Modern application security must be built in from the outset and reinforced continually throughout the software development lifecycle. Even organizations with mature application development practices need automated tools to successfully and repeatably secure their software in complex, fast-changing environments.

Security leaders commonly focus on ensuring software security through runtime protection measures, with major cloud service and infrastructure providers even including basic security tools as standard for cloud-based deployments. Keeping track of CVEs to identify and patch vulnerable software products and components is also part of the AppSec routine. But to stay ahead of threats, application security also needs to incorporate vulnerability testing to proactively identify and mitigate security risks.

This post compares the most widely used categories of AppSec tools for testing: SAST and SCA for static analysis, DAST for dynamic application and API security testing, and IAST to bridge the gap between static and dynamic analysis. We explain how the tools work, explore their strengths and tradeoffs, and help you select tools that work for your organization.

Why you need AppSec tools

Multiple converging trends are making software harder to secure—and increasing the risks for users. Code bases keep growing larger and more complex, with more internal and external interactions than ever. Cloud-native and microservice-based development approaches that rely heavily on APIs present new challenges. Software draws on components from more sources, in multiple languages, with varying provenances.

All this adds up to application security complexity that’s beyond the abilities of any dev or DevOps team to manage through manual interactions with a security team alone, and growing and changing at a speed that far outpaces traditional approaches based on penetration testing. As those teams are transformed to build a DevSecOps culture, they need automation and smarter tools to identify security issues as early as possible and speed up remediation.

Attackers know how vulnerable you are, which is why they’re especially focused on web applications and APIs to extract valuable and sensitive data. With Verizon’s 2024 Data Breach Investigations Report showing a massive 180% jump in attacks involving the exploitation of application vulnerabilities in 2023, having the right application security testing tools and processes in place is critical if you want to avoid becoming the next data breach headline.

Types of web application security testing tools

No single category of tool can cover every aspect of web application security, so organizations typically combine multiple AppSec tools to protect applications throughout their lifecycle. Security testing is the crucial foundation of application security, allowing you to find and remediate issues all across the development and operations pipeline. While organizations have traditionally relied on internal and external pen testers for this, modern SaaS security solutions have made it possible to bring a lot of security testing in-house. Let’s go through the major categories of application security testing tools. 

Static application security testing (SAST)

SAST tools automatically analyze the source code, bytecode, or binaries before the application is deployed, attempting to identify vulnerabilities so they can be fixed before they get into production. SAST tools can be used to define code security requirements alongside other code quality checks, either directly in the IDE or as separate steps in the toolchain.

SAST is also called white-box testing or inside-out testing because it has access to the internal application code, allowing SAST tools to pinpoint potential security vulnerabilities in the code. The main advantage of SAST is the ability to test code fragments and components even if they’re not yet part of a runnable application.

Being tied to static source code is a virtue but also a limitation for SAST tools. For one thing, they require access to that code. Sometimes that can’t be provided, especially for third-party modules or products, meaning you can only test first-party code. They are also highly prone to false positives because they cannot know the wider context in which the code will operate, increasing the risk that real vulnerabilities will be ignored in the alert noise.

Different programming languages require separate SAST tools, complicating the workflow and potentially increasing costs. Finally, static code analysis cannot prove that a suspected issue will indeed be exploitable, and it won’t find issues that only appear at runtime, such as misconfigurations, business logic vulnerabilities, or vulnerabilities introduced by dynamic dependencies.

Dynamic application security testing (DAST)

DAST tools check the security of running applications in staging and real-world environments, probing them from the outside by safely mimicking attacker behaviors. Dynamic analysis works from the outside with no visibility into source code, so it’s sometimes called black-box testing. Because it doesn’t require access to source code, DAST is technology-agnostic and can be used to test web applications regardless of the specific language or combination of languages.

DAST tools can uncover misconfigurations, encryption or authentication problems, and exploitable OWASP Top 10 vulnerabilities, including cross-site scripting (XSS) and SQL injection. As such, they provide far more visibility into the overall security posture, covering all running first-party and third-party code, no matter where it originated or how it’s deployed.

With the most modern DAST solutions, it is now possible to perform vulnerability scanning not only in staging and production but also earlier on in the development pipeline, for instance on build candidates. They can also integrate directly into CI/CD pipelines at multiple stages of the DevOps process to trigger scans automatically and retest fixes.

In terms of accuracy, DAST tools tend to have far lower false positive rates than static code analysis, with leading solutions like Invicti even being able to test whether an issue is remotely exploitable. Being technology-agnostic, DAST is far easier and quicker to set up than AppSec tools that require source code access, often delivering the first results within hours of deployment. It’s also the only approach to AppSec testing that can be used in development, staging, and production.

