Effective intrusion type identification with edit distance for HMM-based anomaly detection system

As computer security becomes important, various system security mechanisms have been developed. Especially anomaly detection using hidden Markov model has been actively exploited. However, it can only detect abnormal behaviors under predefined threshold, and it cannot identify the type of intrusions. This paper aims to identify the type of intrusions by analyzing the state sequences using Viterbi algorithm and calculating the distance between the standard state sequence of each intrusion type and the current state sequence. Because the state sequences are not always extracted consistently due to environmental factors, edit distance is utilized to measure the distance effectively. Experimental results with buffer overflow attacks show that it identifies the type of intrusions well with inconsistent state sequences.