Application Security Testing: How to Find Vulnerabilities Before Attackers Do

What is AST?

AST checks code and applications for vulnerabilities in your system that attackers could exploit. The goal is to find security flaws early so they can be fixed before the application is released. 

The application in question could be any piece of software, be that mobile apps, websites, banking apps, or internal company software. 

Each of these different applications processes critical data, including passwords, credit card numbers, personal information, and confidential business secrets. 

When attackers exploit application weaknesses, they can steal or manipulate important information. This can cause problems for both individuals and businesses.

Application security testing helps prevent these problems before bigger issues arise.

AST works by answering questions such as:

Answering these questions early is critical for maintaining security in modern software development. 

The main types of application security testing 

AST is an umbrella term that encompasses several testing methods, each designed to uncover different types of vulnerabilities. While some analyse source code before an application is deployed, others evaluate live applications or monitor them in production. Together, these approaches provide comprehensive visibility into an application’s security posture.   

Static application security testing analyses an application’s source code, bytecode, or binaries without running the software. Often referred to as white-box testing, SAST provides visibility into the application’s internal code, enabling the identification of security issues early in the software development lifecycle.


You can think of SAST as proofreading your code for security flaws before it is executed. It helps identify issues such as: 


Because SAST is typically integrated into development environments and CI/CD pipelines, your development team can address vulnerabilities before they reach production, reducing both remediation costs and security risk. 

Dynamic application security testing evaluates an application while it’s running. Rather than examining the source code, DAST interacts with the application from the outside—much like a real attacker would.


Often described as black-box testing, DAST scans an application by: 

This approach is particularly effective at identifying runtime issues such as authentication weaknesses, misconfigurations, insecure APIs, and vulnerabilities that only appear when an application is live.

Interactive application security testing (IAST) combines elements of both SAST and DAST. Instead of relying solely on source code analysis or external testing, IAST uses monitoring agents within a running application to observe how code behaves in real time.


As the application is exercised through automated tests or manual use, IAST provides detailed insights into vulnerabilities as they are executed. These insights pinpoint exactly where issues occur in the code.


IAST can identify many of the same vulnerabilities as SAST and DAST while reducing false positives and providing more actionable remediation guidance.

Modern applications often rely on open-source libraries and third-party dependencies. SCA focuses on identifying security vulnerabilities in these external components rather than in the application’s source code. 

An SCA solution scans project dependencies to:

Given that many modern applications are built with hundreds or even thousands of third-party components, SCA has become an essential part of AST. 

Penetration testing is a manual security assessment performed by experienced security professionals who simulate real-world attacks against an application. The objective is not only to identify vulnerabilities but also to determine whether they can be exploited and what impact they could have on the organisation.


Penetration testers think like attackers, combining technical expertise with creativity to uncover security weaknesses that automated tools may miss. During an assessment, they may:

Rather than replacing automated testing methods like SAST, DAST, or SCA, it complements them by validating an application’s security from a human attacker’s perspective and uncovering complex vulnerabilities that require manual investigation.

Integrating AST into the software development lifecycle (SDLC) 

So, where does all of this fit into the development process? 


The main thing to remember is that cybersecurity should be an integral part of the entire software development lifecycle. Continuous testing allows development team to identify vulnerabilities earlier, reduce remediation costs, and release software with greater confidence. 


Rather than treating security as a final checkpoint before release, your organisation should integrate application security testing throughout the software development lifecycle. Different testing methods provide value at different stages—from identifying insecure code during development to exploiting vulnerabilities in production-ready applications.

Strengthen your application’s defences with Infinum 

Application security requires both proactive testing and continuous improvement. At Infinum, we help organisations identify vulnerabilities before attackers can exploit them, providing practical guidance to strengthen security throughout the software development lifecycle.

Expert-led pen testing 

Our certified experts specialise in penetration testing, simulating real-world attacks across: 

This testing uncovers vulnerabilities that automated scans alone can miss. Every engagement combines manual and automated testing aligned with Open Worldwide Application Security Project (OWASP) standards, resulting in clear, prioritised remediation guidance your team can act on immediately. 

We’re accredited under the National Cyber Security Centre CHECK scheme (NCSC CHECK), Council of Registered Ethical Security Testers (CREST), and CREST Simulated Targeted Attack & Response (CREST STAR), and hold certifications including ISO 27001, ISO 9001, and SOC 2.

Red teaming 

For organisations that want to test their overall resilience, not just their applications, we also offer red teaming. Our experts design attack scenarios based on the threats your organisation is most likely to face, using the MITRE ATT&CK framework to simulate real-world adversaries and evaluate your people, processes, and technology together. 

The result is a comprehensive report with practical recommendations to close the gaps that matter most.

Comprehensive security 

Beyond testing, our team helps you build secure software from the ground up or strengthen the security of systems already in production by embedding security practices, such as those covered in this guide, directly into your development process.