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Towards LLM Unlearning Resilient to Relearning Attacks: A Sharpness-Aware Minimization Perspective and Beyond

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arxiv 2502.05374 v4 pith:W3FSSJ6C submitted 2025-02-07 cs.LG cs.CL

classification cs.LGcs.CL
keywords unlearningattacksrelearningoptimizationrobustadversarialdatadefend
verification ladder T0 review T1 audit T2 compute T3 formal
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The LLM unlearning technique has recently been introduced to comply with data regulations and address the safety and ethical concerns of LLMs by removing the undesired data-model influence. However, state-of-the-art unlearning methods face a critical vulnerability: they are susceptible to ``relearning'' the removed information from a small number of forget data points, known as relearning attacks. In this paper, we systematically investigate how to make unlearned models robust against such attacks. For the first time, we establish a connection between robust unlearning and sharpness-aware minimization (SAM) through a unified robust optimization framework, in an analogy to adversarial training designed to defend against adversarial attacks. Our analysis for SAM reveals that smoothness optimization plays a pivotal role in mitigating relearning attacks. Thus, we further explore diverse smoothing strategies to enhance unlearning robustness. Extensive experiments on benchmark datasets, including WMDP and MUSE, demonstrate that SAM and other smoothness optimization approaches consistently improve the resistance of LLM unlearning to relearning attacks. Notably, smoothness-enhanced unlearning also helps defend against (input-level) jailbreaking attacks, broadening our proposal's impact in robustifying LLM unlearning. Codes are available at https://github.com/OPTML-Group/Unlearn-Smooth.

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Cited by 15 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. Crossing the Margin Cliff: Toward Relearn-Robust LLM Unlearning via Margin Calibration

    cs.AI 2026-07 conditional novelty 7.0 of 10

    Margin Calibration, a non-saturating margin-anchored LoRA polish, crosses the margin cliff and cuts post-attack relearn recovery on all 97 populated cells in the paper's stress matrix.

  2. TRACER: Token ReAssignment for Concept ERasure in Generative Recommendation

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    TRACER uses token reassignment for concept-related items plus a coherence regularizer to unlearn specific concepts in generative recommendation while preserving utility better than baselines.

  3. Measuring the Depth of LLM Unlearning via Activation Patching

    cs.CL 2026-05 unverdicted novelty 7.0 of 10

    Introduces Unlearning Depth Score (UDS) via activation patching to quantify LLM unlearning depth and claims it outperforms 20 other metrics in faithfulness and robustness on 150 models.

  4. One Step to the Side: Why Defenses Against Malicious Finetuning Fail Under Adaptive Adversaries

    cs.CR 2026-05 unverdicted novelty 7.0 of 10

    A unified adaptive attack exploits the common weakness across 15 defenses against malicious fine-tuning, showing they only obscure rather than remove harmful model capabilities.

  5. Efficient Unlearning through Maximizing Relearning Convergence Delay

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  9. A Mechanistic Perspective and Circuit-Guided Difficulty Metric for Unlearning

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    BARRIER applies interval arithmetic to SVD-based activation projections to create bounded forget regions that enable aggressive unlearning while providing formal protection for retain distributions via tail bounds on ...

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