AI agents, whether built in Copilot Studio or on other platforms, can access data and perform privileged actions based solely on natural language input, which shifts the threat landscape from build-time to runtime. Microsoft Defender researchers describe a need to verify and control agent behaviour as it executes, not just when it is designed, to prevent unintended operations becoming reality inside the agent’s sandbox.
Defender’s webhook-based runtime checks in Copilot Studio analyse each tool invocation in real time, deciding whether to allow or block actions before they execute and logging blocked attempts in the Activity History.
The article outlines three realistic scenarios—malicious instruction injection in an event-triggered workflow, prompt injection via a shared document leading to data exfiltration, and capability reconnaissance to probe internal tools—where real-time protection can stop unsafe actions without disrupting legitimate workflows.
This approach, according to Microsoft Defender Security Research, provides a scalable security layer that evolves with evolving attack techniques and supports confident deployment of AI-powered agents across enterprise use cases.