Certified: The CISSP Prepcast

Welcome to The Bare Metal Cyber CISSP Prepcast. This series helps you prepare for the ISC squared CISSP exam with focused explanations and practical context.
In today’s episode, we’re diving into Software Development Lifecycle Models, often referred to as S D L C frameworks. These models are essential for structuring how software is planned, developed, tested, and deployed. But more than that, they define the rules and checkpoints that allow security to be built into the software from day one. Whether your organization is building web apps, mobile services, cloud-based tools, or internal utilities, a well-defined S D L C helps reduce vulnerabilities, control costs, and ensure consistent, reliable delivery. As a Certified Information Systems Security Professional, you’ll be expected to understand the major types of S D L C models, how they operate, and how to integrate security throughout every phase of development.
Let’s begin by defining what we mean by the Software Development Lifecycle. The S D L C is a structured set of phases that guide the creation of software—from initial planning and requirements gathering to design, development, testing, deployment, and maintenance. These phases are not just about engineering—they also represent opportunities to embed security and quality assurance into the software product.
Effective S D L C frameworks offer a roadmap for creating secure, stable, and functional applications. They reduce development risk by promoting consistency, setting expectations, and clarifying responsibilities. They also ensure that requirements are understood, code is tested, vulnerabilities are addressed, and deployment processes are smooth and repeatable.
By integrating security controls into each phase of the S D L C, organizations can prevent vulnerabilities from being introduced in the first place—rather than trying to fix them later when it’s more expensive and time-consuming.
Understanding how the S D L C works and how it supports secure development is a fundamental competency for professionals managing cybersecurity in any development-heavy environment.
Let’s now take a look at some of the most common S D L C models. First is the Waterfall Model. This is a linear and sequential approach where each phase of the development process is completed before the next begins. Requirements are defined up front, and phases such as design, implementation, and testing occur in a fixed order. The Waterfall Model is best suited for projects where requirements are well understood and unlikely to change. However, it can be rigid and slow to adapt if changes are needed later in the process.
Second is the Agile Model. Agile is an iterative, collaborative framework that emphasizes short development cycles, or sprints, with frequent feedback, testing, and adjustments. Agile supports rapid development and continuous delivery, making it ideal for dynamic environments. Agile also supports better alignment between developers and stakeholders through regular communication and quick iterations.
Third is the V-Model, also known as the Verification and Validation Model. It’s a structured and disciplined approach where development phases are directly linked to corresponding testing phases. For example, during the design phase, a parallel test plan is developed. This ensures validation and testing are integrated early and at every level. The V-Model offers strong quality control but requires careful planning.
Fourth is the Iterative Model. This approach emphasizes building a system incrementally through repeated cycles. Each iteration includes planning, design, implementation, and testing, allowing teams to refine requirements and improve functionality with each cycle. Iterative models are particularly effective when working on large or complex systems that benefit from regular refinements.
Understanding these models allows you to select or support the right approach based on your organization’s needs, your regulatory environment, and the flexibility required in your development processes.
Let’s now shift focus to the importance of secure S D L C. Secure S D L C means integrating security best practices into every phase of the development lifecycle—not just waiting until the software is built to start testing for vulnerabilities.
Secure S D L C begins with defining security requirements alongside functional ones. This might include specifying encryption standards, authentication mechanisms, or regulatory compliance requirements like those found in the Payment Card Industry Data Security Standard or General Data Protection Regulation.
During design, security architecture and threat modeling are applied to identify risks and define controls. During development, secure coding practices are enforced to prevent vulnerabilities such as buffer overflows, injection attacks, or data leakage. During testing, specialized tools such as static analysis, dynamic testing, and fuzz testing are used to validate security controls.
Deployment should include secure configuration, access control, and monitoring. And during maintenance, ongoing vulnerability scanning and patch management keep the software secure throughout its lifecycle.
The benefits of a secure S D L C are substantial. It reduces vulnerabilities, lowers the cost of remediation, improves user trust, and helps meet compliance requirements. Organizations that invest in secure development see fewer breaches, faster response times, and stronger software quality overall.
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Now let’s walk through how to implement effective S D L C practices. Start by documenting your development processes. This includes defining the phases, the stakeholders involved, their responsibilities, and the security activities required at each stage. Clearly identify where security reviews, testing, and approvals must occur.
Establish secure coding standards. These standards provide rules for developers to follow when writing code, helping prevent common vulnerabilities. Refer to resources such as the O W A S P Secure Coding Guidelines or S A N S Top Twenty Five to shape your policies.
Incorporate testing into every stage. Use tools such as Static Application Security Testing—also called S A S T—for analyzing source code without executing it. Combine this with Dynamic Application Security Testing—known as D A S T—which tests running applications from the outside. Penetration testing should be used before deployment to validate the effectiveness of controls.
Conduct security reviews and code audits regularly. Bring in independent reviewers or red teamers to evaluate designs, check for risky configurations, and suggest architectural improvements.
Train everyone involved in development—including developers, project managers, quality assurance teams, and security professionals. Secure development is a team effort, and every member must understand their role and responsibilities within the S D L C.
Let’s now examine the security controls that support S D L C management. Begin with secure development tools and platforms. Use integrated development environments that support secure plug-ins, secure code repositories with version control, and collaboration tools that enforce access control.
Apply security scanning tools within the development pipeline. Automated tools should scan for insecure dependencies, hardcoded secrets, or misconfigured components as part of your build process. Make security part of your Continuous Integration and Continuous Deployment strategy.
Use encrypted communications and secure data handling practices. Whether developers are accessing source code or transferring builds to testing environments, data in transit and at rest must be protected.
Conduct regular assessments and audits. These should evaluate your S D L C workflows, validate the use of secure development practices, and ensure that documentation is up to date and accurate.
Maintain records. This includes requirements, test cases, vulnerability reports, developer training records, and deployment approvals. Documentation supports compliance, traceability, and forensic readiness in the event of an incident.
Let’s wrap up with continuous improvement in S D L C management. Software development never stands still—and neither should your security processes. Regularly review your methodology in light of new threats, programming languages, frameworks, and legal obligations.
Use feedback from development teams, security analysts, and quality assurance testers to refine your practices. After each release, conduct a post-mortem to capture lessons learned and adjust your strategy.
Collaborate across disciplines. Involve business units, legal teams, compliance officers, and users in the planning and improvement of development practices. Their insights can improve security, usability, and alignment with organizational goals.
Keep training ongoing. New tools, vulnerabilities, and coding techniques are always emerging. Provide refresher courses, workshops, and certification paths for developers and security professionals.
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