version: "1.0.1" name: secure-by-design description: > Apply Secure by Design, by Default, and in Deployment (SD3) principles. Use when reviewing default configurations, setup processes, update mechanisms, or evaluating whether a system fails open or closed. metadata: category: secure_development subcategory: security-principles

Secure by Design, by Default, in Deployment (SD3)

Principle: The default settings of a system or application are configured with strong security measures in place. Systems should be configured in a least-privilege model so that no unnecessary services, daemons, or accounts are enabled.

Secure Default Configurations

• Ship products with secure defaults that protect users without requiring manual hardening
• Generate unique keys and secrets during first run or installation, not at build time
• Encourage users to review and customize settings, but ensure the uncustomized state is safe
• Minimizes risk from users or administrators who overlook or delay security configuration

Fail Secure

• Design services to fail closed: when they fail, they deny access rather than granting it
• A security service that cannot be reached must result in a denied request, not an open door
• Apply this to authentication, authorization, input validation, and configuration loading

Secure Baselines

• Create server and application security baselines as reference configurations
• Deploy new systems from these baselines to ensure consistency
• Systems adhering to baselines are less vulnerable and require less ongoing maintenance

Encryption and Authentication by Default

• Enable encryption (TLS) and authentication by default, not as opt-in features
• Use HTTPS as the default communication protocol
• Protect data in transit and at rest as a baseline, not an upgrade

No Hardcoded Credentials

• Never use hard-coded secrets, default passwords, or static account credentials in code
• Generate unique credentials at deployment time
• Use secrets management systems (Vault, AWS Secrets Manager, etc.)

Default Deny Policies

• Only explicitly allowed actions are permitted
• No unnecessary services, daemons, or network ports are enabled
• Default network policies deny all traffic; allow rules are added explicitly

Code Integrity and Updates

• Use digital signatures and cryptographic hashes to verify the integrity and authenticity of software updates
• Implement automated update mechanisms to reduce the window of vulnerability
• Test patches thoroughly before deployment
• Secure the update infrastructure itself with access controls and monitoring

Implementation Checklist

• [ ] Default configuration is secure without manual hardening
• [ ] Unique secrets are generated at first run or installation (not hardcoded)
• [ ] Service failures result in denied access (fail closed), not open access
• [ ] TLS and authentication are enabled by default
• [ ] HTTPS is the default protocol for all communication
• [ ] No hardcoded credentials exist in the codebase
• [ ] Default network policies deny all traffic; allow rules are explicit
• [ ] Unnecessary services, ports, and accounts are disabled by default
• [ ] Software updates are signed and verified before installation
• [ ] Update infrastructure is secured with access controls and monitoring
• [ ] Security baselines exist and new deployments are built from them