Karl Levitt

Bio: Karl Levitt is an academic researcher from University of California, Davis. The author has contributed to research in topics: Intrusion detection system & HOL. The author has an hindex of 34, co-authored 120 publications receiving 6192 citations. Previous affiliations of Karl Levitt include University of Stavanger & University of California.

Network intrusion detection

Abstract: Intrusion detection is a new, retrofit approach for providing a sense of security in existing computers and data networks, while allowing them to operate in their current "open" mode. The goal of intrusion detection is to identify unauthorized use, misuse, and abuse of computer systems by both system insiders and external penetrators. The intrusion detection problem is becoming a challenging task due to the proliferation of heterogeneous computer networks since the increased connectivity of computer systems gives greater access to outsiders and makes it easier for intruders to avoid identification. Intrusion detection systems (IDSs) are based on the beliefs that an intruder's behavior will be noticeably different from that of a legitimate user and that many unauthorized actions are detectable. Typically, IDSs employ statistical anomaly and rulebased misuse models in order to detect intrusions. A number of prototype IDSs have been developed at several institutions, and some of them have also been deployed on an experimental basis in operational systems. In the present paper, several host-based and network-based IDSs are surveyed, and the characteristics of the corresponding systems are identified. The host-based systems employ the host operating system's audit trails as the main source of input to detect intrusive activity, while most of the network-based IDSs build their detection mechanism on monitored network traffic, and some employ host audit trails as well. An outline of a statistical anomaly detection algorithm employed in a typical IDS is also included. >

DIDS (distributed intrusion detection system)—motivation, architecture, and an early prototype

Abstract: Intrusion detection is the problem of identifying unauthorized use, misuse, and abuse of computer systems by both system insiders and external penetrators. The proliferation of heterogeneous computer networks provides additional implications for the intrusion detection problem. Namely, the increased connectivity of computer systems gives greater access to outsiders, and makes it easier for intruders to avoid detection. IDS’s are based on the belief that an intruder’s behavior will be noticeably different from that of a legitimate user. We are designing and implementing a prototype Distributed Intrusion Detection System (DIDS) that combines distributed monitoring and data reduction (through individual host and LAN monitors) with centralized data analysis (through the DIDS director) to monitor a heterogeneous network of computers. This approach is unique among current IDS’s. A main problem considered in this paper is the Network-user Identification problem, which is concerned with tracking a user moving across the network, possibly with a new user-id on each computer. Initial system prototypes have provided quite favorable results on this problem and the detection of attacks on a network. This paper provides an overview of the motivation behind DIDS, the system architecture and capabilities, and a discussion of the early prototype.

A network security monitor

Abstract: This study concentrates on the security-related issues in a single broadcast LAN (local area network) such as Ethernet. The authors formalize various possible network attacks. Their basic strategy is to develop profiles of usage of network resources and then compare current usage patterns with the historical profile to determine possible security violations. Thus, the work is similar to the host-based intrusion-detection systems. Different from such systems, however, is the use of a hierarchical model to refine the focus of the intrusion-detection mechanism. The authors also report on the development of an experimental LAN monitor currently under implementation. Several network attacks have been simulated, and results on how the monitor has been able to detect these attacks are analyzed. Initial results demonstrate that many network attacks are detectable with the authors' monitor, although it can be defeated. >

A requires/provides model for computer attacks

Abstract: Computer attacks are typically described in terms of a single exploited vulnerability or as a signature composed of a specific sequence of events. These approaches lack the ability to characterize complex scenarios or to generalize to unknown attacks. Rather than think of attacks as a series of events, we view attacks as a set of capabilities that provide support for abstract attack concepts that in turn provide new capabilities to support other concepts. This paper describes a flexible extensible model for computer attacks, a language for specifying the model, and how it can be used in security applications such as vulnerability analysis, intrusion detection and attack generation

Execution monitoring of security-critical programs in distributed systems: a specification-based approach

Abstract: We describe a specification-based approach to detect exploitations of vulnerabilities in security-critical programs. The approach utilizes security specifications that describe the intended behavior of programs and scans audit trails for operations that are in violation of the specifications. We developed a formal framework for specifying the security-relevant behavior of programs, on which we based the design and implementation of a real-time intrusion detection system for a distributed system. Also, we wrote security specifications for 15 Unix setuid root programs. Our system detects attacks caused by monitored programs, including security violations caused by improper synchronization in distributed programs. Our approach encompasses attacks that exploit previously unknown vulnerabilities in security-critical programs.

Bro: a system for detecting network intruders in real-time

Abstract: We describe Bro, a stand-alone system for detecting network intruders in real-time by passively monitoring a network link over which the intruder's traffic transits. We give an overview of the system's design, which emphasizes high-speed (FDDI-rate) monitoring, real-time notification, clear separation between mechanism and policy, and extensibility. To achieve these ends, Bro is divided into an "event engine" that reduces a kernel-filtered network traffic stream into a series of higher-level events, and a "policy script interpreter" that interprets event handlers written in a specialized language used to express a site's security policy. Event handlers can update state information, synthesize new events, record information to disk, and generate real-time notifications via syslog. We also discuss a number of attacks that attempt to subvert passive monitoring systems and defenses against these, and give particulars of how Bro analyzes the four applications integrated into it so far: Finger, FTP, Portmapper and Telnet. The system is publicly available in source code form.

A sense of self for Unix processes

Abstract: A method for anomaly detection is introduced in which ``normal'' is defined by short-range correlations in a process' system calls. Initial experiments suggest that the definition is stable during normal behavior for standard UNIX programs. Further, it is able to detect several common intrusions involving sendmail and lpr. This work is part of a research program aimed at building computer security systems that incorporate the mechanisms and algorithms used by natural immune systems.

Ariadne: a secure on-demand routing protocol for ad hoc networks

Abstract: An ad hoc network is a group of wireless mobile computers (or nodes), in which individual nodes cooperate by forwarding packets for each other to allow nodes to communicate beyond direct wireless transmission range. Prior research in ad hoc networking has generally studied the routing problem in a non-adversarial setting, assuming a trusted environment. In this paper, we present attacks against routing in ad hoc networks, and we present the design and performance evaluation of a new secure on-demand ad hoc network routing protocol, called Ariadne. Ariadne prevents attackers or compromised nodes from tampering with uncompromised routes consisting of uncompromised nodes, and also prevents a large number of types of Denial-of-Service attacks. In addition, Ariadne is efficient, using only highly efficient symmetric cryptographic primitives.

Denial of service in sensor networks

Abstract: Sensor networks hold the promise of facilitating large-scale, real-time data processing in complex environments, helping to protect and monitor military, environmental, safety-critical, or domestic infrastructures and resources, Denial-of-service attacks against such networks, however, may permit real world damage to public health and safety Without proper security mechanisms, networks will be confined to limited, controlled environments, negating much of the promise they hold The limited ability of individual sensor nodes to thwart failure or attack makes ensuring network availability more difficult To identify denial-of-service vulnerabilities, the authors analyzed two effective sensor network protocols that did not initially consider security These examples demonstrate that consideration of security at design time is the best way to ensure successful network deployment