This document discusses implementing a decision tree algorithm for intrusion detection after clustering data through the WEKA machine learning tool. It begins by introducing intrusion detection and the need to reduce false alarms. It then reviews previous work applying machine learning algorithms for classification. The document proposes a new algorithm that performs K-means clustering followed by decision tree classification. It describes constructing datasets from network logs and evaluating algorithms based on classification accuracy and precision of false alarm detection. The results show the combined clustering and classification approach achieves higher accuracy than other algorithms alone.