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InjecGuard: Benchmarking and Mitigating Over-defense in Prompt Injection Guardrail Models

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arxiv 2410.22770 v3 pith:S2EXWZWR submitted 2024-10-30 cs.CL cs.AIcs.CR

InjecGuard: Benchmarking and Mitigating Over-defense in Prompt Injection Guardrail Models

classification cs.CL cs.AIcs.CR
keywords promptmodelsover-defenseinjecguardinjectionattacksguardnotinject
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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Prompt injection attacks pose a critical threat to large language models (LLMs), enabling goal hijacking and data leakage. Prompt guard models, though effective in defense, suffer from over-defense -- falsely flagging benign inputs as malicious due to trigger word bias. To address this issue, we introduce NotInject, an evaluation dataset that systematically measures over-defense across various prompt guard models. NotInject contains 339 benign samples enriched with trigger words common in prompt injection attacks, enabling fine-grained evaluation. Our results show that state-of-the-art models suffer from over-defense issues, with accuracy dropping close to random guessing levels (60%). To mitigate this, we propose InjecGuard, a novel prompt guard model that incorporates a new training strategy, Mitigating Over-defense for Free (MOF), which significantly reduces the bias on trigger words. InjecGuard demonstrates state-of-the-art performance on diverse benchmarks including NotInject, surpassing the existing best model by 30.8%, offering a robust and open-source solution for detecting prompt injection attacks. The code and datasets are released at https://github.com/leolee99/InjecGuard.

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Forward citations

Cited by 18 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

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    ARGUS cuts context-aware prompt-injection success from 28.8% to 3.8% on AgentLure while keeping 87.5% clean utility, beating prior defenses on the security-utility tradeoff.

  4. Conjunctive Prompt Attacks in Multi-Agent LLM Systems

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    Conjunctive prompt attacks split adversarial elements across agents and routing paths in multi-agent LLM systems, evading isolated defenses and succeeding through topology-aware optimization.

  5. Transferable Direct Prompt Injection via Activation-Guided MCMC Sampling

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  18. Verifying Intent and Harm: A Unified Defense Against LLM-Generated Threats

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