Casting a SPELL: Sentence Pairing Exploration for LLM Limitation-Breaking

Large language models (LLMs) have revolutionized software development through AI-assisted coding tools, enabling developers with limited programming expertise to create sophisticated applications. This democratization of software development has significantly lowered the barriers to entry for complex programming tasks. However, the same accessibility extends to malicious actors who may exploit these powerful tools to generate harmful software, including malware, ransomware, and other security threats. Existing jailbreaking research primarily focuses on general attack scenarios against LLMs, with limited exploration of malicious code generation as a jailbreak target and insufficient technical expertise to evaluate whether generated outputs align with specified malicious objectives. To address this gap, we propose SPELL, a comprehensive testing framework for LLM developers and the Secure Team, specifically designed to evaluate the weakness of security alignment in malicious code generation. Our framework employs a time-division selection strategy that systematically constructs jailbreaking prompts by intelligently combining sentences from a prior knowledge dataset, balancing exploration of novel attack patterns with exploitation of successful techniques. Extensive evaluation across three advanced code models (GPT-4.1, Claude-3.5, and Qwen2.5-Coder) demonstrates SPELL’s effectiveness, achieving attack success rates of 83.75%, 19.38%, and 68.12% respectively across eight malicious code categories. The generated prompts successfully produce malicious code in real-world AI development tools such as Cursor, with outputs confirmed as malicious by state-of-the-art detection systems at rates exceeding 73%, including four instances flagged as extremely dangerous by all detection tools. These findings reveal significant security gaps in current LLM implementations and provide valuable insights for improving AI safety alignment in code generation applications.