通过对话轨迹几何特征提前识别潜在攻击,比传统内容检测更早有效。
PsychoPass: Geometric Profiling of Multi-Turn Adversarial LLM Conversations
- 将对话建模为嵌入空间中的路径,提取几何特征预测攻击
- 早期片段即能稳定识别攻击,准确率显著高于基线方法
- 特征对编码器不敏感,适合实时监控与部署
大型语言模型的多轮越狱攻击暴露出当前防护机制的缺陷:现有防护针对单轮内容,而攻击是跨轮次展开的动态过程。本文提出从内容检测转向动态分析,将对话视为嵌入空间中的轨迹,探究恶意意图是否在早期就体现于其几何结构中。我们提出PsychoPass框架,从对话轨迹中提取嵌入空间的几何特征,以在有害内容生成前预测潜在攻击。这些特征在简单分类器中表现接近完美,主要归因于对话轮数这一因素。去除该混淆变量后,仍存在微弱但稳定的几何信号,且分类性能不受编码器选择影响。关键的是,该信号在对话初期即显现:仅用短前缀片段即可使攻击判别保持显著高于随机水平,优于现有基线防护。理论分析进一步通过长度与形状分解、基于前缀长度的检测边界及编码器不变性解释了这些现象。结果表明,对抗性对话具有早期、表示鲁棒的几何指纹,适用于在线监测。
原文摘要 · Abstract (English)
Multi-turn jailbreak attacks on large language models (LLMs) reveal a mismatch in current guardrails: they operate on individual turns, while attacks unfold as trajectories across conversations. We propose a shift from content to dynamics, modeling conversations as paths in representation space and asking whether adversarial intent is encoded early in their geometry. We introduce PsychoPass, a framework that extracts geometric features from conversation trajectories in embedding space to predict a potential attack before harmful content is produced. These features achieve near-perfect performance in naïve classifiers, which is largely explained by the inclusion of number of turns as a feature. After removing this confound, a smaller but consistent geometric signal remains, with classification performance that does not depend meaningfully on encoder choice. Crucially, this signal appears early in the conversation: attack outcomes remain above chance from short prefixes alone, more reliably than baseline guardrails. A supporting theoretical analysis explains these findings via a decomposition of length and shape, a detection bound based on prefix length, and encoder invariance. Together, these results show that adversarial conversations leave an early, representation-robust geometric fingerprint suitable for online monitoring.
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