An intrusion detection system based on combining probability predictions of a tree of classifiers

Intrusion detection system (IDS) represents an unavoidable tool to secure our network. It is considered as a second defense line against the different form of attacks. The principal limits of the current IDSs are their inability to combine the detection of the new form of attacks with high detection rate and low false alarm rate. In this paper, we propose an intrusion detection system based on the combination of the probability predictions of a tree of classifiers. Specifically, our model is composed of 2 layers. The first one is a tree of classifiers. The second layer is a classifier that combines the probability predictions of the tree. The built tree contains 4 levels where each node of this tree represents a classifier. The first node classifies the connections in 2 clusters: Denial of Service attacks and Cluster 2. Then, the second node classifies the connections of the Cluster 2 in Probing attacks and Cluster 3. The third node classifies the connections of the Cluster 3 in Remote-to-Local attacks and Cluster 4. Finally, the last node classifies the connections of the Cluster 4 in User-to-Root attacks and Normal connections. The second layer contains the last classifier that combines the probability predictions of the first layer and take the final decision. The experiments on KDD'99 and NSL-KDD show that our model gives a low false alarm rate and the highest detection rate. Furthermore, our model is more precise than the recent intrusion detection system models with accuracy equal to 96.27% for KDD'99 and 89.75% for NSL-KDD.