Evaluating Feature Selection Methods for Network Intrusion Detection with Kyoto Data

Considering the large quantity of the data flowing through the network routers, there is a very high demand to detect malicious and unhealthy network traffic to provide network users with reliable network operation and security of their information. Predictive models should be built to identify whether a network traffic record is healthy or malicious. To build such models, machine learning methods have started to be used for the task of network intrusion detection. Such predictive models must monitor and analyze a large amount of network data in a reasonable amount of time (usually real time). To do so, they cannot always process the whole data and there is a need for data reduction methods, which reduce the amount of data that needs to be processed. Feature selection is one of the data reduction methods that can be used to decrease the process time. It is important to understand which features are most relevant to determining if a network traffic record is malicious and avoid using the whole feature set to make the processing time more efficient. Also it is important that the simple model built from the reduced feature set be as effective as a model which uses all the features. Considering these facts, feature selection is a very important pre-processing step in the detection of network attacks. The goal is to remove irrelevant and redundant features in order to increase the overall effectiveness of an intrusion detection system without negatively affecting the classification performance. Most of the previous feature selection studies in the area of intrusion detection have been applied on the KDD 99 dataset. As KDD 99 is an outdated dataset, in this paper, we compare different feature selection methods on a relatively new dataset, called Kyoto 2006+. There is no comprehensive comparison of different feature selection approaches for this dataset. In the present work, we study four filter-based feature selection methods which are chosen from two categories for the application of network intrusion detection. Three filter-based feature rankers and one filter-based subset evaluation technique are compared together along with the null case which applies no feature selection. We also apply statistical analysis to determine whether performance differences between these feature selection methods are significant or not. We find that among all the feature selection methods, Signal-to-Noise (S2N) gives the best performance results. It also outperforms no feature selection approach in all the experiments.