Virus: Harmful Fine-tuning Attack for Large Language Models Bypassing
  Guardrail Moderation
Authors: name: Tiansheng Huang; name: Sihao Hu; name: Fatih Ilhan; name: Selim Furkan Tekin; name: Ling Liu
Published: 2025-01-29 06:24:58

Abstract: Recent research shows that Large Language Models (LLMs) are vulnerable to
harmful fine-tuning attacks -- models lose their safety alignment ability after
fine-tuning on a few harmful samples. For risk mitigation, a guardrail is
typically used to filter out harmful samples before fine-tuning. By designing a
new red-teaming method, we in this paper show that purely relying on the
moderation guardrail for data filtration is not reliable. Our proposed attack
method, dubbed Virus, easily bypasses the guardrail moderation by slightly
modifying the harmful data. Experimental results show that the harmful data
optimized by Virus is not detectable by the guardrail with up to 100\% leakage
ratio, and can simultaneously achieve superior attack performance. Finally, the
key message we want to convey through this paper is that: it is
reckless to consider guardrail moderation as a clutch at straws towards harmful
fine-tuning attack, as it cannot solve the inherent safety issue of the
pre-trained LLMs. Our code is available at https://github.com/git-disl/Virus