Framework for Intrusion Detection in IoT Networks: A Lightweight Soft-Voting Ensemble of XGBoost and LightGBM with Explainable AI
The rapid propagation of Internet of Things (IoT) devices has significantly expanded the cyber-attack surface, particularly in essential infrastructure sectors such as energy, water, and healthcare. Machine learning (ML) based intrusion detection systems (IDS) offer a promising defense, but their real-world deployment is often hindered by data imbalance, lack of interpretability, and computational demands. In this paper, we introduce a lightweight ensemble approach, which integrates XGBoost and LightGBM using a soft-voting method. The system is evaluated on the IDSAI dataset after eliminating duplicates, resulting in 693,116 unique samples with a natural class imbalance. The preprocessing phase includes data cleansing and data scaling. The results indicate that the proposed ensemble achieves 99.95% accuracy, 99.95% F1-score, and a perfect AUC of 1.0 on a test set of 207,935 samples. Training completes in under 8 seconds on a standard CPU. The feature importance (gain) highlights delta_time; packet inter-arrival time, as the most significant feature, followed by source/destination ports. SHapley Additive exPlanations (SHAP) analysis provides local explanations, revealing that high inter-arrival times push predictions toward malicious—likely due to slow scanning or burst-and-pause attack patterns. All code and the trained model are publicly available to facilitate reproducibility1.