Abstract
Most intrusion detection techniques suffer from either an inability to detect unknown intrusions, or unacceptably high false alarm rates. However, there lacks a general basis to analyze and find solutions to these problems. In this paper, we propose such a theoretical basis for intrusion detection, which makes it possible to systematically express and analyze the detection performance metrics such as the detection rate and false alarm rate in a quantified manner. Most importantly, the insights gained from the basis lead to the proposal for a new intrusion detection technique – USAID. USAID attempts to exploit the advantages of both techniques, and overcome their respective shortcomings. The experimental results show that USAID can achieve uniform level of efficiency to detect both known (99.78%) and new intrusions (98.18%), with a significantly reduced false alarm rate (1.45%). Most significantly, the performance of USAID is superior to all the participants in KDD’99 if the anomalies detected by USAID can be categorized correctly.