Application Security Testing: Types, Tech, and 5 Critical Best Practices

What Is Application Security Testing?

Application Security Testing (AST) is the process of reviewing and analyzing an application to identify potential security vulnerabilities. This is not limited to the code of the application but also includes the infrastructure and architecture of the application.

AST makes it possible to anticipate and mitigate potential security risks, preventing malicious attacks and ensuring the robustness of the application. It is a proactive approach, where the aim is to identify vulnerabilities and weaknesses before they can be exploited. This can include anything from unauthorized access to code injection, scripting attacks, session hijacking, misconfigurations, and even business logic errors that could create security risks.

Application security testing is a comprehensive process that encompasses multiple techniques and methodologies. In this article, we’ll cover the most important ones and provide best practices you can use to create an effective AST process in your organization.

This is part of an extensive series of guides about Security Testing.

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The Role of Application Security Testing in Development

Application security testing is becoming an inseparable part of the developmental stages of an application. It is being integrated into the software development life cycle (SDLC) to ensure that applications are secure from the get-go. This approach, in which developers work closely with operations and security teams through the application lifecycle, is known as DevSecOps.

AST is a continuous effort that begins with the design of the application, where potential security threats are identified and security controls are established. During the development phase, security testing is conducted to ensure that the application adheres to the predetermined security controls. The process of moving security efforts “left”, to the beginning of the development process, is known as “shift left”.

At later stages, AST is used to validate the security of the application in testing and staging environments, ensuring that it is ready for deployment. Post-deployment, AST continues to play a role in maintaining the security of the application. It is used to monitor the application, identify new threats, and update security controls as needed.

Application Security Testing Approaches

Application security testing can be conducted in various ways, each with its strengths and weaknesses. A successful AST program combines all these methods to comprehensively test applications.

Black-Box Security Testing

Black-box security testing is a method where the tester does not know the internal workings of the application. This type of testing simulates an external attack and is typically done from an end-user's perspective. The primary goal is to identify vulnerabilities that can be exploited without knowledge of the code or architecture. This method tests the application as a whole, focusing on input and output, to identify security issues such as input validation errors, session management issues, and vulnerabilities in external integrations.

Black-box testing is beneficial because it simulates real-world hacking scenarios, where attackers usually have no internal knowledge of the application. It is a practical approach for finding a wide range of vulnerabilities, particularly those affecting user inputs. However, since it does not delve into the code structure, some vulnerabilities may remain undetected. Additionally, black-box testing can be time-consuming and less systematic compared to white-box testing, as it relies on trial-and-error methods.

White-Box Security Testing

White-box security testing, also known as clear-box or glass-box testing, involves a thorough examination of the internal logic and structure of the code. The tester has full access to all source code and architecture documentation. This approach is used to identify vulnerabilities that are difficult to detect from the outside, such as code path issues, code execution problems, and security misconfigurations. It involves techniques like code analysis, examining data flow, and understanding control flow.

White-box testing allows for a more comprehensive and detailed examination of the application's security posture, as it examines all aspects of the code. It is effective in identifying hidden vulnerabilities and ensuring secure coding practices. However, this method can be resource-intensive and requires skilled testers with a deep understanding of the application’s architecture and coding language. Additionally, while white-box testing is thorough, it may not identify vulnerabilities that only become apparent when the application is in operation, such as runtime issues or interactions with other systems.

Gray-Box Security Testing

Gray-box security testing is a hybrid approach that combines elements of both black-box and white-box testing. It provides the tester with limited knowledge of the internal workings of the application, typically access to some documentation and possibly some code. This approach is used to simulate an attack with partial knowledge, akin to what an insider might have. Gray-box testing focuses on areas such as API endpoints, backend processes, and the interaction between different components of the application.

The advantage of gray-box testing is that it provides a more realistic approach to testing than white-box testing, as it doesn't require complete knowledge of the application's internals. It can identify vulnerabilities that are missed by black-box testing but are not as resource-intensive as white-box testing.

Gray-box testing is particularly useful for identifying issues related to improper use of APIs, broken authentication and session management, and issues resulting from the interaction between various components. However, like black-box testing, it may miss some vulnerabilities that are deeply embedded in the code and can be identified only through a thorough white-box approach.

Tzvika Shneider

CEO, Pynt

Tzvika Shneider is a 20-year software security industry leader with a robust background in product and software management.

Tips from the expert

Enable continuous scanning: Implement continuous security scans for running APIs to catch security vulnerabilities as they appear in real-time environments.
Simulate real-world attack scenarios: Test your APIs using realistic attack simulations to identify vulnerabilities that may not be evident under normal testing conditions.
Incorporate input validation in tests: Conduct tests focusing on input validation to ensure the application correctly handles unexpected, malformed, or malicious input data.
Integrate with alerting systems: Set up integrations with alerting systems to notify relevant teams immediately when a critical vulnerability is detected during testing.
Assess API error responses: Test for excessive information disclosure in error messages, which can reveal sensitive details about the system’s inner workings.

