Brex Releases CrabTrap, an Open-Source Proxy That Uses AI to Intercept and Police AI Agent Traffic in Real Time
Summary
Brex launches CrabTrap, a free open-source AI security proxy that intercepts and polices every outbound request made by AI agents in real time, using a combination of static rules and an LLM-powered judge to block threats like prompt injection and unauthorized API calls before they happen.
Key Points
- CrabTrap is an open-source HTTP/HTTPS proxy developed by Brex that sits between AI agents and external APIs, intercepting and evaluating every outbound request using a two-tier system of deterministic static rules and an LLM-based policy judge before allowing or blocking traffic.
- The proxy provides enterprise-grade security features including HTTPS interception via MITM with custom TLS certificate generation, SSRF protection against private network requests, prompt injection defense, per-IP rate limiting, and a circuit breaker that trips after five consecutive LLM failures.
- CrabTrap ships with a web UI for audit trail review and policy management, supports OpenTelemetry metrics exposed in Prometheus format, logs all decisions to PostgreSQL, and includes an agentic policy builder that analyzes observed traffic to automatically draft security policies.