The increasing practicality of large-scale flow capture makes it possible to conceive of traffic analysis methods that detect and identify a large and diverse set of anomalies. However the challenge of effectively analyzing this massive data source for anomaly diagnosis is as yet unmet. We argue that the distributions of packet features (IP addresses and ports) observed in flow traces reveals both the presence and the structure of a wide range of anomalies. Using entropy as a summarization tool, we show that the analysis of feature distributions leads to significant advances on two fronts: (1) it enables highly sensitive detection of a wide range of anomalies, augmenting detections by volume-based methods, and (2) it enables automatic classification of anomalies via unsupervised learning. We show that using feature distributions, anomalies naturally fall into distinct and meaningful clusters. These clusters can be used to automatically classify anomalies and to uncover new anomaly types. We validate our claims on data from two backbone networks (Abilene and Géant) and conclude that feature distributions show promise as a key element of a fairly general network anomaly diagnosis framework.

Abstract—As a use of network increases for critical transaction, so huge damages are caused by intrusion attacks hence there is the need of Computer network security. To protect network against various active and passive attack, various technique have been suggested.Traditional methods depends on specialized signatures of previously seen attacks, or on expensive and difficult to produce labeled traffic datasets for profiling and training. In this paper, network attack are detected in unsupervised way without following the traditional way of signatures or labeled traffic.