Types of Application Security Testing Solutions

There are several types of AST solutions. Each one operates differently and is designed to identify specific types of vulnerabilities or operate at a different stage of the SDLC.

Static Application Security Testing (SAST)

Static application security testing, a white box testing solution, involves analyzing the source code of an application without executing it. The primary purpose of SAST is to identify vulnerabilities in the code that could be exploited by hackers.

SAST is typically conducted early in the SDLC, even before the code has been compiled. It is capable of scanning large codebases, making it efficient in identifying security vulnerabilities. However, as it does not execute the code, it cannot identify runtime vulnerabilities.

Dynamic Application Security Testing (DAST)

Dynamic application security testing, a black box testing technology, involves testing the application in its running state. This is typically done after the application has been developed and is functioning. DAST aims to identify vulnerabilities that can be exploited during the application's operation.

Unlike SAST, DAST can identify runtime vulnerabilities and security issues arising from the application's interaction with other systems. However, DAST is not useful at early stages of application development, because it can only work with running software modules.

Learn more in our detailed guide to DAST tools

Interactive Application Security Testing (IAST)

Interactive application security testing (IAST) is a combination of both SAST and DAST and is considered a gray-box testing method. It is designed to identify vulnerabilities in both the static and running states of an application. IAST is implemented into the application as an agent and can monitor the application's performance in real-time.

IAST has the advantage of being able to identify vulnerabilities in the runtime that SAST can't, and it provides more context than DAST, making it easier to understand and fix the vulnerabilities. However, it is resource-intensive and can be complex to maintain.

API Security Testing

API security refers to the practices and technologies used to protect application programming interfaces (APIs) from malicious attacks and unauthorized access. As APIs become a critical part of modern software architectures, ensuring their security is essential. API security testing focuses on identifying vulnerabilities in APIs, such as authentication and authorization flaws, injection attacks, and data exposure issues.

The first step in API security is to thoroughly document all APIs, including their endpoints, parameters, and expected behavior. Automated API discovery tools can automate this process and ensure comprehensive discovery of APIs in your environment. API security testing ensures proper authentication, authorization, and input validation. It's crucial for protecting sensitive data and preventing unnecessary data exposure. Additionally, it involves checking APIs against business logic vulnerabilities and aligning with the OWASP Top 10 for API security, which lists the most critical security risks to web applications.

Related content: Read our guide to web security testing

Dedicated API security testing tools are essential for 'shift left' in API security. They integrate with API development toolsets and CI/CD pipelines, aiding developers, testers, and DevSecOps in identifying security issues early in the API creation process. While tools like DAST and IAST test APIs under static and runtime conditions, they often fall short in addressing the unique security needs of APIs, emphasizing the need for more specialized solutions in API security.

Learn more in our detailed guide to API Security

Software Composition Analysis (SCA)

Software composition analysis (SCA) is a type of AST that focuses on identifying vulnerabilities in open-source components of an application. Modern applications often utilize thousands of open-source components, which can introduce vulnerabilities if not properly managed.

SCA tools scan the codebase to identify open-source components and compare them against databases of known vulnerabilities. It can also help identify legal and licensing issues with open-source components (for example, non-permissive licenses). SCA is a crucial component of an AST strategy, given that many devastating attacks in recent years were driven by vulnerabilities in open-source components.

Runtime Application Self-Protection (RASP)

Runtime application self-protection, or RASP, is a security technology specifically designed to detect and prevent real-time application attacks. It operates from within the application itself and is capable of identifying malicious behavior, stopping attacks as they happen, without the need for human intervention.

RASP solutions work by integrating directly into the application's code. This allows them to closely monitor the application's behavior and environment for any signs of security threats. Upon detecting an attack, the RASP solution can immediately take action, such as terminating the user session or stopping the execution of malicious code.

The primary advantage of RASP over other security solutions is its ability to provide real-time protection. Because it operates from within the application, it can respond to threats immediately, minimizing the potential damage caused by attacks.

Mobile Application Security Testing (MAST)

Mobile applications have become a primary target for cybercriminals. Mobile application security testing (MAST) involves the use of tools and techniques to identify vulnerabilities in mobile applications that can be exploited by attackers.

MAST tools scan the mobile application's code, user interface, and network communication for potential security flaws. They check for issues such as insecure data storage, weak encryption, and improper session handling, among others. Once these vulnerabilities are identified, they can then be addressed before the application is released to the public.

Database Security Scanning

Databases often contain sensitive information, making them attractive targets for cybercriminals. Database security scanning aims to identify vulnerabilities in databases that could be exploited by attackers.

Database security scanning tools analyze the database's structure, configurations, and permissions for potential security risks. They look for issues such as weak passwords, misconfigured settings, outdated software versions, and lack of proper sanitization for user inputs, and provide remediation guidance. Regularly scanning databases for vulnerabilities and remediating discovered issues can significantly improve data security.