Interactive application security testing (IAST)

IAST tools (aka gray-box testing systems) can be considered to occupy the middle ground between SAST and DAST, as they aim to combine runtime insights with access to software internals. Some standalone solutions require code instrumentation while others act like a plugin to the app runtime, with the latter approach also being taken by integrated IAST. Depending on the product, testing might be triggered by a test suite during the build process or by a DAST scanner.

While for most products the “interactive” in the name can be misleading, implementations such as Invicti’s DAST-based true IAST are indeed interactive because the DAST scanner and server-side IAST sensor work in tandem at all times. For each IAST-enabled security check, DAST initiates a specific test and analyzes the app’s external reactions to it. At the same time, the sensor is plugged into the application runtime and observes the same reactions from the inside, with the combined results being presented to the user in a unified format.

Unlike standalone IAST products, which have become much less popular in recent years, the Invicti approach doesn’t require any code instrumentation and does not limit the whole security testing process to any specific language or technology. The DAST scanner still provides technology-agnostic test coverage, with Invicti’s true IAST delivering additional insights on top of already detailed DAST results for supported languages.

Software composition analysis (SCA)

While it doesn’t have “testing” in the name, software composition analysis (SCA) is another vital part of the AppSec toolbox, allowing organizations to identify open-source code components within the application, highlight known vulnerabilities within them, and often also ensure license compliance. Note that while conventional SCA relies on source code and dependency analysis and thus shares many of the limitations of SAST, some DAST solutions (such as Invicti) can perform dynamic SCA and web technology analysis to detect vulnerable libraries, frameworks, and server versions.

API security testing

Many organizations (and online resources) treat application security and API security as completely separate areas when, in fact, the two are closely interrelated. An API, or application programming interface, is merely a non-GUI way of accessing application functionality, so you should treat APIs as an integral part of your attack surface and use app security testing tools that can cover both GUI and API vulnerabilities.

Read more about building API security testing into the SDLC

How to choose the right tools for your team and organization

As you plan investments in AppSec tooling, there are many factors to consider. Here are just a few of them:

• Effectiveness. How do the tools you’re considering stack up on authoritative industry measurements? Taking DAST as an example, how did the tool perform in tests such as Shay Chen’s web vulnerability scanner benchmark? Can the tool find everything you need to see? Can it crawl and scan JavaScript-heavy SPAs? Can it run authenticated scans? Is it configurable and customizable enough to safely probe deeply into each of your unique applications?
• Accuracy. If your security engineers and developers can’t trust the reports they get from a tool, they will need to manually validate everything it tells them—which is expensive and fundamentally incompatible with rapid development. Features like Invicti’s Proof-Based Scanning can sidestep the problem of false positives by automatically confirming the majority of exploitable vulnerabilities.
• Ease of deployment and time to value. After acquiring an AppSec tool, companies often struggle to operationalize it and start seeing actual value. What will it take to get started and then go live with the tool? Compared to other testing approaches, DAST stands out for its ease of deployment and tech-agnostic testing coverage. Leading DAST solutions can go from a standing start to effective mitigations in a matter of days, if not hours.
• Visibility and flexibility. Will the tool only cover a narrow section of your overall attack surface, as in the case of SAST tools that are necessarily limited to specific languages and constrained by code availability? Can you easily make test results a part of your vulnerability management process, whether integrated into the tool or using a dedicated security platform? Can you use it as a security gauge for the entire organization?
• Workflow integration. No security solution stands alone, but AppSec tools need to integrate especially tightly and efficiently into development workflows. Ask yourself how a tool will fit into your existing processes and toolchains. Will it help you run security testing not only earlier in the SDLC but also at multiple points across it? Will it help improve collaboration and eliminate silos? Is it going to deliver vague information that triggers finger-pointing, or will you get detailed bug reports accompanied by proof?
• Maturity and support. The AppSec market is full of commercial and open-source tools, but a tool never runs or maintains itself. Can you count on vendor support and guidance from onboarding to full-scale production? Is the tool mature enough to safely run all the testing you need and deliver results you can automate without fear of false alarms and delays?

The importance of choosing the right AppSec tools and processes

All AppSec tools are not equal, and neither are all approaches to implementing a cybersecurity program in practice. From picking ineffective tools just to check a compliance box to neglecting proactive testing, having the wrong AppSec tools and processes can add complexity, cost, and frustration to an already challenging development process. Conversely, having the right security tools in place can not only improve your security posture but also help your development, operations, and security teams work more effectively—all while reducing the costs of external security assessments by bringing most of your security testing in-house.

Having the right application security tools is now a practical necessity to proactively manage cybersecurity and business risk. Learn how Invicti has brought proactive prioritization to application security testing with Predictive Risk Scoring.