Analytic Synaptic Dynamic Scaling Balancer for Multimodal Deepfake Continual Detection

摘要

Multimodal deepfakes pose growing security threats across diverse domains, driven by rapid advancements in generative models. This demands effective Multimodal Deepfake Continual Detection (MDCD) methods capable of adapting to evolving and heterogeneous deepfake techniques. However, MDCD remains underexplored, facing two major challenges: (1) modality-specific feature disparities limit the effectiveness of simple feature fusion, exacerbating the forgetting of previous forgery-relevant knowledge; and (2) newly introduced deepfake videos initially exhibit limited scale that gradually expand, causing class imbalance dominated by forged samples, undermines authentic content understanding in comming tasks. To address these issues, we propose the Analytic Synaptic Dynamic Scaling Balancer (ADanser) that adapts to modality-specific biases and class imbalance while employing a closed-form update to preserve prior multimodal deepfake knowledge in an evolving data stream. Inspired by synaptic scaling in neuroscience, ADanser introduces a modality synaptic scaling mechanism that applies modality-aware attention to extract discriminative and complementary forgery patterns, improving cross-modal knowledge retention. Additionally, a class-wise contribution balancer dynamically reweights learning signals to reduce class bias and enhance authentic video representation. Extensive experiments on benchmark multimodal deepfake datasets demonstrate that ADanser significantly outperforms state-of-the-art continual learning methods, effectively coordinating adaptation and retention in imbalanced, cross-modal scenarios.