Evaluating ML-based Intrusion Detection Systems: The Illusion of Model Efficacy
Intrusion Detection has been revolutionized due to the integration of Machine Learning. Improved detection rates, reduced false alarms, and optimized algorithms contribute to the perception of improved systems with optimal accuracy and near-perfect performance, the illusion of model efficacy. However, the value of this effectiveness diminishes when confronted with unseen attacks. In this paper, we go beyond solely algorithmic enhancements and metric adjustments in ML-based Network Intrusion Detection Systems. We design an experiment to test the generalization capabilities of certain classifiers on unseen attacks. Our approach examines the dimensionality parameter's impact through two experimental methodologies, which are applied in two distinct settings. The experimental findings reveal how effectively the models could identify even a fraction of unseen attacks and underscore structural weaknesses in ML-based IDS research and evaluation techniques. Finally, seven evaluation criteria are outlined to address these challenges.