AI glossary

Lethal trifecta

Lethal trifecta is Simon Willison’s name for three things that, together, let an attacker steal data through an AI tool: access to private data, exposure to content from outsiders, and a way to send information out. Prompt injection can then turn the tool against you. Remove any one of the three and that route closes.

Why it matters at work

An assistant that reads your calendar, accepts invites from anyone and can search the web has all three. Module 8 has you spot the legs in a set-up and choose the one to break.

Sources

• The lethal trifecta for AI agents: private data, untrusted content, and external communication (opens in a new tab) Simon Willison, 16 June 2025.