An MCP Gateway to block the lethal trifecta
Hi there, me and some friends were inspired by Simon Willison's recent post on the "lethal trifecta" (https://simonwillison.net/2025/Jun/16/the-lethal-trifecta/ ) and started building a gateway to defend against it. The idea: instead of connecting an LLM directly to multiple MCP servers, you point them all through a Gateway. The Gateway: - Connects to each MCP server and inspects their tools + requirements - Classifies tools along the "trifecta" axes (private data access, untrusted content, external comms) - When all three conditions are about to align in a…
In plain words
An MCP Gateway is a security layer that sits between language models and multiple MCP servers. It inspects the tools available from each server and classifies them along three risk dimensions: private data access, untrusted content processing, and external communications. When a session threatens to combine all three conditions simultaneously, the gateway blocks the action and alerts the user through a dashboard, preventing the "lethal trifecta" scenario where an LLM could access sensitive data, process external input, and send information externally in a single sequence.
written from the facts on this page · September 2026
From the sources
In the maker’s words, at launch
Hi there, me and some friends were inspired by Simon Willison's recent post on the "lethal trifecta" (https://simonwillison.net/2025/Jun/16/the-lethal-trifecta/ ) and started building a gateway to defend against it. The idea: instead of connecting an LLM directly to multiple MCP servers, you point them all through a Gateway. The Gateway: - Connects to each MCP server and inspects their tools + requirements - Classifies tools along the "trifecta" axes (private data access, untrusted content, external comms) - When all three conditions are about to align in a single session, the Gateway blocks the last step and tells the LLM to show a warning instead. That way, before anything dangerous can happen, the user is nudged to review the situation in a web dashboard. We'd love for the HN community to try it out: https://github.com/Edison-Watch/open-edison Any feedback very welcome - we'll be around in the thread to answer questions.
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