IAST vs SAST

Definitions of SAST and IAST testing methodologies

Static Application Security Testing (SAST) is a static application analysis technique used to examine the source code or bytecode of an application without executing it, to identify security vulnerabilities in the code. 

Interactive Application Security Testing (IAST) is a proactive application analysis technique that continuously monitors applications during runtime and leverages advanced analytical capabilities to instantly identify and report security weaknesses found in custom code and third party libraries. 

This guide compares the IAST and SAST methodologies, their advantages and limitations, and ideal use cases. By understanding these testing techniques, organizations can prioritize IAST for its superior capabilities, often using SAST as an initial step before adopting IAST for more robust application protection.

Key differences between IAST and SAST tools

The fundamental difference between IAST and SAST testing techniques lies in their approach to testing, leading to significant advantages for IAST.  SAST is a static analysis technique that examines the source code or bytecode of an application without executing it. This provides some initial insights into vulnerabilities but fundamentally limits its ability to find vulnerabilities that only appear during application runtime. In addition, SAST tools will also return reports on vulnerabilities which are actually not exploitable in runtime. These false positives increase the workload of the teams that need to evaluate and fix vulnerabilities substantially. 

In contrast, IAST is a runtime testing approach that combines the best-of-breed from both static and dynamic analysis techniques with intelligent sensors that can directly monitor and observe application  behavior during execution. Such a comprehensive testing approach gives IAST several key advantages:

• Real-World Accuracy: IAST identifies vulnerabilities as they would actually manifest during an attack, reducing false positives and providing a more accurate risk assessment.
• Runtime Coverage: IAST can analyze the entire application stack, including complex libraries and frameworks that often prove difficult for SAST.
• Context-Aware Vulnerability Detection: IAST understands the data flow and interactions within the application, allowing it to detect a broad range of security threats, from common vulnerabilities to complex, logic-based flaws, with the precision and context that SAST often lacks.
• Developer-Friendly Insights: Contrary to SAST tools, IAST tools provide clear, actionable insights that developers can use in real time to improve security without needing specialized knowledge. This method allows developers to make informed security decisions quickly and efficiently.

Pros and cons of SAST testing methods

Most SAST tools analyze the source code of an application to identify potential security vulnerabilities. This analysis is performed before the application is executed, offering a valuable initial layer of security testing. SAST tools typically scan for common coding errors, insecure practices, and known vulnerabilities in the code.

• Pros: 

• Early Detection: Finds vulnerabilities early in the development cycle.
• Codebase Coverage: SAST tools provide a broad overview of potential issues within the codebase.

• Cons:

• False Positives: They can generate false positives (identified problems that aren't really issues), leading to wasted developer effort.
• Runtime Limitations: SAST struggles with complex modern libraries and frameworks, and it misses vulnerabilities that only appear during application execution.
• Depth Constraints: The claim that the entire codebase is being fully analyzed is limited by scan depth and scan times.
• Slow scan times: Scans often take hours to complete which breaks code flow and pipeline automation for modern development teams.

Pros and cons of IAST testing methods 

IAST tools operate during the execution of an application. They are deployed within the application to continuously monitor its behavior, data flows, and interactions with external systems. This dynamic approach provides real-time feedback on security vulnerabilities, including issues that SAST often misses due to its static nature.

• Pros: 
  • Comprehensive Protection: IAST goes beyond the initial analysis provided by SAST, finding and addressing a broader range of vulnerabilities, particularly those that emerge at runtime.
  • Superior Accuracy: Offers more accurate results with fewer false positives, saving development time and resources.
  • Superior Speed: Analysis is completed in real-time and at pipeline native speeds, meaning developers no longer need to wait around for scans to complete.  
  • Context-Aware Reporting: Provides detailed, actionable insights into application behavior, helping developers pinpoint the root cause of vulnerabilities quickly.
• Cons: 
  • Potential Performance Overhead: Might introduce some performance overhead as it runs alongside the application, though this impact is often minimal with modern IAST solutions. Also, most of the time an eventual overhead is not an issue as IAST is usually used in pre-production environments only.
  • Setup and Integration: May require more initial setup and integration into testing environments compared to simpler SAST tools.

Comparing IAST vs. SAST

When to use IAST vs. SAST

The choice between IAST and SAST often depends on the specific needs of the organization and the stage of the software development lifecycle. However, IAST's real-time analysis and comprehensive coverage make it a compelling solution for a wider range of scenarios. Here's a breakdown of when each approach may be considered:

SAST:

• Initial Vulnerability Scans: SAST serves as a valuable first step for identifying the potential volume of basic coding errors, insecure practices, and known vulnerabilities within the source code.
• Code Review Assistance: SAST tools can augment a manual code review process, providing an additional layer of scrutiny before code is merged.
• Compliance Requirements: SAST tools may still form the baseline of an organization's application security requirements or be required by certain compliance and regulatory frameworks.

