Adopting these principles from the start of a project leads to systems that are robust, resilient, and far less likely to suffer catastrophic breaches. “Secure by Design” is not a one-time checklist—it’s a mindset and an ongoing process. Embedding security at every SDLC stage ensures you’re not just building fast—you’re building safe. It shifts security “left,” making it more proactive, less costly, and less disruptive than fixing issues after the fact. Bake security into every phase—by design, by process, and by habit.

Cybersecurity expert Jeff Crume explores the 10 principles for secure by design, a best practice approach to building secure systems. Jeff discusses the importance of security by design, and how it can be achieved by following these 10 principles. From the principle of least privilege to secure by default, Jeff covers each principle in detail, providing examples and explanations to help you understand how to apply them.

10 Principles for Secure by Design

1. Secure Defaults

• Description: Out-of-the-box, systems should be secure. Features and settings should default to the safest, least-permissive options.

• Examples:

  • New users have minimal privileges by default.

  • Services are off unless explicitly enabled.

• Why: Most users never change default settings, so secure defaults minimize accidental exposure.

2. Least Privilege

• Description: Give users and programs the minimum access they need to do their jobs—nothing more.

• Examples:

  • An application cannot write to disk unless necessary.

  • Database users have only read access unless they require write/update.

• Why: Restricts the damage that can occur if an account or process is compromised.

3. Defense in Depth

• Description: Use multiple layers of security controls. If one is bypassed, others still protect you.

• Examples:

  • Firewall + authentication + encrypted data + monitoring.

  • Network segmentation + endpoint security + intrusion detection.

• Why: No single control is perfect; layers make attacks much harder.

4. Fail Securely

• Description: When systems fail, they should do so in a way that maintains security.

• Examples:

  • If authentication fails, access is denied—not granted.

  • Logging and error handling avoid leaking sensitive information.

• Why: Mistakes and outages shouldn’t accidentally open up security holes.

5. Separation of Duties

• Description: Split critical tasks and privileges so no one person or system has unchecked power.

• Examples:

  • The person who approves expenses can’t also issue payments.

  • Deployment and code review require different individuals.

• Why: Reduces the risk of insider threats and catches mistakes.

6. Keep It Simple

• Description: Simple designs are easier to secure and audit. Complexity breeds errors and hidden vulnerabilities.

• Examples:

  • Clear, understandable code.

  • Minimal dependencies and configurations.

• Why: Attackers exploit overlooked edge cases in complex systems.

7. Establish Secure Defaults for 3rd Party Components

• Description: When integrating third-party tools, libraries, or APIs, use their secure configurations and monitor their updates.

• Examples:

  • Disable unnecessary modules or plugins.

  • Apply security patches promptly.

• Why: Vulnerabilities often creep in via third-party components.

8. Secure the Supply Chain

• Description: Vet the security of all code, dependencies, and services you use—don’t just trust them blindly.

• Examples:

  • Scan dependencies for vulnerabilities.

  • Use signed packages and verify authenticity.

• Why: Supply chain attacks are rising; a weak link can compromise your entire system.

9. Continuous Monitoring and Logging

• Description: Always monitor systems for suspicious activity and maintain audit logs.

• Examples:

  • Centralized log aggregation and alerting.

  • Automatic anomaly detection.

• Why: Rapid detection helps minimize damage and provides forensic evidence.

10. Plan for Breach and Recovery

• Description: Assume breaches are inevitable; have clear processes for incident response, containment, and recovery.

• Examples:

  • Regular backups and tested recovery plans.

  • Documented incident response playbooks.

• Why: Fast, organized response limits damage and downtime.

10 Principles for Secure by Design in the SDLC

1. Security Requirements Upfront

• Description: Identify and document security requirements from the very start—during planning and requirements gathering.

• Examples:

  • Include security user stories or acceptance criteria.

  • Define compliance, privacy, and threat model requirements.

