A quick guide to telling apart SSDLC, SDLC, SDL, and the security life cycle

Key takeaways

 

• A secure software development life cycle (SSDLC) and the security life cycle are easily confused but distinct terms.
• SSDLC denotes how an organization integrates security into its overall software development process, while the security life cycle refers to the process of implementing layered security controls into an organization.
• Implementing a successful SSDLC requires security testing to be integrated into the development pipeline, including solutions for dynamic application security testing (DAST).

There’s no shortage of cybersecurity terminology and acronyms, and maintaining fluency in the fast-moving space can be a challenge. Two concepts in particular – the secure software development life cycle (SSDLC) and the security life cycle – are especially tricky to distinguish since they sound alike and are both frequently used in cybersecurity. Adding to the confusion, SSDLC is often mistakenly used interchangeably with acronyms such as SDL (security development life cycle) and SDLC (software development life cycle).

In fact, SSDLC, security life cycle, and SDL are all distinct terms. Understanding their differences is crucial for any organization seeking to effectively integrate security into the software development processes while also defining information security controls.

SSDLC vs. security life cycle vs. SDL

SSDLC is an approach to software design and development that embeds security considerations throughout the development process. Referring generally to processes for producing secure software by design, SSDLC stresses the integration of security best practices into all phases of the SDLC – from requirements gathering and design to testing and implementation. The goal of an effective SSDLC is to prevent the introduction of vulnerabilities into software as it is developed and maintained by incorporating key application security practices at relevant stages of the SDLC, such as threat modeling, secure coding practices, and security testing.   

The similarly named security life cycle (also referred to as security life cycle management) encompasses the efforts an organization takes to protect its corporate networks, systems, and data. A security life cycle typically includes perimeter protection, risk and vulnerability assessment, application security policies, penetration testing, and intrusion detection. The SSDLC often falls under the category of application security policies within an organization’s broader security life cycle.

Further complicating matters, those who work in software development will likely come across another term: security development life cycle, or SDL. This is a specific approach to building an SSDLC that was first defined and used internally by Microsoft to identify and mitigate vulnerabilities in its own software (hence you will also see it called MS SDL). The SDL has been a mandatory practice companywide for nearly 20 years and has since been adopted by other companies as well. MS SDL includes security requirements and guidelines for Microsoft products, along with tools and resources for software engineers to integrate security into their processes. 

Why the SSDLC matters

For those charged with designing, developing, implementing, and maintaining software without compromising security, the SSDLC has emerged as critical to their efforts. With agile development methodologies, the modern enterprise is churning out applications faster than ever. It’s not unusual for a single company to develop and maintain hundreds of custom apps at any given time using agile DevOps processes. And while an efficient SDLC can improve your ability to produce more applications on time, on budget, and aligned with business needs, it can also introduce vulnerabilities into the corporate environment at an unprecedented rate if security isn’t integrated into the process. With data breaches costing U.S. companies an average of $9.44 million per incident in 2022 (according to IBM’s Cost of a Data Breach report), that’s a risk enterprises can’t afford to take.

Furthermore, the traditional waterfall approach to security testing, where tests are mostly or exclusively performed at the end of the SDLC just before software is released, has proved ineffective for fast-moving, iterative software development and operations approaches. Creating an SSDLC with application security best practices and tools integrated end-to-end can help address this shortcoming.

SSDLC methods and tools

The SSDLC is more a description than any specific prescription. It refers to the general process by which an organization builds and maintains secure applications. Implementing an SSDLC can include everything from writing security requirements alongside functional requirements to performing an architecture risk analysis during application design to adopting security automation tools throughout the SDLC. 

Companies can use multiple approaches to building their SSDLC. One of the most well-known is DevSecOps (sometimes called SecDevOps), which integrates security testing alongside software development and IT operations. DevSecOps often incorporates tools and processes that encourage collaboration among developers, security specialists, and operation teams to build software in ways that are more efficient, effective, and secure. Frameworks that offer guidance to companies seeking to create an SSDLC are also available. For example, the National Institute of Standards and Technology (NIST) offers the Secure Software Development Framework, a set of practices that companies can integrate into their SDLC.

No matter the approach or framework, tools that automate security testing in order to keep up with the pace of rapid software development are essential. Among these, dynamic application security testing (DAST) stands out as the most versatile, allowing organizations to identify and test their realistic attack surface. The most advanced DAST solutions can automate security testing at multiple points in the SDLC, integrate with existing development workflows, and work alongside other tools like SAST and IAST for a layered approach.

DAST tools analyze running web applications and application programming interfaces (APIs) from the outside in, safely simulate external attacks on systems, and then observe the responses. An advanced DAST tool can help identify vulnerabilities during testing or implementation, from early builds to the final production environment. IAST tools, meanwhile, monitor running code to detect security vulnerabilities in real time and identify and isolate the root causes of vulnerabilities at the code level (including issues arising from external API interactions). 

The bottom line

Cybersecurity experts agree that any organization doing modern web application development should have an SSDLC in place. The risks of cranking out internet-facing applications without building security into the process are just too great. An SSDLC that incorporates automated security testing tools like DAST and IAST not only yields more secure software and fewer vulnerabilities but also reduces costs and increases efficiency by catching issues much earlier in the process. This greatly mitigates security and business risks, enabling organizations to implement security at the speed of software.