Mitigating label noise in network intrusion detection via graph-based sample selection and purification

Machine learning has achieved notable progress in malicious traffic detection, yet its effectiveness highly depends on data that are sufficiently large and reliably labeled. In practice, many datasets are produced by automated labeling pipelines, which inevitably introduce label noise and, in turn, undermine detection performance. Consequently, maintaining robust and generalizable detection under label noise has become a central challenge in network intrusion detection. Existing approaches often emphasize intrinsic model robustness. However, noise can reshape the distribution of hard examples and bias the optimization objective, which may yield unstable decision boundaries and further degrade performance. In this paper, we propose a data-centric relabeling framework [Formula: see text] , comprising two components: Normal Sample Discovery (NSD) via graph propagation and Malicious Sample Screening (MSS) with dual networks. NSD proceeds in three steps: (1) confident-sample selection; (2) K-NN graph construction; and (3) label propagation. We first select high-confidence samples and assume their labels are correct, build a graph over all samples, and propagate labels from the confident subset to the full graph; samples that remain uncertain after propagation are forwarded to MSS for second-stage annotation. NSD aims to recover the majority of correctly labeled instances; these instances act as reliable anchors that guide MSS in labeling the remaining uncertain samples, thereby reducing label noise and stabilizing training. We evaluate [Formula: see text] on CIC-IDS2017 and DoHBrw-2020. Under 40% label noise, [Formula: see text] attains F1 scores of 0.81 and 0.98, respectively, yielding 17.39% and 11.36% relative improvements over state-of-the-art baselines.