Development, Security, Tech

Security Testing 101 for Application Developers

What Is Application Security Testing? 

Application Security Testing, or AST for short, is a critical part of the software development process that focuses on identifying, analyzing, and rectifying security vulnerabilities in software applications. With the increase in cyber threats, ensuring the security of applications has become a top priority for businesses worldwide.

AST involves a detailed examination of an application’s code, design, and execution environment to identify potential security vulnerabilities. It’s a proactive approach that allows developers to spot issues early in the development lifecycle, well before deployment. This minimizes the risk of a security breach, which could lead to data theft, financial loss, and serious damage to a company’s reputation.

The process of Application Security Testing encompasses a variety of techniques such as Static Application Security Testing (SAST), Dynamic Application Security Testing (DAST), and Interactive Application Security Testing (IAST). These methods help in identifying different types of vulnerabilities within an application. Each technique has its unique benefits and is used for specific purposes during the application development lifecycle.

Common Security Vulnerabilities in Applications 

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Injection Flaws

Injection flaws are one of the most common types of security vulnerabilities found in applications. They occur when an application sends untrusted data to an interpreter. Injection flaws can lead to serious consequences, such as data loss or corruption, lack of accountability, or denial of access.

It is essential to design applications in a way that prevents injection flaws. This can be achieved by using parameterized queries, using safe API, or by limiting the use of interpreters. Regular application security testing can help in identifying and fixing these vulnerabilities at an early stage.

Cross-Site Scripting (XSS)

Cross-Site Scripting (XSS) attacks occur when an application includes untrusted data in a new web page without proper validation or escaping. XSS allows attackers to execute scripts in the victim’s browser, which can lead to session theft, identity theft, or defacement of websites.

A robust application security testing process can help prevent XSS attacks. This involves implementing output encoding, input validation, and adopting a Content Security Policy (CSP). Regular security reviews and updates are also crucial to keep up with the evolving nature of XSS threats.

Cross-Site Request Forgery (CSRF)

Cross-Site Request Forgery (CSRF) is an attack that tricks the victim into submitting a malicious request. It uses the identity and privileges of the victim to perform an undesired function on their behalf. CSRF can lead to potential harm such as unauthorized changes in email address, password theft, and funds transfer.

To prevent CSRF attacks, developers can use unique tokens for each session and embed them in all form submissions. Implementing the same-site cookie attribute can also prevent CSRF attacks. Regular application security testing can help in identifying potential CSRF vulnerabilities in an application.

Insecure Direct Object References (IDOR)

Insecure Direct Object References (IDOR) occur when an application exposes a reference to an internal implementation object. Attackers can manipulate these references to gain unauthorized access to data. IDOR can result in unauthorized viewing of user accounts, alteration of data, and deletion of records.

AST can help detect IDOR vulnerabilities by thorough code review and testing all points of data exposure. Additionally, developers should avoid exposing direct references to internal objects and should implement access controls to confirm the user’s authorization before granting access to data.

Security Misconfigurations

Security misconfigurations can happen at any level of an application stack, including the platform, web server, application server, framework, and custom code. They can lead to unauthorized access to sensitive data or functionality, or even full system control.

Regularly updating and patching systems, removing unused features, and implementing least privilege principles can help prevent these vulnerabilities. Application Security Testing can identify security misconfigurations in applications and provide guidance on how to rectify them.

Insecure Deserialization

Insecure Deserialization flaws can enable an attacker to execute arbitrary code in the application’s context, leading to remote code execution, replay attacks, or injection attacks. These vulnerabilities occur when untrusted serialized objects are deserialized by an application.

To prevent insecure deserialization, developers should not deserialize data from untrusted sources and should implement integrity checks such as digital signatures on serialized objects. Regular application security testing can help identify insecure deserialization flaws and provide recommendations for mitigation.

Types of Application Security Testing Techniques 

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Application security testing techniques are the gatekeepers that ensure the safety of your application against potential threats. They follow a systematic approach to identify any vulnerabilities that could compromise the system. Let’s discover four main types of Application Security Testing techniques.

Static Application Security Testing

Static Application Security Testing (SAST), also known as white-box testing, is a testing technique that examines the application’s source code before it’s compiled. It enables developers to catch and fix security vulnerabilities early in the development process, making it an efficient and cost-effective method. SAST is typically used in the coding phase of the Software Development Life Cycle (SDLC) and can identify complex vulnerabilities like buffer overflows and input validation errors.

Dynamic Application Security Testing

Dynamic Application Security Testing (DAST), or black-box testing, is a technique that tests the application in its running state. Unlike SAST, DAST does not require access to the source code. Instead, it simulates attacks on the application to identify vulnerabilities that could be exploited when the application is live. DAST is ideal for detecting runtime errors, configuration issues, and server-side vulnerabilities.

Interactive Application Security Testing

Interactive Application Security Testing (IAST) is a blend of both SAST and DAST, providing the best of both worlds. IAST uses software instrumentation to monitor an application in its running state, observing the application’s interactions with inputs and its behavior. This approach allows IAST to detect both internal and external vulnerabilities with higher accuracy while reducing false positives.

Penetration Testing

Penetration testing, often referred to as ethical hacking, involves simulating cyber attacks on the application to identify vulnerabilities. A penetration tester will try to breach the application’s security defenses using the same techniques as a malicious hacker but with the intent to identify and fix the vulnerabilities, not exploit them. This method is highly effective in detecting real-world attack scenarios and evaluating the application’s resilience against such threats.

Implementing Application Security Testing 

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With the understanding of different application security testing techniques, let’s move forward to how developers can implement these tests in their development process.

Secure Coding

Secure coding should be the first line of defense in application security. It involves developing applications in such a way that they are resistant to security vulnerabilities. Developers should follow best practices like input validation, error handling, and secure session management. By adhering to secure coding standards, developers can significantly reduce the potential attack surface of an application.

Integrating Security into SDLC

Security should not be an afterthought in the development process. Instead, it should be integrated into each phase of the SDLC, from planning and design to testing and maintenance. This approach, known as Security Development Lifecycle (SDL), ensures that security considerations are taken into account at every step, leading to the development of more secure applications.

Using Automated Security Testing Tools

Automated security testing tools are instrumental in identifying security vulnerabilities in an application. These tools can perform tasks like code scanning, vulnerability scanning, and penetration testing in an automated manner, saving time and effort for developers. They also offer a high degree of accuracy and can detect complex vulnerabilities that may be missed in manual testing.

Security Code Reviews

A security code review is a systematic examination of the application’s source code to detect security flaws. This process can identify vulnerabilities related to insecure coding practices, configuration errors, and more. Security code reviews not only help in catching security issues early but also educate developers about secure coding practices.


Application Security Testing is a critical aspect of software development, essential for safeguarding applications against potential threats. By understanding and implementing the various types of AST techniques, integrating security into the SDLC, practicing secure coding, using automated security testing tools, conducting security code reviews, and fostering a culture of security awareness, developers can significantly enhance the security of their applications.

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