Agent-level code injection is the insertion or delivery of malicious code into software agents running on endpoints, such as EDR clients, update agents, or remote management agents. These agents usually run with elevated privileges so they can collect telemetry, enforce policy, and receive commands from a central server. If an attacker can tamper with that channel or the server behind it, the agent may execute attacker-controlled code as trusted software.
This matters because agents sit inside the trust boundary of many defenses. A successful injection can turn a management platform into a distribution mechanism for malware, persistence, or lateral movement. In real attacks, defenders look for unauthorized policy changes, unexpected package deployments, abnormal agent callbacks, and signs that management credentials or servers were abused. Hardening the control plane, limiting administrative access, and verifying signed updates help reduce the risk.