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The AppSec alphabet soup: A guide to SAST, IAST, DAST, and RASP

Fred Bals

Aug 14, 2018 / 2 min read

Every application security testing tool has advantages and disadvantages. No single solution can ensure you find and fix all vulnerabilities. But application security tools can complement one another and help you secure your applications in each stage of the software development life cycle (SDLC) and beyond. Here’s a quick overview of SAST, IAST, DAST, and RASP and what you should look for when choosing these application security testing tools.

Static application security testing (SAST)

What it is and how it works

SAST is the granddaddy of application security testing, having been in developers’ toolboxes for more than a decade. It helps developers analyze an application’s source code to determine whether security vulnerabilities exist and to ensure conformance with internal coding guidelines. SAST is critical for uncovering and eliminating vulnerabilities in proprietary software early in the SDLC, before the application is deployed.


  • Simplicity to deploy and use
  • Ability to scale
  • Comprehensive support for your programming languages and frameworks
  • Low rate of false positives
  • Easy integration into the SDLC and with other development and CI/CD tools

Interactive application security testing (IAST)

What it is and how it works

IAST is an emerging technology that is rapidly transforming the way application security testing is done. While it’s not a complete replacement for DAST or penetration testing, it is superior to both for finding vulnerabilities earlier in the SDLC—when it is easier, faster, and cheaper to fix them. 


  • Quick, easy deployment
  • Seamless integration into CI/CD workflows
  • Ability to both identify security vulnerabilities and determine whether they can be exploited
  • Ability to identify third-party and open source components, known vulnerabilities, license types, and other potential risk issues
  • Enterprise-level scalability to process hundreds of thousands of HTTPS requests
  • Compatibility with existing automation tests, QA/dev tests, automated web crawlers, unit testing, etc.

Dynamic application security testing (DAST)

What it is and how it works

DAST technologies are designed to detect conditions that indicate a security vulnerability in running applications. Note the difference from SAST, which tests the application as code, not while it’s running.


  • Flexibility to prioritize, schedule, and modify tests easily as business needs change
  • Delivery of thorough analysis for any application
  • Ability to quickly scale up your testing initiatives without being hindered by resource constraints

Runtime application self-protection (RASP)

What it is and how it works

RASP security products integrate with an application to prevent attacks at runtime by analyzing traffic and end user behavior. When RASP products detect an attack, they issue alerts, block application execution for individual requests, and sometimes virtually patch the application to prevent further attack. RASP solutions are not an application security silver bullet. They should complement, rather than replace, your testing strategy.


  • Code-level visibility into applications beyond what a web application firewall (WAF) provides
  • Both passive and active incident response features (e.g., monitoring/alerting and blocking modes)
  • Ability to be configured to log, alert, and block what it identifies as attacks
  • Support for many languages and platforms
  • Autonomous operation, with an on-premises remote server or no remote connectivity whatsoever
  • Coverage for a broad set of vulnerabilities

SAST, IAST, DAST, and RASP—you may not need them all, but any savvy DevSecOps organization will want at least two in their application security toolkit. With tools that complement one another, your teams can inject security into the SDLC at the speed that software development demands today.

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