IAST:

• Pre-Production Testing: IAST is essential for pre-production testing. Its dynamic analysis uncovers a wide range of technical vulnerabilities, including runtime vulnerabilities that SAST often misses.
• Augmented Automated Testing: IAST can leverage existing automated testing pipelines to turn any runtime tests such as integration tests and end-to-end tests into security tests to gain further security insights from this existing test automation.
• Security Monitoring: IAST tools that also provide a RASP module (Runtime Application Self-Protection) empower robust security monitoring in production environments, allowing real-time detection and response to security incidents.
• Comprehensive Security Strategy: For organizations seeking the most thorough protection, IAST and RASP can be used throughout the software development lifecycle, identifying potential security issues from the earliest stages to production.

Benefits of using IAST and SAST together:

Layered Security Approach

Organizations often achieve the highest level of security by utilizing IAST and SAST together. SAST provides an initial code-level scan, covers pure front-end code as well as embedded IoT-type code bases. In comparison, IAST offers ongoing, in-depth analysis and real-time protection for a multi-layered, comprehensive approach for many web applications, APIs, or message queue-driven applications.

Best practices for implementing IAST and SAST

Integrating IAST and SAST into a development workflow is crucial for a robust security posture. Prioritizing IAST and complementing it with SAST where needed leads to the most comprehensive protection. Here are some best practices to consider:

• Introduce early: Introduce IAST and SAST tools as early as possible in the development lifecycle.
• Prioritize IAST Integration: Integrate IAST fully into continuous integration/continuous delivery (CI/CD) pipelines for real-time feedback and to make runtime vulnerability testing an automatic part of the process.
• Utilize SAST Strategically: Use SAST during code reviews and for covering code bases that cannot be instrumented using IAST.

Establish Clear Security Requirements:

• Define clear security requirements and goals for your applications, ensuring IAST is configured to address your highest priority concerns.
• Align IAST and SAST with these requirements, using SAST as a supplementary tool to IAST's core coverage.

• Leverage IAST findings in order to train developers on secure coding practices based on the vulnerabilities that they have introduced, right at the time when that training is needed.
• Emphasize IAST insights to help developers understand how to use IAST's detailed runtime insights (e.g. HTTP request, code walkthrough, stacktraces) to write more secure code from the start.
• Integrate IAST with secure code learning platforms for on-the-spot, just-in-time training.

False Positive Management:

• Implement a process to manage false positives generated by SAST tools.
• Use static analysis configuration options and exception rules to minimize false positives.

Maximize IAST plus RASP for Runtime Monitoring:

• Prioritize Production Use: If available, use Production-optimized IAST and RASP extensively to monitor and actively protect  applications in production environments.
• Robust Alerts: Set up comprehensive alerts and notifications for security incidents detected by IAST, prioritizing rapid response. Use RASP blocking rules for preventing exploits of known and unknown vulnerabilities.

• Maintain a strict update schedule for IAST and SAST tools to stay current with the latest security vulnerabilities.
• Focus on IAST: Regularly review and refine IAST security configurations to adapt to changing threats and ensure maximum effectiveness.

Combine with Other Security Measures:

• Combine IAST and SAST with other security measures like penetration testing and threat modeling.
• IAST as the Cornerstone: Implement a layered security approach with IAST serving as the central pillar of protection. For example, use IAST in order to enhance the quality of your pen tests.

Continuous Improvement:

• Continuously monitor the effectiveness of IAST and SAST.
• Prioritize IAST Feedback: Regularly review and improve security processes, using the actionable insights from IAST as the primary guidance.

What is the best fit for IAST vs. SAST?

IAST and SAST both offer valuable security insights, but IAST dynamic analysis and real-time capabilities make it the more powerful tool for safeguarding applications. IAST’s ability to identify runtime vulnerabilities and provide in-depth monitoring in production environments give Appsec teams unparalleled application protection. While SAST can be useful for initial code scans during early development, organizations seeking the most robust security posture should prioritize IAST. By strategically combining IAST and SAST, organizations can build a multi-layered application security strategy that effectively mitigates risk and reduces the likelihood of vulnerabilities being exploited.

Organizations should consider IAST application testing methods for these other added benefits:

• Shift Left Approach: Integrate security early in the development lifecycle. IAST tools help you "shift left," detecting issues in the development phase before they become costly and risky in production.

• Automated Compliance Reporting: Stay compliant with industry standards and regulations with automated reporting features. Reduce manual oversight and ensure that your applications meet necessary security requirements consistently.

• Continuous Learning: A good IAST tool should adapt to new threats and changes in your applications, learning as it goes. This continuous learning ensures that your security measures evolve, keeping your applications safe against the dynamic threat landscape.