Runtime Application Security Testing

What is runtime application security testing?

Runtime application security testing (RAST) is a security approach that analyzes applications while they’re actively running. Unlike static or dynamic testing, RAST operates inside the application to detect vulnerabilities in real-world execution. 

It observes how code behaves at runtime, identifies security issues in context, and provides actionable insights for remediation, often with fewer false positives than traditional application security testing tools.

By embedding sensors directly into the application or runtime environment, RAST provides deep visibility into how data moves through the system, how APIs are invoked, and whether security controls perform as expected. 

For modern teams working in cloud-native and containerized environments, RAST complements other types of application security testing by adding real-time context from within the code itself.

How RAST complements SAST and DAST in application security

Traditional app security testing methods like static application security testing (SAST) and dynamic application security testing (DAST) each serve unique purposes. 

SAST examines code before it runs, helping identify syntax or logic flaws early in development, while DAST scans compiled applications from the outside, simulating attacks against endpoints to uncover exploitable weaknesses.

Runtime application security testing bridges these two methods. It monitors applications as they execute, providing direct evidence of whether a vulnerability discovered by SAST or DAST is truly exploitable in runtime. This hybrid visibility reduces alert fatigue and accelerates remediation by prioritizing verified risks.

Apiiro’s approach extends this model further through code-to-runtime matching, correlating runtime findings directly to code owners and repositories. This enables teams to pinpoint the exact source of a vulnerability and understand its true business impact.

For organizations modernizing their security workflows, integrating RAST into the testing stack transforms fragmented scans into a continuous, risk-driven feedback loop, from code commit to deployment.

Key capabilities and techniques in runtime application security testing

RAST platforms integrate multiple detection and analysis techniques to provide deep runtime visibility:

• Real-time data flow tracking: Monitors how sensitive information like PII or tokens moves through functions and APIs.
• Context-aware vulnerability detection: Correlates runtime behaviors with known attack signatures to confirm exploitability.
• Security control validation: Verifies that authentication, authorization, and encryption mechanisms are active and functioning properly.
• Automated policy enforcement: Applies runtime policies to detect configuration drift or deviations from secure coding practices.
• Integration with existing testing tools: Connects with application security testing software such as SAST, DAST, and SCA to provide a unified risk view.

These capabilities are amplified when runtime visibility is coupled with architectural intelligence. 

Through integrations with technologies like software graph visualization, teams can visualize the relationships between components and understand how vulnerabilities propagate across their environment. This leads to faster triage, stronger prioritization, and fewer production incidents.

Challenges and limitations of RAST in modern environments

While RAST provides unmatched insight into real execution paths, it also presents challenges:

• Performance overhead: Injecting instrumentation into applications can create minor latency or resource consumption.
• Complexity at scale: Managing sensors and agents across thousands of microservices requires strong orchestration.
• Runtime dependency: RAST only analyzes code that executes, potentially missing inactive modules or dead code.
• Environment alignment: Ensuring parity between testing and production environments is essential for accuracy.

These challenges highlight the importance of connecting runtime insights to a broader visibility framework. 

Continuous monitoring through application detection and response strengthens detection across live environments, while following secure development practices reduces the likelihood of compromise earlier in the pipeline. Linking runtime findings back to architecture and developer ownership, as shown in the introduction of code to runtime, helps ensure that every exploit can be traced, validated, and resolved efficiently.

Related Content: How to guard your codebase: practical steps to prevent malicious code

Frequently asked questions

How is runtime application security testing different from interactive application security testing (IAST)?

IAST instruments are applied during testing, while RAST observes applications in live environments. RAST focuses on runtime behavior, providing continuous insight into real-world exploits and the performance of security controls.

In which environments is RAST most effective?

RAST excels in containerized, microservice, or cloud-native environments where code is continuously deployed, and runtime visibility provides valuable validation beyond static scans.

How do you validate findings from runtime tests that are exploitable?

By correlating runtime events to code owners and repositories, teams can confirm whether vulnerabilities are reachable and exploitable within real workloads before prioritizing fixes.

Can runtime application security testing detect zero-day vulnerabilities?

RAST can expose abnormal or suspicious runtime behaviors that may indicate zero-day attacks, but detection depends on behavioral baselines and rule configuration.

What performance or overhead concerns should teams consider when enabling RAST?

Minor CPU or memory overhead can occur due to instrumentation. Optimized deployment and resource configuration minimize these effects in production systems.