arXiv:2608.20378cs.AI2026-08中稿 · the 2026 IEEE 2nd …

提出新方法检测伪装有害意图,能提前发现被包装的危险内容。

Truth Lies Deep: Countering Semantic Camouflage via Latent Intent Verification

论文配图:Truth Lies Deep: Countering Semantic Camouflage via Latent Intent Verification
图 1 · 摘自论文原文
  • 通过分析早期层激活,识别隐藏在安全语境中的有害意图痕迹。
  • 在三个模型上验证,90%以上攻击可被早期特征捕获,而传统检测率不足20%。
  • 无需重训模型,轻量级插件式防御,适合实际部署应对新型攻击。

大型语言模型的安全对齐常流于表面,依赖生成末尾才触发的拒绝机制,无法清除预训练中习得的有害概念。本研究揭示,这种架构断层使模型易受语义伪装攻击——即用良性叙事包裹有害意图(如创作性写作),绕过标准输入输出防护。通过对三种小型语言模型(Phi-3、Qwen2.5、Gemma-2b)在对抗压力下的潜在激活轨迹分析,发现存在普遍的“意图临界点”:通常在总层数15%-20%处,模型对有害意图的原始表征被上下文“安全化”掩盖。结果表明,晚期表示与安全查询几乎无法区分(检测率<20%),而早期表示仍保留可检测的“危害特征”。基于此,本文提出轻量级探测防御方案Latent Intent Verification(LIV)。在PKU-SafeRLHF数据集上的实验显示,LIV在所有测试架构中均比传统防护提升20%-50%,有效中和零日语义攻击,且无需模型重训练。

原文摘要 · Abstract (English)

Safety alignment in Large Language Models (LLMs) is often superficial, relying on refusal mechanisms that trigger only at the final stages of generation without erasing the foundational knowledge of harmful concepts acquired during pretraining. This study demonstrates that this architectural disconnect leaves models vulnerable to Semantic Camouflage -- adversarial attacks that wrap harmful intent in benign narrative contexts (e.g., creative writing), effectively bypassing standard input and output guardrails. By analyzing the latent activation trajectories of three distinct Small Language Model (SLM) families (Phi-3, Qwen2.5, and Gemma-2b) under adversarial stress, this research identifies a universal ``Intent Horizon'' -- a critical depth (typically 15--20\% of total layers) where the model's distinct, pre-trained representation of harmful intent collapses as it contextualizes the query into a ``safe'' narrative. Results indicate that while late-layer representations of camouflaged attacks are mathematically indistinguishable from safe queries (Detection Rate $< 20\%$), early-layer representations retain a distinct, detectable ``harm signature.'' Leveraging this insight, this paper proposes Latent Intent Verification (LIV), a lightweight probing defense. Experiments on the PKU-SafeRLHF dataset demonstrate that LIV outperforms standard guardrails by a margin of 20--50\% across all tested architectures, effectively neutralizing zero-day semantic attacks without requiring model retraining.

模型安全对抗攻击意图检测轻量防御

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