The seven phases of the software development life cycle (SDLC)

There are many SDLC models in use today, each with its own distinct advantages and limitations. Some SDLC approaches incorporate the agile methodology, which allows for more flexibility and incremental iteration, while others rely on the more linear and sequential waterfall methodology.

Each SDLC framework tends to consist of between five and seven distinct phases, depending on the company involved and its specific goals for software development. The core SDLC phases are usually concerned with software design, development, testing, and deployment.

Here are the seven most common phases found in an SDLC approach:

1. Planning. Product and project managers convene to discuss the scope of the project. At this stage, they may create early written deliverables such as project plans, schedules, cost estimates, and procurement requirements.
2. Requirements. Technology professionals begin gathering requirements from business stakeholders. If a previous system exists, they examine its deficiencies and identify any remediations that need to be addressed in the new version. If the software will be brand-new, they will simply proceed toward defining its requirements. In either case, the goal is to create a detailed definition of what the end product is intended to achieve.
3. Design and prototyping. Software developers convert the requirements they have gathered into a software design plan. They outline the software’s architecture and specify the technologies involved in its development as well as the team resources, time frames, and budget that are required to create it.
4. Development. Developers create the software, engaging stakeholders to confirm that it fulfills the desired requirements. At the completion of this phase, the business should have functional software that can then be tested and deployed.
5. Testing. This crucial phase of the SDLC focuses on ensuring a quality product, employing a range of testing methods including code quality, unit testing, integration testing, performance testing, and security testing to ensure the software performs as expected. Flaws or bugs that were not detected in the development stage are examined and remediated before the final product proceeds to deployment.
6. Deployment. After all issues have been fixed, the software is placed into production. This process is automated in some larger enterprise environments, whereas some midsize and smaller organizations or businesses in exceptionally regulated industries may require additional final sign-off steps before this phase is complete.
7. Operations and maintenance. After the software has been deployed, it is continually monitored for potential bugs, defects, or security vulnerabilities. This phase can loop back into earlier steps of the SDLC as the software, now in production, is continually refined and improved.

Application security and the software development life cycle (SDLC) 

While businesses often want to get new code out as quickly as possible in order to maximize opportunities in the market, this strategy sometimes fails to properly account for security concerns. Some businesses may discover unintended vulnerabilities that have the potential to gravely compromise their own corporate data as well as that of their clients. Some of the most severe breaches that have appeared in newspaper headlines in recent years have occurred because the businesses involved have not adequately prioritized security concerns early enough in the SDLC.

As awareness of the importance of application security has increased in recent years, more companies have begun factoring security concerns earlier into the SDLC. In doing so, they can better mitigate potential risks, detect bugs sooner, identify user experience problems earlier, and lower the costs involved with remediating all of these issues later on in the software development process. DevSecOps, a security-focused evolution of the popular DevOps concept of software design and deployment, seeks to explicitly embed application security best practices earlier into the SDLC.

Three tips for success with the software development life cycle

Address security early on. Cybercriminals are increasingly targeting web applications, so businesses must prioritize security concerns earlier in the SDLC. This is especially true if the software in question is mission-critical. Tapping the benefits of a web application security scanner and conducting other forms of web application security testing earlier in the process helps your business reduce risk, resolve emerging issues before they become major headaches, and cut costs.

1. Consider a DevSecOps approach. Application security should be a shared responsibility across your security, IT operations, and development teams rather than an afterthought relegated to a single team toward the end of the SDLC (often in the testing phase, as listed above). Moving application security left in the SDLC helps you securely deploy software without compromising on speed.
2. Encourage collaboration. Effective collaboration is crucial, especially when not everyone involved speaks the same language or views issues from the same lens. For example, security teams consider vulnerabilities major threats to the business, while their developer counterparts tend to chiefly view them as bugs to be fixed. Creating common tools and workspaces where the various teams can come together and collaborate, discuss issues early on, and foster a spirit of camaraderie will go a long way toward ensuring SDLC success.

The SDLC is an effective methodology for designing and creating software, but it especially shines when all stakeholders prioritize security concerns and thoughtfully weave security testing early into the process. By taking a security-conscious approach to your SDLC and encouraging effective collaboration among your teams, your business can bring high-quality software to market in less time and with fewer headaches along the way.

Dynamic Application Security Testing

Web Application Firewall (WAF)