Runtime instrumentation is the practice of adding software agents, probes, or hooks to an application so its behavior can be observed while it is running. Instead of only analyzing source code or network traffic, the instrumented program exposes events such as function calls, SQL queries, authentication checks, memory access, and error handling in real time.
In cyber security, runtime instrumentation matters because it gives defenders execution context. Tools such as IAST rely on it to connect a test action to the exact code path that was reached, making vulnerabilities easier to confirm and fix. It is also useful for telemetry, threat detection, and policy enforcement in production. Attackers may try to evade or disable instrumentation, while defenders use it to spot exploit paths, unsafe input handling, and unexpected behavior that static scans can miss.