评测大模型在钓鱼邮件检测中的准确率与解释一致性,发现不同模型各有优劣。
Evaluating Large Language Models for Phishing Detection, Self-Consistency, Faithfulness, and Explainability
- 用对比学习和偏好优化微调BERT、Llama、Wizard等模型提升钓鱼识别能力。
- Llama模型解释与预测更一致,但判断准确率不高;Wizard准确率高但解释不稳。
- 首次用CC SHAP衡量大模型内部推理一致性,为可信AI提供评估新方法。
钓鱼攻击仍是主流且持续演进的网络安全威胁,攻击者不断升级手法以规避检测系统。尽管人工智能与机器学习取得进展,但实现可解释、一致且可信的钓鱼判断仍具挑战。得益于自然语言处理的发展,大语言模型(LLMs)在特定领域分类任务中展现出潜力。然而,提升模型可靠性不仅需精准预测,还需解释与预测高度一致、内部自洽。核心问题在于:大模型能否既准确分类钓鱼邮件,又能生成与之对齐且自洽的解释?为此,我们微调了基于Transformer的BERT、Llama及Wizard模型,采用二元序列分类、对比学习(CL)与直接偏好优化(DPO),增强其对钓鱼场景的适配性。通过基于SHAP值的一致性度量(CC SHAP),评估模型预测与解释之间的词级对齐程度,检验其内在忠实性与推理合理性。结果表明,尽管Llama模型在解释一致性上表现更优(更高CC SHAP得分),但决策准确性不足;而Wizard虽具备更高预测准确率,但解释一致性较低。
原文摘要 · Abstract (English)
Phishing attacks remain one of the most prevalent and persistent cybersecurity threat with attackers continuously evolving and intensifying tactics to evade the general detection system. Despite significant advances in artificial intelligence and machine learning, faithfully reproducing the interpretable reasoning with classification and explainability that underpin phishing judgments remains challenging. Due to recent advancement in Natural Language Processing, Large Language Models (LLMs) show a promising direction and potential for improving domain specific phishing classification tasks. However, enhancing the reliability and robustness of classification models requires not only accurate predictions from LLMs but also consistent and trustworthy explanations aligning with those predictions. Therefore, a key question remains: can LLMs not only classify phishing emails accurately but also generate explanations that are reliably aligned with their predictions and internally self-consistent? To answer these questions, we have fine-tuned transformer based models, including BERT, Llama models, and Wizard, to improve domain relevance and make them more tailored to phishing specific distinctions, using Binary Sequence Classification, Contrastive Learning (CL) and Direct Preference Optimization (DPO). To that end, we examined their performance in phishing classification and explainability by applying the ConsistenCy measure based on SHAPley values (CC SHAP), which measures prediction explanation token alignment to test the model's internal faithfulness and consistency and uncover the rationale behind its predictions and reasoning. Overall, our findings show that Llama models exhibit stronger prediction explanation token alignment with higher CC SHAP scores despite lacking reliable decision making accuracy, whereas Wizard achieves better prediction accuracy but lower CC SHAP scores.
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