Application security is a critical component of modern cybersecurity, safeguarding applications from threats that can compromise data integrity, user privacy, and system stability. Organizations that fail to implement robust security measures expose themselves to cyberattacks, data breaches, and compliance violations.

To build a strong security foundation, application security relies on three essential pillars: secure software development, security testing, and runtime protection. These pillars work together to create a comprehensive security strategy that addresses vulnerabilities at every stage of an application’s lifecycle.

1. Secure software development

Building security into the development lifecycle

The first pillar of application security focuses on embedding security into the software development lifecycle (SDLC). Rather than treating security as an afterthought, secure software development ensures that security is integrated from the initial design phase through deployment.

Key aspects of secure software development:

1. Secure coding practices

Developers must follow secure coding guidelines to minimize vulnerabilities such as SQL injection, cross-site scripting (XSS), and buffer overflows. Organizations should adopt frameworks such as:

• OWASP Secure Coding Guidelines
• NIST Secure Software Development Framework (SSDF)

2. Threat modeling

Threat modeling helps teams identify potential attack vectors before writing code. This proactive approach ensures that applications are designed with security in mind. Common threat modeling methodologies include:

• STRIDE (Spoofing, Tampering, Repudiation, Information Disclosure, Denial of Service, Elevation of Privilege)
• DREAD (Damage, Reproducibility, Exploitability, Affected Users, Discoverability)

3. DevSecOps integration

DevSecOps embeds security into DevOps workflows, ensuring continuous security checks without slowing down development. Security automation tools that help identify security flaws early include:

• DAST (Dynamic Application Security Testing) tools
• SCA (Software Composition Analysis) tools, a.k.a. dependency scanners
• SAST (Static Application Security Testing) tools
  

Pro tip: Adopt a “shift left” approach. Security should start at early development stages rather than waiting until after deployment.

2. Security testing

Identifying and addressing vulnerabilities

Security testing validates whether an application can withstand real-world attacks. A combination of automated and manual testing techniques ensures that vulnerabilities are detected before attackers can exploit them.

Key security testing methods:

1. Dynamic Application Security Testing (DAST)

DAST tests applications at runtime, simulating attacks to identify security weaknesses in a live environment. Unlike SAST, it does not require access to source code. Two of the world’s leading DAST tools are Invicti and Acunetix by Invicti.

2. Static Application Security Testing (SAST)

SAST analyzes source code for vulnerabilities before the application is executed. This approach helps identify issues early in development but does not detect runtime vulnerabilities and is prone to false positives.

3. Interactive Application Security Testing (IAST)

IAST combines aspects of both SAST and DAST by analyzing applications during execution. IAST tools vary greatly, from products that rely on source code instrumentation to DAST-driven agent-based solutions that provide the scanner with real-time feedback on security issues while the application is running.

4. Penetration testing (ethical hacking)

Penetration testing involves skilled security professionals simulating real-world attacks to uncover vulnerabilities that automated tools may miss.

Pro tip: Combine multiple testing approaches. No single method catches all vulnerabilities. Using a mix of DAST, SAST, IAST, and penetration testing ensures comprehensive security coverage.

3. Runtime protection

Defending applications in a live environment

Even with secure development and rigorous testing, applications must have real-time protection to detect and mitigate attacks as they occur.

Key components of runtime protection:

1. Web Application Firewalls (WAFs)

A WAF filters, monitors, and blocks malicious traffic targeting web applications. It provides protection against common threats like SQL injection, XSS, and DDoS attacks.

2. Runtime Application Self-Protection (RASP)

RASP monitors applications in real-time and responds to threats inside the application itself rather than relying solely on external defenses.

3. API security & protection

With APIs becoming prime targets for attacks, organizations must secure API endpoints through:

• Authentication & Authorization (OAuth, JWT, API Keys)
• API Gateways (Kong, Apigee, AWS API Gateway)
• Rate Limiting & Anomaly Detection

4. Zero Trust security model

Zero Trust ensures that no request or user is automatically trusted, enforcing strict authentication and least privilege access controls.

Pro tip: Deploy layered security controls. Combining WAFs, RASP, and Zero Trust principles ensures applications are resilient against evolving threats.

FAQ: Application security

1. What are the three pillars of application security?

The three pillars of application security are:

• Secure software development—Incorporating security best practices into the development process.
• Security testing—Identifying vulnerabilities using methods like DAST, SAST, IAST, and penetration testing.
• Runtime protection—Defending applications in real-time with WAFs, RASP, API security, and Zero Trust models.

2. Why is secure software development important?

Secure software development ensures that security is integrated from the start, reducing vulnerabilities before an application goes live. It includes secure coding practices, threat modeling, and DevSecOps integration to build resilient applications.

3. What is the difference between DAST, SAST, and IAST in security testing?

• DAST (Dynamic Application Security Testing): Tests a running application by simulating real-world attacks.
• SAST (Static Application Security Testing): Scans source code before execution to detect vulnerabilities.
• IAST (Interactive Application Security Testing): Combines SAST and DAST to provide real-time security analysis during execution.

4. How does penetration testing differ from automated security testing?

Penetration testing is a manual security assessment where ethical hackers simulate real-world attacks to uncover vulnerabilities. Automated security testing (DAST, SAST, IAST) uses tools to scan applications for known security issues.

5. What is a Web Application Firewall (WAF), and why is it important?

A WAF protects web applications by filtering and blocking malicious traffic, preventing attacks like SQL injection, cross-site scripting (XSS), and DDoS. It acts as a barrier between users and an application’s backend.

6. How does Runtime Application Self-Protection (RASP) enhance security?

RASP provides real-time security by monitoring application behavior and automatically responding to threats within the application itself. Unlike traditional defenses, RASP detects and mitigates attacks from inside the app.

7. Why is API security a critical part of runtime protection?

APIs are prime targets for cyberattacks, often exposing sensitive data. API security measures like authentication (OAuth, API keys), rate limiting, and anomaly detection help protect APIs from unauthorized access and abuse.

8. What is the Zero Trust security model, and how does it apply to application security?

Zero Trust operates on the principle of “never trust, always verify.” It enforces strict access controls, requiring authentication and least privilege access for all users and systems, reducing attack surfaces.

9. How can organizations integrate security into their DevOps process?

Organizations can implement DevSecOps, where security is integrated into CI/CD pipelines using automated security scans, secure coding practices, and continuous monitoring to identify and remediate vulnerabilities early.

10. What is the best approach for ensuring comprehensive application security?

A layered security approach combining the three pillars—secure software development, security testing, and runtime protection—is the best strategy. Using a mix of secure coding, automated testing, real-time monitoring, and proactive defense mechanisms creates a resilient application security framework.

Conclusion: A holistic approach to application security

Application security is not just about fixing bugs or deploying firewalls—it requires a multi-layered approach that integrates secure development, rigorous testing, and real-time protection. By strengthening the three pillars of application security, namely secure software development, security testing, and runtime protection, organizations can minimize risks, prevent breaches, and build resilient applications.