• Why: Sets a security foundation for all later phases.

2. Threat Modeling Early and Often

• Description: Systematically analyze potential threats, risks, and attack vectors as part of architecture and design.

• Examples:

  • Use STRIDE, DREAD, or similar frameworks.

  • Regularly update threat models with design changes.

• Why: Helps you proactively design controls, not reactively patch.

3. Secure Design Reviews

• Description: Evaluate architecture and design for security issues before code is written.

• Examples:

  • Formal security design reviews.

  • Architecture diagrams annotated with security controls.

• Why: Prevents expensive and difficult-to-fix issues later.

4. Secure Coding Practices

• Description: Mandate use of secure coding standards and training for all developers.

• Examples:

  • Use OWASP Top 10 as a baseline.

  • Enforce secure code patterns and avoid anti-patterns.

• Why: Reduces introduction of common vulnerabilities.

5. Automated Security Testing

• Description: Integrate security testing into CI/CD pipelines.

• Examples:

  • Static code analysis (SAST), dynamic analysis (DAST), dependency scanning.

  • Security linting tools.

• Why: Early detection and remediation, with less manual effort.

6. Peer Code Reviews with Security Focus

• Description: Require peer code reviews that include checks for security issues—not just functionality.

• Examples:

  • Security checklists for reviewers.

  • Flag insecure patterns or missing validations.

• Why: Human eyes can catch logic flaws that tools miss.

7. Vulnerability Management and Patch Process

• Description: Establish processes for tracking, fixing, and deploying patches for discovered vulnerabilities.

• Examples:

  • Timely update of dependencies and libraries.

  • Documented patch timelines and communication plans.

• Why: Reduces window of exposure and builds customer trust.

8. Secure Configuration Management

• Description: Manage application and infrastructure configurations securely and track changes.

• Examples:

  • Use configuration-as-code (e.g., Terraform, Ansible).

  • Store secrets securely (vaults, environment variables).

• Why: Prevents insecure settings from being introduced or lingering.

9. Continuous Monitoring and Logging

• Description: Ensure the software supports robust logging and is instrumented for monitoring from the outset.

• Examples:

  • Application logs capture authentication, access, and errors.

  • Integrate with SIEM tools for alerting.

• Why: Enables rapid incident detection and response.

10. Security in Maintenance & Decommissioning

• Description: Apply security updates and securely retire or decommission systems at the end of their lifecycle.

• Examples:

  • Remove sensitive data and credentials during shutdown.

  • Ensure secure data destruction.

• Why: Prevents forgotten or abandoned systems from becoming attack surfaces.

TL;DR: 10 Principles for Secure by Design

1. Secure Defaults: Systems start with the safest settings.

2. Least Privilege: Users/programs get only the access they need.

3. Defense in Depth: Use layers of security controls.

4. Fail Securely: Systems remain secure even when things go wrong.

5. Separation of Duties: Split responsibilities to prevent abuse.

6. Keep It Simple: Simpler systems are easier to secure.

7. Secure 3rd Party Components: Harden and update everything you integrate.

8. Secure the Supply Chain: Vet and monitor all dependencies.

9. Monitoring and Logging: Continuously watch and record system activity.

10. Plan for Breach & Recovery: Be prepared for incidents and recovery.

TL;DR: Secure by Design Principles for SDLC

1. Security Requirements First: Define security goals from the start.

2. Threat Modeling: Regularly identify and plan for risks.

3. Design Reviews: Catch security flaws before coding.

4. Secure Coding: Enforce safe code practices.

5. Automated Security Testing: Integrate security checks into builds.

6. Security-Focused Code Reviews: Review code for security, not just bugs.

7. Vulnerability Management: Patch and update promptly.

8. Secure Configuration: Manage settings and secrets carefully.

9. Monitoring & Logging: Instrument systems for detection and response.

10. Secure Decommissioning: Safely retire and clean up old systems.