Secure SDLC: Building Security Into Every Development Phase

A Secure Software Development Lifecycle (Secure SDLC) is a framework that integrates security activities into every phase of software development—from requirements gathering through design, implementation, testing, deployment, and maintenance. Rather than treating security as a final validation step, Secure SDLC makes it a continuous process that evolves alongside the application.

Frameworks like Microsoft SDL, NIST SP 800-64, and OWASP SAMM provide structured approaches to Secure SDLC. While they differ in specifics, all share a common premise: security defects are cheapest to fix when caught early. A vulnerability identified during design costs a fraction of one discovered in production, both in engineering time and business impact.

Secure SDLC is not a replacement for DevSecOps—it is the broader organizational framework within which DevSecOps automation operates. DevSecOps tooling enforces the technical security gates that Secure SDLC defines. Without the framework, tools run without context; without the tools, the framework remains aspirational.

Requirements

Define security requirements alongside functional requirements. Identify the data the application will handle (PII, financial, health records), applicable compliance standards (PCI-DSS, HIPAA, GDPR), and abuse cases that describe how an attacker might misuse each feature.

Design

Conduct threat modeling using frameworks like STRIDE or PASTA. Identify trust boundaries, data flows, and attack surfaces. Document security architecture decisions: authentication mechanisms, encryption schemes, access control models, and secrets management.

Implementation

Enforce secure coding standards with automated SAST tools that run on every commit and pull request. Scan dependencies with SCA to prevent introducing known-vulnerable packages. Detect hardcoded secrets before they reach version control.

Testing

Run DAST against the deployed application in staging. Execute security-focused test cases derived from threat models and abuse cases. Validate that security controls (authentication, authorization, input validation) function correctly under adversarial conditions.

Deployment and Maintenance

Generate SBOMs for every release to enable rapid vulnerability response. Monitor dependencies continuously for newly disclosed CVEs. Maintain incident response procedures tied to SBOM data so that when a zero-day is announced, affected deployments are identified within minutes.

Traditional SDLC treats security as a pre-release gate—a penetration test or security review conducted after development is complete. This approach fails for three reasons:

Late discovery, expensive fixes. Vulnerabilities found during a pre-release pen test require developers to revisit code they wrote weeks or months earlier. Context is lost, deadlines are compressed, and fixes are often rushed patches rather than proper remediations.

Incomplete coverage. A penetration test examines the running application from the outside. It cannot inspect every code path, configuration file, or dependency. SAST and SCA find vulnerability classes that DAST and pen testing miss entirely—hardcoded secrets, insecure deserialization, and vulnerable transitive dependencies.

Release velocity mismatch. Teams shipping daily or weekly cannot wait for periodic security reviews. Every release without automated checks is a release with unchecked risk. The traditional model was designed for quarterly releases, not continuous delivery.

CodeSlick automates the implementation and testing phases of a Secure SDLC with continuous security feedback:

• Implementation phase: The CLI pre-commit hook and GitHub App PR reviews enforce secure coding standards on every code change. 294 checks detect injection, secrets, insecure configurations, and vulnerable dependencies across 5 languages.
• Testing phase: SARIF output integrates with GitHub's Security tab for centralized vulnerability tracking. Pass/fail thresholds let teams define severity gates that block merges when standards are not met.
• Maintenance phase: SBOM generation in SPDX and CycloneDX formats provides the dependency inventory needed for continuous vulnerability monitoring and compliance audits.

All findings include CWE classification, CVSS scoring, and OWASP mapping, providing the traceability that Secure SDLC frameworks require.