Software Development Life Cycle (SDLC)

What is the software development life cycle?

The Software Development Life Cycle (SDLC) is a framework that defines activities performed throughout the development process. Think of it like a tool belt.

Product by software development life cycle (SDLC) phase

Software Development Life Cycle Phases


This is the first stage of any Software Development Life Cycle model. The project objective is determined during this stage. The client and company developing the software decide if they should keep the existing system as is, if changes are necessary, or if there is a need for new software. In the event that there is a need for new software, an estimate of resources (e.g., people, cost, etc.) is established. This information is then assembled into a project plan and submitted for management approval.

At Synopsys, we offer several recommended tools during the planning stage to ensure that both software quality and security are rock-solid:

  • Software Security Initiative In-a-Box (SSIB). Supplies everything you need to launch your software security initiative.
  • Building Security In Maturity Model (BSIMM). Measures your software security stance.
  • Maturity Action Plan (MAP). Offers recommendations to improve your software security stance.
  • Software Testing Optimization. Helps your team prioritize and create the right level of security testing.


The stakeholders, system users, and developers meet during this stage to decide the requirements of the application they are building. The goal is for everyone to understand each software requirement and the scope of work. Questions that require answers during this stage of the SDLC include:

  • Who will use the system?
  • How will they use the system?
  • What will the input be for the system?
  • What will the output be for the system?

At Synopsys, we offer several recommended tools during the design stage to ensure that both quality and security are rock-solid:


Crafting a high-level design of the software build is the primary objective of the third SDLC stage. Decisions are made about hardware and software required to build the product, in addition to the system architecture. Engineers produce meta-data and data dictionaries, logical diagrams, data-flow diagrams, and pseudo codes (when applicable). A design specification document (DSD) records this information.

At Synopsys, we offer several recommended tools during the implementation stage to ensure that both quality and security are rock-solid:


Within this stage, engineers code the software as per the established planning and design. The front-end, back-end, and the connection between the two are created during what is often the longest stage of the SDLC.

At Synopsys, we offer several recommended tools during the verification stage to ensure that both quality and security are rock-solid:

  • SAST / SCA. Hunts down any remaining bugs in the custom code, OSS, or third-party software.
  • IAST. Automates IAST testing into your CI/CD processes.
  • Dynamic Application Security Testing (DAST). Dynamically tests your applications before release.
  • Fuzz Testing. Ensures the integrated code can properly handle malformed inputs.
  • Penetration Testing. Manually hacks your app and resolve any weaknesses before it goes live.


The release stage ensures that the software requirements are in place, tested, and that the software works as expected. In the event that a defect is identified, testers inform the developers. If the defect is valid, developers resolve it and create a new version of the software which then repeats the testing during this stage. The cycle continues until all defects are mitigated and the software is ready for deployment into the production environment.

At Synopsys, we offer several recommended tools during the release stage to ensure that both quality and security are rock-solid:

  • DAST. Uncovers any new bugs when the app is running.
  • Network penetration testing. Certifies that the network configuration is secure.
  • Penetration testing. Contemplates the impacts of a potential attack.


Once there are no issues present within the software and it has been released into the production environment, customers test the software (also known as beta testing). Any bugs identified within this stage go to the engineering team for resolution.

The final deployment takes place once all bugs are resolved. Once the software moves into production, the maintenance team monitors the software’s performance and continuously evaluates it. If there are any issues in production, the team works to mitigate them immediately.

At Synopsys, we offer several recommended tools during the response stage of the SDLC to ensure that both quality and security are rock-solid:

  • Insider Threat Detection. Tests how easily your software can be breached.
  • Red Teaming. Explores how prepared your organization is to prevent and respond to incidents.

Building security into the DevOps lifecycle

Get actionable insight into building security into your DevOps SDLC.

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What are the top software development methodologies in use today?

The Waterfall Methodology

Waterfall presents the oldest, simplest, and most structured SDLC methodology. Each phase depends on the outcome of the previous phase and runs sequentially.

Advantages of the Waterfall Methodology. This model provides discipline and gives a tangible output at the end of each phase. Once the scope is defined, establishing and managing a timeline is straightforward.

Disadvantages of the Waterfall Methodology. This model doesn’t work well when flexibility is a requirement. There is little room for change once a phase is deemed complete. Changes made in the scope can impact cost, time, and quality of the software. Additionally, if tasks aren’t carried out properly in each stage, or if new tasks require attention at a later stage, the entire project has a severe impact.

The Agile Methodology

The Agile model is widely considered to be a realistic approach for development. It is an interactive approach in which the various phases operate in parallel. Most notably, Agile provides a working product quickly by breaking the product into cycles.

Advantages of the Agile Methodology. The Agile model emphasizes interaction as customers, developers, and testers coordinate throughout the project. Due to the model’s interactive nature, changes are easily brought into the process. It’s a transparent approach for tracing progress. Additionally, each iteration provides helpful feedback on the product.

Disadvantages of the Agile Methodology. Clear and thorough foundational requirements about product direction are critical. If the foundational requirements change often, planning becomes complicated and the project can go awry. Team members must be highly cross-skilled since core teams are often small. Team members must also be up-skilled on the chosen Agile framework.

Other SDLC models include the V-shaped model, the iterative model, and the spiral model. These are variations of the Waterfall and Agile models with similar advantages and disadvantages.

What is the secure software development life cycle (SSDLC)?

In the past, the common practice was to perform security-related activities only during testing. This after-the-fact technique often results in a high number of issues discovered too late (or not at all). It’s a far better practice to integrate activities across the SDLC. This helps discover and reduce vulnerabilities early—effectively building security in.

It is in this spirit that the concept of the Secure Software Development Life Cycle (SSDLC) arises. The secure software development life cycle process ensures that security assurance activities (e.g., penetration testing, code review, and architecture analysis) are an integral part of the development effort.

Generally speaking, the SSDLC is set up by implementing security-related activities within an existing development process. Examples include writing security requirements in coordination with the collection of functional requirements, or performing an architecture risk analysis during the design phase of the SDLC.

There are multiple SSDLC models in existence. Examples include:

  • MS Security Development Lifecycle (MS SDL): One of the first of its kind, Microsoft proposed the MS SDL in association with the phases of a classic SDLC.
  • NIST 800-64: Provides security considerations within the SDLC. Standards were developed by the National Institute of Standards and Technology for US federal agencies.

What are some key secure SDLC advantages?

The primary advantages of pursuing a SSDLC approach include:

  • More secure software due to the fact that security is a continuous concern.
  • Stakeholder awareness of security considerations.
  • Early flaw detection in the system.
  • Cost reduction as a result of early detection and resolution of issues.
  • Overall reduction of intrinsic business risks for the organization.