Developer Builds AI Agent System That Turns Phishing Prompt Injections Into Evidence

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A developer built an agentic cybersecurity tool called Sentinel, designed to detect and flag phishing domains by monitoring public Certificate Transparency logs in real time. The system uses a layered pipeline of specialized AI agents — including local and cloud-based language models — to triage suspicious domains at near-zero cost, discarding roughly 99% of candidates before any token expense is incurred. A key discovery during development was that phishing pages sometimes embed prompt injection instructions targeting AI crawlers, and Sentinel was redesigned to treat such attempts as forensic evidence rather than simply stripping them. The architecture enforces strict separation of concerns, with a human approval step required before any irreversible takedown action can be triggered. The project also surfaced a real vulnerability where structured protocol data from RDAP could be attacker-influenced, highlighting that deterministic data sources are not inherently trustworthy.

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