Related content: Read our guide to DAST vs SAST

5 Best Practices for Application Security Testing

1. Use SBOM to Review Third-Party or Open Source Components

Using third-party or open-source components is standard practice in software development. These components can save significant development time, provide proven functionality, and even offer access to a community of developers for support. However, they also raise the risk of hidden vulnerabilities or malicious code that can compromise your application's security.

A Software Bill of Materials (SBOM) is a comprehensive list of components, libraries, and modules used to build software. It provides visibility into the makeup of your software, allowing you to identify and review third-party or open-source components. With a well-structured SBOM, you can keep track of potential vulnerabilities and ensure that all components are up-to-date, reducing the risk of security breaches. This also allows you to demonstrate to others, such as customers, partners, or compliance auditors, that your software is safe.

SCA tools can help you create and automatically update an SBOM for your own software projects. When using software from other vendors, it is important to require an SBOM and carefully review it to make sure all components are safe.

2. Use Robust Test Cases That Include Malicious Attacks

Application security testing should not only focus on lists of known vulnerabilities, such as CVEs. It is important to include complex test cases with scenarios that mimic real-world malicious attacks.

When designing these test cases, it's crucial to think like a hacker. What parts of your application might be most attractive to an attacker? Where are your most significant vulnerabilities? By identifying these areas and creating test cases that target them, you can more effectively secure your application. Black-box testing tools like DAST are especially effective at testing attack scenarios.

Your test cases should also take into account the types of threats your application might face. For web applications, mobile applications, or APIs, a good starting point is to make sure you cover the relevant OWASP Top 10 list, which includes the most severe security vulnerabilities. It is important to conduct threat modeling and identify additional threats that apply to your specific use case.

3. Integrate AST into Your CI/CD Pipeline

Continuous Integration/Continuous Deployment (CI/CD) is a modern software development practice that involves regularly committing all code to a shared mainline and then deploying that code frequently to a production environment. By integrating AST into your CI/CD pipeline, you can ensure that security testing is conducted continuously and automatically, reducing the risk of vulnerabilities slipping through the cracks.

In a CI/CD pipeline, every code commit triggers a build and a series of tests. These should include automated security tests. Security tests should “break the build” and notify developers immediately. This ensures that any vulnerabilities are detected and fixed as early as possible, reducing the potential damage they might cause.

The integration of AST into the CI/CD pipeline also allows for a more efficient and streamlined testing process. Instead of having to schedule and conduct security tests separately, they are automatically performed as part of the continuous integration process, ensuring that no code changes go untested.

4. Perform Simulations to Challenge Your Risk Response Processes

It is important to perform realistic simulations that challenge your application security processes. These simulations, often referred to as "red teaming" or "penetration testing," involve simulating real-world attacks on your applications to test your defenses' effectiveness. They can be conducted by in-house security experts or hired consultants.

These simulations not only help you identify vulnerabilities in your applications but also allow you to test your response to these attacks. This can provide valuable insights into how well your overall security process addresses security threats, your ability to respond to incidents when they happen, and where improvements can be made.

5. Discover, Monitor, and Test APIs for Security

API security is a critical facet of best practices for application security testing. This comprehensive approach includes the initial step of automated discovery, ensuring every API, including often overlooked shadow APIs in production, is accounted. This phase is crucial as it sets the foundation for thorough security oversight. Continuous monitoring then plays a vital role, actively tracking any changes or additions to the API infrastructure, whether in development, testing, or staging phases. This is not just about passive observation; it's a proactive measure to spot potential vulnerabilities or breaches early in the development cycle.

Rigorous security testing of all APIs, conducted at every stage of the development lifecycle, is a cornerstone of this strategy. Such testing is crucial for identifying vulnerabilities early, a key aspect of the 'shift-left' methodology in software development. This methodology emphasizes integrating security measures from the very beginning of API development, thereby embedding a culture of security within the development process.

By conducting regular audits and assessments, organizations ensure that their API security measures are both current and effective against evolving cyber threats. Additionally, developer education on the risks associated with creating undocumented APIs and the importance of adhering to API governance policies can significantly reduce the occurrence of shadow APIs. By integrating these practices, organizations ensure that all APIs, whether official or shadow, are secure and comply with the organization's overarching security standards.

Learn more in our detailed guide to dynamic application security testing

Application Security Testing for APIs with Pynt

Pynt's focuses on API security, the main attack vector in modern applications. Pynt’s solution aligns with application security best practices by offering automated API discovery and testing, which are critical for identifying vulnerabilities early in the development cycle. It emphasizes continuous monitoring and rigorous testing across all stages, from development to production, ensuring comprehensive API security. Pynt's approach integrates seamlessly with CI/CD pipelines, supporting the 'shift-left' methodology. This ensures that API security is not just an afterthought but a fundamental aspect of the development process, enhancing overall application security.

Learn with Pynt about prioritizing API security in your AST strategy to protect against emerging threats and vulnerabilities.

See Additional Guides on Key Security Testing Topics

Together with our content partners, we have authored in-depth guides on several other topics that can also be useful as you explore the world of security testing.

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