IAST (Interactive Application Security Testing)
IAST (Interactive Application Security Testing) is a grey-box method that instruments a running application from the inside to observe code execution, data flow, and configuration in real time, confirming vulnerabilities with low false positives as the app is exercised by tests or traffic.
IAST combines aspects of static and dynamic testing. It runs agents or instrumentation inside the application during execution, giving it visibility into both the source-level context (which line handled the request) and the runtime behavior (what data actually flowed). This inside-out vantage point is why it is often called grey-box testing.
While the application runs, whether driven by functional tests, QA activity, or normal traffic, IAST watches how untrusted input moves through the code and whether it reaches a dangerous operation. Because it confirms that a tainted path was truly exercised at runtime, it can validate findings with high confidence and fewer false positives than pure static analysis.
For developers, IAST fits into existing test suites and CI, adding security insight without a separate scanning phase. The trade-off is operational: it requires instrumenting the runtime and only covers code paths that the driving tests or traffic actually reach.