NeuronGuard: Robust LLM Safety Alignment via Ablation-Aware Safety Signal Redistribution

Anjun Gao, Yueyang Quan, Yufei Xia, Zhuqing Liu, Minghong Fang


Abstract
Safety alignment in large language models (LLMs) remains brittle against a growing spectrum of attacks. Jailbreak attacks bypass safety mechanisms through crafted prompts, while neuron-level attacks directly prune safety-critical neurons post-deployment. Both exploit a common weakness: safety-relevant information concentrates in a sparse neuron subset. We present NeuronGuard, a fine-tuning-stage defense that simultaneously hardens LLMs against both attack classes by redistributing safety signals across a broader set of neurons. NeuronGuard dynamically identifies safety-critical neurons via periodically refreshed per-layer linear classifiers, forces refusal behavior under deliberate neuron ablation, and applies KL-divergence regularization for distributional consistency. A randomized gradient projection strategy preserves downstream task utility by resolving conflicts between the defense and task objectives. We provide a formal guarantee that NeuronGuard strictly reduces the attack success rate (ASR) upper bound, and experiments across three LLMs, six state-of-the-art attack strategies, and multimodal settings confirm near-zero ASR while maintaining task accuracy, including against white-box adaptive adversaries.
Anthology ID:
2026.findings-emnlp.307
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
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SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
6495–6514
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URL:
https://aclanthology.org/2026.findings-emnlp.307/
DOI:
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Cite (ACL):
Anjun Gao, Yueyang Quan, Yufei Xia, Zhuqing Liu, and Minghong Fang. 2026. NeuronGuard: Robust LLM Safety Alignment via Ablation-Aware Safety Signal Redistribution. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 6495–6514, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
NeuronGuard: Robust LLM Safety Alignment via Ablation-Aware Safety Signal Redistribution (Gao et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.307.pdf