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anti-backdoor learning

Anti-backdoor learning is a defensive machine learning paradigm designed to train secure and uncompromised neural networks directly from poisoned or untrusted datasets. Rather than relying on post-training methods that detect or repair models after they have already been compromised, this approach intervenes during the training process itself to prevent backdoor triggers from taking hold. It typically leverages differences in learning dynamics between clean and malicious data—such as the tendency of models to fit backdoor shortcuts much faster than natural task features—to identify suspected poisoned examples and suppress or unlearn the associations between malicious trigger patterns and target labels. As a result, the model retains high accuracy on standard inputs while remaining robust against trigger-based manipulation at test time.

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Reconstructive Neuron Pruning for Backdoor Defense

Reconstructive Neuron Pruning for Backdoor Defense

Yige Li, Xixiang Lyu, Xingjun Ma, Nodens Koren, Lingjuan Lyu, Bo Li, Yu-Gang Jiang

OrganizationsFudan UniversityShanghai Artificial Intelligence LaboratorySony CorporationUniversity of CopenhagenUniversity of Illinois Urbana-ChampaignXidian University

Why you should read this

Proposes an asymmetric unlearning and filter-recovery framework that exposes and prunes backdoor neurons using only a small set of clean data, effectively purifying backdoored models across diverse attacks without sacrificing clean classification accuracy.

Deep neural networks (DNNs) have been found to be vulnerable to backdoor attacks, raising security concerns about their deployment in mission-critical applications. While existing defense methods have demonstrated promising results, it is still not clear how to effectively remove backdoor-associated neurons in backdoored DNNs. In this paper, we propose a novel defense called Reconstructive Neuron Pruning (RNP) to expose and prune backdoor neurons via an unlearning and then recovering process. Specifically, RNP first unlearns the neurons by maximizing the model’s error on a small subset of clean samples and then recovers the neurons by minimizing the model’s error on the same data. In RNP, unlearning is operated at the neuron level while recovering is operated at the filter level, forming an asymmetric reconstructive learning procedure. We show that such an asymmetric process on only a few clean samples can effectively expose and prune the backdoor neurons implanted by a wide range of attacks, achieving a new state-of-the-art defense performance. Moreover, the unlearned model at the intermediate step of our RNP can be directly used to improve other backdoor defense tasks including backdoor removal, trigger recovery, backdoor label detection, and backdoor sample detection. Code is available at https://github.com/bboylyg/RNP.

Added

2026-09-26