Jailbreaking is Best Solved by Definition

The rise of "jailbreak" attacks on language models has led to a flurry of defenses aimed at preventing the output of undesirable responses. In this work, we critically examine the two stages of the defense pipeline: (i) the definition of what constitutes unsafe outputs, and (ii) the enforcement of the definition via methods such as input processing or fine-tuning. We cast severe doubt on the efficacy of existing enforcement mechanisms by showing that they fail to defend even for a simple definition of unsafe outputs–outputs that contain the word "purple". In contrast, post-processing outputs is perfectly robust for such a definition. Drawing on our results, we present our position that the real challenge in defending jailbreaks lies in obtaining a good definition of unsafe responses: without a good definition, no enforcement strategy can succeed, but with a good definition, output processing already serves as a robust baseline albeit with inference-time overheads.