SCA (Software Composition Analysis) and SAST (Static Application Security Testing) tools both play important roles in secure application development, but there are notable differences between them.
The biggest is that SCA tools focus on open source dependencies and their associated risks, while SAST tools focus on your proprietary code — e.g., the custom code your developers write or maintain, including how an open source component is used in proprietary code.
As such, SAST provides a different perspective on vulnerabilities or weaknesses than SCA. Where SAST would tell you, “Your code has improper input validation,” SCA would tell you, “The code (OSS) your code is using has improper input validation.” In other words: The tools surface similar vulnerabilities, yet on dramatically different attack surfaces.
Another significant difference is SCA has multiple use cases beyond vulnerability management, including SBOM management and open source license compliance.
For these reasons, SCA and SAST are considered complementary: SAST tests your code and coding practices, while SCA tests your third-party code.
In this blog, we’ll explain how both SCA and SAST work, the important differences between them, and how the tools can work together to strengthen security.
SCA tools analyze, inventory, and manage open source dependencies, their licenses, and their vulnerabilities. SCA works by scanning software applications to identify the third-party components and libraries they depend on. SCA tools can integrate with various development and CI/CD tools to automate the analysis as part of the software development process.
SCA supports several distinct use cases:
Open source license compliance: SCA tools report a list of open source licenses (and their associated dependencies) when scanning code. Some SCA tools (like FOSSA) will also list the obligations that your licenses carry — and even offer functionality to help achieve compliance, such as automating license notice creation. Additionally, SCA tools with strong policy engines can be configured to block builds if an out-of-policy license is detected.
SBOM generation: Creating a software component inventory is a fundamental SCA capability, so it shouldn’t be a surprise that many SCA tools also support SBOM generation. For example, organizations can use FOSSA’s SCA offering to generate SBOMs in both the SPDX and CycloneDX formats, with a range of customization options. Some SCA tools also support third-party SBOM ingestion and management.
Open source vulnerability management: Beyond providing an inventory of known vulnerabilities (CVEs), SCA can help with prioritization and remediation. For example, FOSSA will show the CVSS and EPSS scores for a given vulnerability to support prioritization, and we’ll also report the fix and code path to help with remediation.
SAST is used to analyze an application’s source code, bytecode, or binary code for security vulnerabilities — without executing the program. SAST tends to be used very early in the software development lifecycle (such as in the development phase), which helps developers and security teams address possible security issues before deploying an application.
SAST identifies potential vulnerabilities by using predefined rulesets or security patterns. These rulesets are created based on known security best practices and common coding mistakes that may lead to security issues, including SQL injection, cross-site scripting (XSS), buffer overflows, and other security vulnerabilities. In practice, these vulnerabilities result in threat actors escalating authorized privileges, accessing restricted data, or executing malicious code.
SAST utilizes several techniques to identify vulnerabilities, such as:
As we’ve discussed, although SCA and SAST both support security use cases, there are significant differences between the two tools. Here are some of the biggest.
Despite these differences, it is worth noting that a majority of vulnerabilities reported by SCA tools are the direct result of "SAST" scans on the source of an open source dependency. So, essentially, most open source vulnerabilities are SAST results run against that proprietary or open source code that have been published in a public database (such as MITRE, NIST, GitHub advisory, and so forth).
Although SAST and SCA work differently and have different purposes, they’re both important parts of managing security risks for modern applications. As such, many organizations benefit from using both tools. This is often done via integration into your CI/CD pipeline, which ensures that security assessments are conducted automatically with every code commit and deployment, providing timely feedback to developers.
With SCA and SAST in place — along with other testing tools and the right people and processes — organizations can strengthen their defenses against a range of security and open source license compliance risks.
For more information on FOSSA’s SCA tool and how it works, we recommend visiting our SCA product page.
Here at GitHub, we work hard to give you the right tools and knowledge so you can keep your projects secure. From providing best practices on keeping your projects safe to explaining today’s most common security vulnerabilities, it’s our job to help make the open source ecosystem a safe and productive place.
And the security space has changed. I remember when I first started my security career, it was common for organizations to have security experts test code right before it was about to ship. But these days, several application security testing tools have gained popularity—allowing developers to secure their code themselves. These include static application security testing (SAST), dynamic application security testing (DAST), software composition analysis (SCA), and interactive application security testing (IAST) among others. Such tools empower individual developers to become security experts—bypassing the frustration and wasted time and money that come with reactive security approaches.
Today, we’ll focus on SCA and SAST. Both these capabilities strengthen security and empower you to stay ahead of attackers. But what exactly are they? And which one is right for your project?
SCA tools help you detect and manage the security posture of all open source components in your organization’s codebase. Once a piece of open source code is identified, these tools can determine whether there are any security threats or licensing information that requires attribution or policy compliance. Advanced SCA tools automate the entire process of managing open source components. They also provide comprehensive information about the vulnerabilities so developers can easily fix them. SCA tools can be used throughout the software development lifecycle (SDLC).
SAST tools address security issues in your organization’s proprietary software. They analyze source code by scanning it for known vulnerable code patterns. This generates the identification of potential security flaws and vulnerabilities. SAST takes place early in the SDLC, as it does not require a working application and can take place without executing code. SAST tools give developers real-time feedback as they code, helping them remediate issues before the code is passed onto the next phase of the SDLC.
SCA SAST Addresses open source code Addresses proprietary code Fixes involve patching vulnerabilities Fixes involve writing more secure code or addressing security weaknesses Commonly has false negatives when a library is not known by a tool Commonly has false positives where an issue is not in fact a security riskSCA and SAST work synergistically with each other and are both important for keeping your software secure.
With SCA tools, it’s easier to fix vulnerabilities, as developers simply need to patch or download the latest version of the source code. SAST tools typically provide guidance on how to remediate, but the suggestions can be difficult to follow and require code changes. Both tools can be used across the SDLC, but the best collaboration occurs at the pull request.
With SCA tools, we can see the false negatives—that is, the library is not indexed and therefore is not matched. SCA tools are fast and run their scans in seconds with no impact on build, no matter the size of the project. However, traditional SAST tools are more time-consuming since they were built at a time when testing was done outside of the SDLC (GitHub’s code scanning, by contrast, is done inside the SDLC, taking far less time).
As you can see, SCA and SAST tools cover different areas. They are both important pieces to the puzzle of keeping your software secure.
As the home for all developers, we have our own versions of SCA and SAST: Dependabot and code scanning, respectively. Developers are welcome to use Dependabot and code scanning for free on their OSS projects. Enterprise users can leverage GitHub Advanced Security (GHAS) to secure their code
Dependabot makes it easy to find and fix vulnerable dependencies in your repository. Once enabled, it’s always on to alert you about vulnerabilities in the software you depend on. You can even go further by enabling Dependabot security updates, and Dependabot will automatically create pull requests to fix security alerts as they happen.
Dependabot catches dependencies in real time, allowing you to understand:
Code scanning examines your code for security issues as it’s being written and integrates fixes natively into your developer workflow. Every Git push is scanned for new potential vulnerabilities. Results are displayed directly in your pull request. Code scanning uses CodeQL, which includes more than 2,000 CodeQL queries written and open-sourced by the GitHub Security Lab and leading researchers. This helps you find vulnerabilities with minimal configuration.
We know there are a lot of tools out there promising the best security experience. We hope you walk away with a better understanding of how SCA and SAST tools differ and how they can help secure your code.
To learn more about Dependabot, visit our Dependabot Docs page.
To learn more about code scanning, visit our code scanning Docs page.
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