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TED++: Submanifold-Aware Backdoor Detection via Layerwise Tubular-Neighbourhood Screening

2025/10/16 by Le, Nam, Zhang, Leo Yu, Liao, Kewen +2
#53Z50 #62H30 #68T07 #Artificial Intelligence (cs.AI) #FOS: Computer and information sciences #I.2.6 #I.5.1 #K.6.5 #Machine Learning (cs.LG)

paper · doi:10.48550/arxiv.2510.14299

Abstract

As deep neural networks power increasingly critical applications, stealthy backdoor attacks, where poisoned training inputs trigger malicious model behaviour while appearing benign, pose a severe security risk. Many existing defences are vulnerable when attackers exploit subtle distance-based anomalies or when clean examples are scarce. To meet this challenge, we introduce TED++, a submanifold-aware framework that effectively detects subtle backdoors that evade existing defences. TED++ begins by constructing a tubular neighbourhood around each class's hidden-feature manifold, estimating its local ``thickness'' from a handful of clean activations. It then applies Locally Adaptive Ranking (LAR) to detect any activation that drifts outside the admissible tube. By aggregating these LAR-adjusted ranks across all layers, TED++ captures how faithfully an input remains on the evolving class submanifolds. Based on such characteristic ``tube-constrained'' behaviour, TED++ flags inputs whose LAR-based ranking sequences deviate significantly. Extensive experiments are conducted on benchmark datasets and tasks, demonstrating that TED++ achieves state-of-the-art detection performance under both adaptive-attack and limited-data scenarios. Remarkably, even with only five held-out examples per class, TED++ still delivers near-perfect detection, achieving gains of up to 14% in AUROC over the next-best method. The code is publicly available at https://github.com/namle-w/TEDpp.

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