%0 Journal Article %T The Use of Artificial-Intelligence-Based Ensembles for Intrusion Detection: A Review %A Gulshan Kumar %A Krishan Kumar %J Applied Computational Intelligence and Soft Computing %D 2012 %I Hindawi Publishing Corporation %R 10.1155/2012/850160 %X In supervised learning-based classification, ensembles have been successfully employed to different application domains. In the literature, many researchers have proposed different ensembles by considering different combination methods, training datasets, base classifiers, and many other factors. Artificial-intelligence-(AI-) based techniques play prominent role in development of ensemble for intrusion detection (ID) and have many benefits over other techniques. However, there is no comprehensive review of ensembles in general and AI-based ensembles for ID to examine and understand their current research status to solve the ID problem. Here, an updated review of ensembles and their taxonomies has been presented in general. The paper also presents the updated review of various AI-based ensembles for ID (in particular) during last decade. The related studies of AI-based ensembles are compared by set of evaluation metrics driven from (1) architecture & approach followed; (2) different methods utilized in different phases of ensemble learning; (3) other measures used to evaluate classification performance of the ensembles. The paper also provides the future directions of the research in this area. The paper will help the better understanding of different directions in which research of ensembles has been done in general and specifically: field of intrusion detection systems (IDSs). 1. Introduction The threat of Internet attacks is quite real and frequent so this has increased a need for securing information on any network on the Internet. The objective of information security includes confidentiality, authentication, integrity, availability, and nonrepudiation [1]. The set of activities that violates security objectives is called intrusion. Thus secure information requires the phases that provide (1) protection: automatic protection from intrusions; (2) detection: automatic detection of intrusions; (3) reaction: automatic reaction or alarm when system is intruded; (4) recovery: repair or recovery of loss caused due to intrusion [2]. Out of these phases, the perfect detection of an intrusion is the most important. As only after correct detection of intrusion, correct reaction and recovery phase of information security can be implemented. In the literature, many IDSs have been developed implementing various techniques from different disciplines like statistical techniques, AI techniques, and so forth. Some IDSs have been developed based on single-classification technique while other IDSs (called hybrid/ensemble IDS) implement more-than-one-classfication %U http://www.hindawi.com/journals/acisc/2012/850160/