This study investigates how LLMs can be used for spear phishing, a form of cybercrime that involves manipulating targets into divulging sensitive information. I first explore LLMs’ ability to assist with the reconnaissance and message generation stages of a successful spear phishing attack, where I find that advanced LLMs are capable of improving cybercriminals’ efficiency during these stages. To explore how LLMs can be used to scale spear phishing campaigns, I then create unique spear phishing messages for over 600 British Members of Parliament using OpenAI’s GPT-3.5 and GPT-4 models. My findings reveal that these messages are not only realistic but also cost-effective, with each email costing only a fraction of a cent to generate. Next, I demonstrate how basic prompt engineering can circumvent safeguards installed in LLMs by the reinforcement learning from human feedback fine-tuning process, highlighting the need for more robust governance interventions aimed at preventing misuse. To address these evolving risks, I propose two potential solutions: structured access schemes, such as application programming interfaces, and LLM-based defensive systems.