Distillation Robustifies Unlearning

Fuente: arXiv
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Autori principali: Lee, Bruce W., Foote, Addie, Infanger, Alex, Shor, Leni, Kamath, Harish, Goldman-Wetzler, Jacob, Woodworth, Bryce, Cloud, Alex, Turner, Alexander Matt
Natura: Preprint
Pubblicazione: 2025
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author Lee, Bruce W.
Foote, Addie
Infanger, Alex
Shor, Leni
Kamath, Harish
Goldman-Wetzler, Jacob
Woodworth, Bryce
Cloud, Alex
Turner, Alexander Matt
author_facet Lee, Bruce W.
Foote, Addie
Infanger, Alex
Shor, Leni
Kamath, Harish
Goldman-Wetzler, Jacob
Woodworth, Bryce
Cloud, Alex
Turner, Alexander Matt
contents Current LLM unlearning methods are not robust. A few steps of finetuning can revert their effects. We begin by showing that this is true even for an idealized form of unlearning: training to imitate a model that was never trained on unwanted information. This shows that training a model can drastically modify its input-output behavior while leaving its underlying capabilities intact. In light of this dynamic, we show our main result. Training a randomly initialized student on the outputs of an unlearned model transfers behaviors while leaving latent capabilities behind. In short, distillation robustifies unlearning. Based on this result, we propose Unlearn-Noise-Distill-on-Outputs (UNDO), a scalable method that distills an unlearned model into a noised copy of itself. UNDO introduces a tunable tradeoff between compute cost and robustness, establishing a new Pareto frontier on synthetic language and arithmetic tasks. At its strongest setting, UNDO matches the robustness of a model retrained from scratch with perfect data filtering while using only 60-80% of the compute and requiring only 0.01% of the pretraining data to be labeled. We also show that UNDO robustifies unlearning on the more realistic Weapons of Mass Destruction Proxy (WMDP) benchmark. Since distillation is widely used in practice, incorporating an unlearning step beforehand offers a convenient path to robust capability removal.
format Preprint
id arxiv_https___arxiv_org_abs_2506_06278
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Distillation Robustifies Unlearning
Lee, Bruce W.
Foote, Addie
Infanger, Alex
Shor, Leni
Kamath, Harish
Goldman-Wetzler, Jacob
Woodworth, Bryce
Cloud, Alex
Turner, Alexander Matt
Machine Learning
Artificial Intelligence
Current LLM unlearning methods are not robust. A few steps of finetuning can revert their effects. We begin by showing that this is true even for an idealized form of unlearning: training to imitate a model that was never trained on unwanted information. This shows that training a model can drastically modify its input-output behavior while leaving its underlying capabilities intact. In light of this dynamic, we show our main result. Training a randomly initialized student on the outputs of an unlearned model transfers behaviors while leaving latent capabilities behind. In short, distillation robustifies unlearning. Based on this result, we propose Unlearn-Noise-Distill-on-Outputs (UNDO), a scalable method that distills an unlearned model into a noised copy of itself. UNDO introduces a tunable tradeoff between compute cost and robustness, establishing a new Pareto frontier on synthetic language and arithmetic tasks. At its strongest setting, UNDO matches the robustness of a model retrained from scratch with perfect data filtering while using only 60-80% of the compute and requiring only 0.01% of the pretraining data to be labeled. We also show that UNDO robustifies unlearning on the more realistic Weapons of Mass Destruction Proxy (WMDP) benchmark. Since distillation is widely used in practice, incorporating an unlearning step beforehand offers a convenient path to robust capability removal.
title Distillation Robustifies Unlearning
topic Machine Learning
Artificial Intelligence
url https://arxiv.org/abs/2506.06278