Anomaly Detection with Adaptive and Aggressive Rejection for Contaminated Training Data
In anomaly detection, training data are often contaminated by anomalous samples, yet conventional methods rely on a predefined contamination rate—rendering them ill-suited to real-world scenarios where the contamination level is both unknown and variable, especially under significant overlap between normal and anomalous distributions. To address this, we propose an Adaptive Aggressive Anomaly Rejection (AAAR) framework that synergistically integrates hard rejection—via dynamically refined z-score thresholds—with soft rejection—based on probabilistic modeling using Gaussian Mixture Models—and employs an adaptive threshold learning mechanism for precise identification and removal of contaminated samples. Crucially, AAAR requires no prior knowledge of contamination rate. Evaluated on 2 image and 30 tabular benchmark datasets, it achieves an average AUROC improvement of 0.041 over state-of-the-art baselines, significantly enhancing model robustness, detection accuracy, and cross-domain generalization capability.