8 Best IAST Tools (2026): Runtime Security Testing Compared

What is IAST?

Let us combine SAST and DAST, and now we have IAST.

Now we can look at our washing machine parts while working and get more accurate results!

IAST tools will be installed into the application server and will analyse all application interactions (manual or automated tests) and detect vulnerabilities in real-time.

The key insight behind IAST is that you get the best of both worlds.

Like SAST, IAST can point to exact file and line numbers.

Like DAST, it tests real application behavior.

The combination produces very few false positives because the tool sees exactly which code path handles each request.

False positives are a major problem with legacy security tools, occurring in over 50% of testing results according to industry research. IAST dramatically reduces this noise. Contrast Security reports their IAST approach produces 99% fewer false positives than traditional tools, and in NSA testing, Contrast correctly identified 98% of web application vulnerability test cases with zero false alarms. Forrester estimates DAST scans take 5-7 days while IAST provides real-time results during normal testing.

Advantages

• Combines source code and runtime context
• Very low false positive rate
• Pinpoints exact code location of vulnerabilities
• Works during QA testing
• No separate scan needed — runs during tests

Limitations

• Hard to deploy in cloud-native environments
• Requires test automation for best results
• Language dependent (agent support varies)
• Only sees code paths that tests trigger
• Additional performance overhead

The trade-off is deployment complexity.

IAST agents need to run inside your application.

For traditional VMs, this is easy.

For Kubernetes and serverless, you need to modify container images, which adds complexity.

IAST also depends on test coverage.

If your tests do not exercise a code path, IAST will not find vulnerabilities there.

How IAST Works

IAST uses runtime instrumentation to observe code execution as your application handles requests.

Here is the typical workflow:

Deploy Agent

Install the IAST agent into your application server or container. The agent hooks into the runtime (JVM, CLR, Node.js runtime) to observe code execution. Unlike DAST which attacks from outside, the agent lives inside the application process.

Run Tests

Execute your test suite (manual or automated). The agent observes every code path that tests trigger. More test coverage means more vulnerabilities found. This is why IAST works best with comprehensive automation.

Data Flow Analysis

The agent tracks user input from HTTP request through all code paths to security-sensitive functions (SQL queries, file I/O, command execution). This is called taint tracking — following untrusted data through the application.

Vulnerability Report

When tainted data reaches a sink without proper sanitization, IAST reports the vulnerability with the exact code location — file name, line number, and full stack trace. No guessing needed.

Quick Comparison of IAST Tools

Tool	USP	License
Freemium
Contrast Assess	95%+ true positive rate, free Community Edition	Commercial (Free CE)
Commercial
Datadog IAST	100% OWASP Benchmark score, APM integration	Commercial
HCL AppScan IAST	Patented false positive reduction, auto-correlation	Commercial
Invicti Shark NEW	DAST+IAST combined, Proof-Based Scanning	Commercial
Checkmarx IAST	Unified platform with SAST/SCA/DAST correlation	Commercial
Seeker IAST	Active verification, 14+ languages	Commercial
Acunetix AcuSensor	IAST agent for Acunetix DAST	Commercial
Fortify WebInspect Agent	IAST for OpenText Fortify WebInspect	Commercial
PT Application Inspector	Combined SAST+DAST+IAST+SCA	Commercial
Deprecated
Hdiv Detection	No longer actively maintained	Commercial

IAST vs SAST vs DAST

Understanding when to use each approach helps you build an effective application security program.

They are complementary, not competing.

Aspect	SAST	DAST	IAST
Analyzes	Source code	Running application	Both (code + runtime)
When to run	Any time (no app needed)	Staging/production	During QA testing
False positives	High (no runtime context)	Low (tests real behavior)	Very low (both contexts)
Code coverage	Full codebase	Only reachable paths	Only tested paths
Deployment	CI pipeline	Separate scanner	Agent in app server
Best for	Shift-left, dev feedback	Pre-release validation	High-accuracy QA testing

My recommendation: Start with SAST in your CI pipeline for fast developer feedback. Add DAST for pre-release validation. If you have a mature test automation suite and can deploy agents easily, add IAST for the highest accuracy during QA. Most teams do not need all three.

Deployment Challenges

IAST deployment is straightforward for traditional applications but gets complex in modern architectures.

Traditional VMs

Add the agent JAR or DLL to your application server startup. For Tomcat, add to CATALINA_OPTS. For IIS, install the .NET profiler. Simple one-time setup.

Containers (Docker/Kubernetes)

Modify your Dockerfile to include the agent, or use init containers. Every image rebuild needs the agent. Adds complexity to your CI/CD pipeline and increases image size.

Serverless (Lambda, Cloud Functions)

Most IAST tools do not support serverless. The ephemeral nature of functions makes agent deployment impractical. Consider SAST and DAST instead.

How to Choose an IAST Tool

With only a few active products in the market, the choice is simpler than most categories.

Here are the factors to consider:

Language Support

Contrast Assess and Seeker support Java, .NET, Node.js, and Go. Datadog IAST adds Python. HCL AppScan focuses on Java and .NET with patented instrumentation. Check if your primary language is covered before committing.

Existing AppSec Stack

If you already use Contrast for RASP, adding Assess is seamless. If you use Black Duck for SCA, Seeker integrates well. Datadog IAST makes sense if you already use Datadog for APM. Checkmarx IAST fits enterprises using Checkmarx One. Invicti Shark pairs with Invicti DAST.

Deployment Complexity

IAST requires agent installation. For traditional VMs, this is easy. For Kubernetes, you need to modify your container images. Evaluate the effort for your environment.

Test Automation Maturity

IAST only sees code paths that tests trigger. If your test coverage is low, you will miss vulnerabilities. Make sure your test suite is comprehensive before investing in IAST.

Frequently Asked Questions

What is IAST?

IAST (Interactive Application Security Testing) combines SAST and DAST approaches. An agent runs inside the application during testing and observes both the source code execution and the runtime behavior. This gives high accuracy because the tool sees exactly which code paths are triggered by each request.

How is IAST different from SAST and DAST?

SAST analyzes source code without running it. DAST tests the running application from outside. IAST runs inside the application while it is being tested and correlates both code and runtime data. This hybrid approach reduces false positives significantly.

Does IAST require test automation?

IAST works during any application interaction, including manual testing. However, it provides the most value when paired with automated test suites because it can analyze more code paths. If you only run manual tests, IAST will only see vulnerabilities in the paths you manually trigger.

Why is IAST hard to deploy for cloud-native apps?

IAST requires installing an agent into the application runtime. For traditional server deployments, this is straightforward. For containerized and serverless architectures, you need to modify your container images or deployment scripts, which adds complexity to CI/CD pipelines.

Is there a free IAST tool?

Contrast Assess offers a free Community Edition with limited features. There are no fully open-source IAST tools with active maintenance. The complexity of runtime instrumentation makes IAST hard to build and maintain as an open-source project.

Explore Other Categories

IAST covers one aspect of application security. Browse other categories in our complete tools directory.

AI Security API Security ASPM DAST IaC Security Mobile RASP SAST SCA

Written by

Suphi Cankurt

Suphi Cankurt is an application security enthusiast based in Helsinki, Finland. He reviews and compares 129 AppSec tools across 10 categories on AppSec Santa. Learn more.