and any necessary data files, such as the priority database record  80 , and so forth. The java application communicates, e.g. via telnet, to the alert manager  24  and downloads the directives and data files. The alert processing engine  34 , preferably a postscript interpreter in one embodiment, can process the directives dynamically. Many of the directives are preferably defined in terms of postscript code that resides locally in a library  44  in the alert manager  24 . Applications running in alert manager  24  are written in modular fashion, allowing directives to accomplish meaningful change of logical behavior by instructing the alert manager  24  to terminate a particular process clause and activate a newly downloaded clause, for example. 
     By way of another example, through the operation of the alert processing engine  34  the alert manager  24  can dynamically establish and suspend connections to the various alert streams generated by the security and fault monitoring systems  22 . Thus, the alert manager  24  can dynamically “plug into” (i.e., connect) new alert streams, such as alert streams from additional sensors newly deployed by an end-user, and likewise can dynamically suspend (permanently or temporarily) its connection to alert streams from sensors  22  that are removed, replaced, taken offline, and so forth. Similarly, alert manager  24  can dynamically generate or suspend modules of the alert management process  50 , and can dynamically adjust the configurable parameter settings of those modules. 
     In this manner, alert manager  24  is designed to be responsive to dynamic configuration requests initiated by end users using the remote management interface  36  of the remote processing center  26 . As mentioned above, the remote management interface  36  provides an interactive interface at workstation  42  for end-users to specify desired modifications to the dynamically configurable aspects of alert manager  24 . 
     Referring to FIG. 4, a block diagram of a software architecture  100  for a dynamic, open, alert management infrastructure in accordance with preferred embodiments of the present invention is shown. An infrastructure module  102  (labeled “eFlowgen”) provides core infrastructure functionality, including implementation of the alert processing engine  34 , and need not be specialized to alert management applications. An inline application code module  104  (in conjunction with an initialization module  106 , described below) defines an alert management application, including the overall alert analysis and reporting process  50  described above with reference to FIG.  2 . Initialization script module  106  complements application code module  104 , by defining, for a particular application instance, the specifics of the input/output transport connections and specifics of the logical alert processing clauses corresponding to the process  50 . A dynamic definitions module  108  represents dynamic changes submitted by users via the remote management interface  36 , such as configuration changes and other extensions as previously discussed; the functionally dynamic definitions module  180  are comparable to initialization script module  106 , except for being dynamically submitted and incorporated into the running application. 
     A detailed functional specification for a software infrastructure corresponding to eFlowgen module  102  is included in the Appendix, incorporated herein. 
     In another embodiment, referring to FIG. 5, the remote processing center  26  includes a correlation logic engine  110 . The correlation logic engine  110  accesses and compares incident reports in database  38  and attempts to provide intelligent assistance to end-users in the analytical task of discovering patterns and making sense of alert data. The correlation engine logic  110  looks for key attribute relations in common for different incidents, such as incidents targeting a single host machine over a relatively short time frame, or incidents reflecting attacks or anomalies coming from a particular source machine. Automatically correlating separate incidents helps end-users recognize more quickly that a particular machine is under serious attack or that some other machine is a hostile “bad guy,” for example, and the end-users can then take appropriate defensive action. 
     Another correlation technique residing in the correlation logic engine  110  looks for interrelated vulnerabilities, applying rule-based knowledge to look for groups of distinct incidents that can inferentially be interpreted as related parts of a single, coordinated attack. For example, rules matching patterns of incidents that look like a chain over time, where the target of an earlier incident becomes the source of a subsequent incident, may allow correlation logic engine  110  to conclude that these likely are not unrelated incidents, and that a “worm” infection appears to be spreading. 
     In an embodiment, the correlation logic engine  110  incorporates statistical inferential methods. The correlation logic engine  110  attempts to draw conclusions automatically based on received intrusion incident reports. The correlation logic engine  110  produces reports for the end-user indicating correlation found. 
     The alert manager  24  and other components of the alert management network  10  may be implemented and executed on a wide variety of digital computing platforms, including, but not limited to, workstation-class computer hardware and operating system software platforms such as Linux, Solaris, FreeBSD/Unix, and Windows-NT. 
     Referring to FIG. 6, a computer platform  120  suitable for hosting and executing the alert management process  50  includes a display device  122  connected to a computer  124 . The computer  124  includes at least a memory  126  and a central processing unit (CPU)  128 . The computer  124  includes a link to a storage device  130  and a network link  132 . 
     The storage device  130  can store instructions that form an alert manager  24 . The instructions may be transferred to the memory  126  and CPU  128  in the course of operation. The instructions for alert manager  24  can cause the display device  122  to display messages through an interface such as a graphical user interface (GUI). Further, instructions may be stored on a variety of mass storage devices (not shown). 
     Other embodiments are within the scope of the following claims.