ISO 27001 Control 8.25: Secure Development Life Cycle

Implementing a Secure Development Life Cycle

In today's digital landscape, secure software and system development is essential to maintaining the confidentiality, integrity, and availability of information assets.

A structured Secure Development Life Cycle (SDLC) ensures that security is embedded throughout the development process, reducing vulnerabilities and mitigating risks from the outset.

Establishing and enforcing secure development practices enables organisations to build resilient architectures, applications, and services while complying with regulatory and industry standards. Secure development is not just about preventing security breaches but also about ensuring that applications remain robust against evolving threats and business risks.

This article explores the key principles of the Secure Development Life Cycle as outlined in ISO/IEC 27001, including best practices for security integration, testing, version control, and developer training.

Purpose of a Secure Development Life Cycle

A Secure Development Life Cycle (SDLC) aims to:

• Embed Security Early – Integrate security from the design phase to prevent vulnerabilities.

• Enhance Software Resilience – Reduce security risks and strengthen application robustness.

• Ensure Compliance – Align with industry regulations and security standards.

• Protect Sensitive Data – Implement safeguards to prevent data breaches.

• Improve Developer Awareness – Provide security training to identify and mitigate risks.

• Reduce Costs of Fixing Vulnerabilities – Addressing security risks early in development is far more cost-effective than fixing issues post-deployment.

• Establish a Security Culture – Ensuring that security is a fundamental part of software development processes.

Key Components of a Secure Development Life Cycle

To effectively implement a secure SDLC, organisations should consider the following components:

1. Separation of Development, Test, and Production Environments

Keeping development, testing, and production environments separate minimises risks such as accidental data leaks, unauthorised access, and deployment errors. Each environment should have:

• Strict access controls and least privilege permissions.

• Secure data handling policies to prevent exposure of sensitive information.

• Isolated infrastructure to prevent unauthorised crossover between environments.

• Monitoring and logging to track environment changes and ensure compliance.

2. Security in the Software Development Methodology

Security should be embedded in the organisation's development methodology, whether Agile, DevSecOps, or Waterfall. This includes:

• Incorporating security requirements in the early design phase.

• Implementing secure coding guidelines for each programming language.

• Performing regular security reviews and risk assessments at each stage.

• Embedding automated security checks in the CI/CD pipeline.

3. Secure Coding Practices

To prevent common vulnerabilities such as SQL injection, cross-site scripting (XSS), and buffer overflows, developers should adhere to secure coding standards.

Best practices include:

• Using parameterised queries and input validation.

• Avoiding hardcoded credentials and secrets.

• Implementing error handling to prevent information leakage.

• Conducting peer reviews and automated static code analysis.

• Using secure frameworks and libraries to avoid known vulnerabilities.

4. Security Requirements in Specification and Design

Security must be defined at the specification and design stage, ensuring that:

• Security principles such as least privilege and defence-in-depth are applied.

• Threat modelling is conducted to identify potential risks.

• Secure authentication and access controls are designed into applications.

• Privacy-by-design principles are incorporated to ensure compliance with regulations such as GDPR.

5. Security Checkpoints in Development Projects

Security should be a mandatory checkpoint within development projects, ensuring:

• Regular security assessments and code reviews.

• Automated security scanning in CI/CD pipelines.

• Tracking of security findings and remediation efforts.

• Security champions embedded within development teams to promote security best practices.

6. System and Security Testing

Robust security testing ensures that applications remain resilient against attacks.

This includes:

• Regression Testing – Ensuring new code changes do not introduce vulnerabilities.

• Code Scanning – Using static and dynamic analysis tools to detect weaknesses.

• Penetration Testing – Conducting simulated attacks to identify exploitable flaws.

• Fuzz Testing – Identifying software crashes and unexpected behaviour.

• Runtime Application Self-Protection (RASP) – Implementing security controls that monitor applications in real time.

7. Secure Repositories and Version Control

Managing source code securely is essential to prevent unauthorised modifications or data leaks.

Best practices include:

• Using private and access-controlled repositories (e.g., Git, Bitbucket, Azure DevOps).

• Enforcing multi-factor authentication (MFA) for repository access.

• Implementing commit signing and code integrity verification.

• Automating dependency tracking and ensuring third-party libraries do not introduce vulnerabilities.

8. Security in Version Control

Effective version control practices help maintain secure and stable software. Security measures should include:

• Enforcing signed commits to verify the integrity of code contributions.

• Preventing exposure of sensitive data in commit history.

• Using access controls to restrict modifications to critical files.

• Implementing audit logging for code changes and security events.

9. Developer Security Training and Awareness

Continuous security education is crucial for developers to stay ahead of evolving threats. Training should cover:

• Secure coding techniques and OWASP Top 10 vulnerabilities.

• Secure software design principles and best practices.

• Recognising and responding to security incidents.

• Secure API development and data handling practices.

• Awareness of software supply chain security risks.

10. Managing Licensing Requirements

To avoid legal and financial risks, organisations should:

• Use open-source and commercial software within licensing compliance.

• Regularly audit software dependencies for security and licensing risks.

• Consider alternatives that balance cost and security needs.

• Implement automated tools to monitor licensing compliance.

Ensuring Secure Outsourced Development

If development is outsourced, organisations must ensure that third-party providers comply with secure development requirements.

This includes:

• Contractually enforcing secure development practices.

• Requiring security certifications and regular audits.

• Implementing third-party code review and security testing.

• Establishing clear security requirements in service-level agreements (SLAs).

Other Considerations

Secure development is not limited to software engineering but extends to:

• Embedded systems and IoT – Ensuring firmware security and secure hardware development.

• Scripting and automation – Securely developing scripts within applications, browsers, and databases.

• Cloud-native applications – Integrating security into containerised and serverless architectures.

• Mobile application security – Implementing best practices for securing Android and iOS applications.

Conclusion

A Secure Development Life Cycle is essential for building resilient software and systems. By embedding security at every phase of development, organisations can reduce vulnerabilities, protect sensitive data, and ensure compliance with industry standards.

Implementing secure development best practices, conducting thorough testing, and training developers on security principles will enhance overall cybersecurity posture and reduce the risk of security breaches. With continuous improvements and adherence to best practices, organisations can create robust, secure applications that withstand evolving threats. As cyber threats continue to advance, a proactive approach to secure development will be the foundation of a strong, resilient digital infrastructure.