7 principles of secure design in software development security

What does security by design in software development really mean?

Secure design in software development is a proactive approach to building applications with cybersecurity baked into every stage of a secure software development lifecycle (SDLC). It emphasizes gaining insight into potential vulnerabilities and addressing them during design, rather than patching issues post-deployment, to make security proactive instead of reactive. 

In web application security, secure design shifts the focus from reactive security measures to creating resilient systems from the ground up. Doing so is a step toward making sure that security is not treated as an afterthought but is integrated as a core function of the software. Whether it’s safeguarding sensitive data, preventing unauthorized access, or maintaining system integrity, secure design is about anticipating threats and mitigating them effectively.

Code vs. security: the security-by-design imperative

Traditionally, security and development have trade-offs that they must complete, and compromises can be tricky. Developers tend to lean towards prioritizing and delivering features, while security is relegated to a secondary concern. However, implementing this approach leads to costly breaches and technical debt.

In a security-by-design environment, security requirements are non-negotiable from the start. Developers and security teams work together early so that they can maintain innovation while also meeting compliance needs and safeguarding sensitive information through mitigation.

7 principles of secure design in software development

1. Security as code

Treat security mechanisms as code to ensure consistency and repeatability. When teams are able to automate security policies and embed them into CI/CD pipelines they have more scalable and efficient management for security risks. With infrastructure-as-code tools, configurations can be version-controlled, tested, and deployed securely.

2. Secure defaults

Systems should default to the most secure configurations. Making strong passwords mandatory, enforcing HTTPS, and preventing unnecessary access are all common examples of operating on secure defaults. When teams can minimize the need for manual intervention, secure defaults work to reduce human error and improve risk management.

3. Least privilege

Grant users and systems only the permissions they need to perform their tasks—nothing more. Ensuring least privileges in your security practices can help safeguard sensitive information and prevent damaging or costly breaches from security issues.

4. Separation of duties

Divide responsibilities to reduce the risk of abuse or error. By requiring multiple people or systems to approve critical actions, such as deploying changes to production, you create a system of checks and balances.

5. Minimize attack surface area

Every feature, endpoint, or service is a potential point of attack. By limiting the number of entry points, you make it much more difficult for attackers to exploit security vulnerabilities. This includes removing deprecated APIs, closing unused ports, and disabling unnecessary features.

6. Complete mediation

Every access request should be verified every time. Set in place controls that consistently validate the threats you find, and avoid caching with access permissions. This helps the team make sure changes in roles or privileges are enforced quickly and effectively.

7. Failing securely

When systems fail, they should default to a secure state. For instance, if an error occurs during authentication, access should be denied rather than granted. Designing for failure ensures that unexpected issues don’t compromise the overall security.

Secure Design and proactive defense with DAST (Dynamic application security testing)

Dynamic application security testing (DAST) plays a critical role in achieving secure software development by identifying vulnerabilities in running applications. Unlike static testing, which reviews code before execution, DAST can simulate attacks as they’re performed in the real world by analyzing an application and how it acts during runtime.

This approach follows security best practices and helps developers uncover security flaws that could only manifest when the application is operational, such as misconfigurations, authentication weaknesses, or input validation issues.

The role of DAST in secure design

Secure design principles and DAST go hand in hand because DAST actively tests an application’s attack surface during development and deployment. This means teams have a more proactive approach to security, with security baked into the very design of the application, especially when automation is a reliable feature. Here’s how it contributes:

Minimizing attack surface area

DAST tools identify unnecessary or vulnerable features that could be exploited by assessing the application’s interfaces, APIs, and endpoints. By reducing the attack surface, developers can eliminate weak points and reduce software vulnerabilities before malicious actors discover them and enact cyberattacks.

Failing securely

Testing how a web application behaves under various failure scenarios is a key feature of DAST. These tools simulate conditions like unexpected inputs or server errors to ensure the application defaults to a secure state, such as denying access or providing generic error messages that don’t expose sensitive information.

Secure defaults and least privilege

DAST identifies misconfigurations, such as excessive permissions or insecure default settings, that could leave applications exposed. For example, it can flag overly permissive API endpoints or configurations that bypass authentication requirements.

Proactive defense through continuous testing

Integrating DAST and coding standards into your development pipeline ensures vulnerabilities are identified and resolved in near real-time. Here’s how proactive DAST testing enhances secure software development:

Early detection of vulnerabilities

Builds can be scanned automatically before deployment when DAST tools are integrated into CI/CD pipelines. By taking this kind of proactive approach, vulnerabilities are caught sooner rather than later, and money is saved by fixing the root cause of potential data breaches.

Real-world attack simulation

DAST mimics attacker behavior by attempting exploits such as SQL injection, cross-site scripting (XSS), and other runtime vulnerabilities. These simulated attacks provide insights into how your application would perform under genuine threats.

Comprehensive Coverage Across Application Layers

DAST evaluates both the front-end and back-end of applications, uncovering issues in authentication, session management, and data handling processes that static analysis tools might miss.

Best practices for using DAST in secure software development

Integrate early and often

Embed DAST in your development lifecycle to ensure continuous monitoring and testing by development teams, practicing positive security awareness. Running scans during development, staging, and post-deployment phases ensures vulnerabilities are addressed promptly.

Combine DAST with other security tools

Use DAST alongside SAST (static application security testing) and IAST (interactive application security testing) to achieve a comprehensive security posture and reduce the likelihood of security breaches. This combination allows you to identify vulnerabilities in both code and runtime environments.

Remediate based on priorities

DAST tools often provide a severity ranking for identified vulnerabilities. Focus on resolving high-priority issues that pose the greatest risk to your application with potential security incidents.

Educate your team

Train developers on how to properly digest and interpret DAST findings, and on how to apply secure design principles when remediating those DAST findings. Doing so helps ensure that security insights are translated into proactive improvements and security standards are met.  

Enhancing proactive defense

By leveraging DAST and security controls in software development security, organizations can shift from a reactive to a proactive security approach. This aligns with secure software development by ensuring vulnerabilities are identified and mitigated during the development process, not after an attack occurs.

Not only is DAST a frontline defense against critical vulnerabilities, but also it provides feedback that can help developers align with secure design and secure coding practices. Incorporating DAST into your workflows enables you to build a resilient software application and a more secure software development lifecycle that stands strong against consistent security threats.