Hybrid detection of application layer attacks using Markov models for normality and attacks

  • Authors:
  • Rolando Salazar-Hernández;Jesús E. Díaz-Verdejo

  • Affiliations:
  • CTIC, Dpt. of Signal Theory, Telematics and Communications, University of Granada, Spain;CTIC, Dpt. of Signal Theory, Telematics and Communications, University of Granada, Spain

  • Venue:
  • ICICS'10 Proceedings of the 12th international conference on Information and communications security
  • Year:
  • 2010

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Abstract

Previous works has shown that Markov modelling can be used to model the payloads of the observed packets from a selected protocol with applications to anomaly-based intrusion detection. The detection is made based on a normality score derived from the model and a tunable threshold, which allows the choice of the operating point in terms of detection and false positive rates. In this work a hybrid system is proposed and evaluated based on this approach. The detection is made by explicit modelling of both the attack and the normal payloads and the joint use of a recognizer and a threshold based detector. First, the recognizer evaluates the probabilities of a payload being normal or attack and a probability of missclassification. The dubious results are passed through the detector, which evaluates the normality score. The system allows the choice of the operating point and improves the performance of the basic system.