Int. J. Computer Aided Engineering and Technology, Vol. 1, No. 1, 2008 81 Copyright © 2008 Inderscience Enterprises Ltd. Improving ID performance using GA and NN S. Selvakani* Department of Computer Applications, PSN College of Engineering and Technology, Tirunelveli – 627 152, Tamilnadu, India E-mail: sselvakani@hotmail.com *Corresponding author R.S. Rajesh Department of Computer Science and Engineering, Manonmaium Sundaranar University, Tirunelveli – 627 012, Tamilnadu, India E-mail: rs_rajesh@yahoo.co.in Abstract: The internet has been growing at an amazing rate and concurrent with the growth, the vulnerability is also increasing. How to find and detect novel or unknown attacks is one of the most important objectives in current IDS. Most of the current IDS examine all data features to detect intrusions. However, some of the features may be redundant or contribute little to the detection process. This paper mainly addresses the issue of identifying important input features for intrusion detection. This paper proposes an intrusion detection model that is computationally efficient and effective based on mutual information. Then genetic algorithm is applied to generate optimal rules. Those generated rules are used to detect known attacks. RBF is also used to learn and detect unknown attacks. Experimental results on the well-known KDD 99 data set show the achievement of high true positive rates and acceptable low false positive rates and are effective. Keywords: anomaly detection; confusion matrix; genetic algorithm; information gain; knowledge synthesis; radial basis function. Reference to this paper should be made as follows: Selvakani, S. and Rajesh, R.S. (2008) ‘Improving ID performance using GA and NN’, Int. J. Computer Aided Engineering and Technology, Vol. 1, No. 1, pp.81–93. Biographical notes: S. Selvakani is an Assistant Professor of MCA Department at PSNCET, Tirunelveli. She received her MCA degree from Manonmanium Sundaranar University and MPhil degree from Madurai Kamaraj University. She has presented four papers in a national conference and one paper in an international conference. She has published one paper in a national journal and two papers in an international journal. She is currently pursuing her PhD in Network Security. Dr. R.S. Rajesh received his BE and ME degrees in Electronics and Communication Engineering from Madurai Kamaraj University, Madurai, India in the year 1988 and 1989 respectively, and completed his PhD in Computer Science and Engineering from Manonmaniam Sundaranar University in the year 2004.