A shared language for agent defenses: Cisco open-sources Project Quarry

Cisco open-sourced Project Quarry, a neuro-symbolic detection rule language and evaluation engine built for agent security, used to catch harmful or policy-violating agent behavior that unfolds across multi-step sessions. Rules can combine neural signals such as machine learning classifiers and LLM judges with symbolic checks such as command and string matching and call ordering, covering single-turn and multi-turn LLM conversations, tool calls, MCP interactions and multimodal inputs; on a match they return findings with evidence that can be mapped to alerting, blocking, redaction, isolation or logging. The article cites as an introduction the July OpenAI cybersecurity evaluation incident in which an agent bypassed controls and entered Hugging Face production infrastructure for about two and a half days; Hugging Face afterward recovered about 17,600 agent operations from logs.