REACT: Residual-Adaptive Contextual Tuning for Fast Model Adaptation in Threat Detection

Web and mobile systems show constant distribution shifts due to the evolvement of services, users, and threats, severely degrading the performance of threat detection models trained on prior distributions. Fast model adaptation with minimal new data is essential for maintaining reliable security measures. A key challenge in this context is the lack of ground truth, which undermines the ability of existing solutions to align classes across shifted distributions. Moreover, the limited new data often fails to represent the underlying distribution, providing sparse and potentially noisy information for adaptation. In this paper, we propose REACT, a novel framework that adapts the model using a few unlabeled data and contextual insights. We leverage the inherent data imbalance in threat detection and meta-train weights on diverse unlabeled subsets to generalize common patterns across distributions, eliminating the reliance on labels for alignment. REACT decomposes a neural network into two complementary components: meta weights as a shared foundation of general knowledge, and residual adaptive weights as adjustments for specific shifts. To compensate for the limited availability of new data, REACT trains a hypernetwork to predict adaptive weights based on data and contextual information, enabling knowledge sharing across distributions. The meta weights and the hypernetwork are updated alternately, maximizing both generalization and adaptability. Extensive experiments across multiple datasets and models demonstrate that REACT improves AUROC by 14.85% over models without adaptation, outperforming the state-of-the-art.