With the growing deployment of host and network intrusion detection systems, managing reports from these systems becomes critically important. We present a probabilistic approach to alert correlation, extending ideas from multisensor data fusion. Features used for alert correlation are based on alert content that anticipates evolving IETF standards. The probabilistic approach provides a unified mathematical framework for correlating alerts that match closely but not perfectly, where the minimum degree of match required to fuse alerts is controlled by a single configurable parameter. Only features in common are considered in the fusion algorithm. For each feature we define an appropriate similarity function. The overall similarity is weighted by a specifiable expectation of similarity. In addition, a minimum similarity may be specified for some or all features. Features in this set must match at least as well as the minimum similarity specification in order to combine alerts, regardless of the goodness of match on the feature set as a whole. Our approach correlates attacks over time, correlates reports from heterogeneous sensors, and correlates multiple attack steps.

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Probabilistic Alert Correlation

A computer-implemented intrusion detection system and method that monitors a computer system in real-time for activity indicative of attempted or actual access by unauthorized persons or computers. The system detects unauthorized users attempting to enter into a computer system by comparing user behavior to a user profile, detects events that indicate an unauthorized entry into the computer system, notifies a control function about the unauthorized users and events that indicate unauthorized entry into the computer system and has a control function that automatically takes action in response to the event. The user profiles are dynamically constructed for each computer user when the computer user first attempts to log into the computer system and upon subsequent logins, the user's profile is dynamically updated. By comparing user behavior to the dynamically built user profile, false alarms are reduced. The system also includes a log auditing function, a port scan detector and a session monitor function.

Intrusion detection system

A method of describing intrusion signatures, which are used by an intrusion detection system to detect attacks on a local network. The signatures are described using a “high level” syntax having features in common with regular expression and logical expression methodology. These high level signatures may then be compiled, or otherwise analyzed, to provide a process executable by a sensor or other processor-based signature detector.

Intrusion detection signature analysis using regular expressions and logical operators

A security management system includes a fusion engine which “fuses” or assembles information from multiple data sources and analyzes this information in order to detect relationships between raw events that may indicate malicious behavior and to provide an organized presentation of information to consoles without slowing down the processing performed by the data sources. The multiple data sources can comprise sensors or detectors that monitor network traffic or individual computers or both. The sensors can comprise devices that may be used in intrusion detection systems (IDS). The data sources can also comprise firewalls, audit systems, and other like security or IDS devices that monitor data traffic in real-time. The present invention can identify relationships between one or more real-time, raw computer events as they are received in real-time. The fusion engine can also assess and rank the risk of real-time raw events as well as mature correlation events.

Method and System for Managing Computer Security Information

An improved computer network security system and method wherein access to network resources is based on information that includes the location of the connecting user. In general, the less trusted the location of the user, the more the access rights assigned to the user are restricted. A discrimination mechanism and process determines the location of a user with respect to categories of a security policy, such as to distinguish local users, intranet users and dial-up users from one another. Based on information including the location and the user's credentials, an access token is set up that may restrict the user's normal access in accordance with the security policy, such as to not restrict a user's processes beyond the user-based security information in the user's normal access token, while further restricting the same user's access to resources when connecting via a dial-up connection. Restricted tokens are preferably used to implement the location-based discrimination by restricting the security context of users connecting from less trusted locations.

Method and system of security location discrimination

In one embodiment, local software code present in a computer system enables real-time detection of whether the computer system is properly protected against malicious attacks from harmful software. For example, software code such as one or more agents executing in the computer system support real-time protection validation based upon detection of the behavior of the computer system (as opposed to mere detection of the presence of resources or applications in the computer system). In response to detecting that the computer system or an application accesses or provides a particular type of resource and should be protected via one or more appropriate protection policies, if the computer system is not already protected, an agent of the computer system can provide immediate remediation (e.g., a security measure) to temporarily protect the computer system until the appropriate protection policy can be activated to protect the computer system against malicious software threats.

Protection of computer resources

A system provides security to a computerized device by detecting a sequence of related processing operations within the computerized device and recording the sequence of related processing operations in a security history. The system identifies a security violation when a processing operation performed in the computerized device produces an undesired processing outcome that violates a security policy and subsequently detecting attempted performance of at least one processing operation that attempts to produce the undesired processing outcome that violates the security policy and in response, denies operation of the processing operation(s) within the computerized device to avoid violation of the security policy.

Methods and apparatus providing security to computer systems and networks

The invention features receiving encrypted network packets sent over a network (20) at a network interface computer (16) and passing the encrypted network packets to a computer (18) on an internal network. The invention further features receiving network packets sent over a network (20), determining which virtual tunnel (140, 142) each network packet was sent over, and routing each network packet to a destination computer in accordance with the determined virtual tunnel (140, 142).

Transferring encrypted packets over a public network

A system controls security during operation of a computerized device byenforcing a first security policy during first operational state of the computerized device. Enforcement of the first security policy provides a first level access to resources within the computerized device by processes operating in the computerized device. The system detects a transition operation of the computerized device that occurs during enforcement of the first security policy indicating that operation of the computerized device is transitioning from the first operational state to a second operational state and in response, enforces a second security policy corresponding to the second operational state to provide a level of access to the resources within the computerized device that corresponds to the second operational state during operation of the second operational state. This can be repeated for many different states including boot time, normal runtime, installation, shutdown, and a compromised state.

Methods and apparatus providing security for multiple operational states of a computerized device

A Stateful Reference Monitor can be loaded into an existing commercial operating system, and then can regulate access to many different types of resources. The reference monitor maintains an updateable storage area whose contents can be used to affect access decisions, and access decisions can be based on arbitrary properties of the request.

Jeffrey A. Kraemer

Papers

Protection of computer resources

Methods and apparatus providing security to computer systems and networks

Transferring encrypted packets over a public network

Methods and apparatus providing security for multiple operational states of a computerized device

Stateful reference monitor