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SAST vs. DAST: What’s the best method for application security testing?

The differences between SAST and DAST include where they run in the development cycle and what kinds of vulnerabilities they find. Learn why you need both.

SAST vs. DAST: What’s the difference?

Recent high-profile data breaches have made organizations more concerned about the financial and business consequences of having their data stolen. They know they need to identify vulnerabilities in their applications and mitigate the risks. So they’re adding application security testing, including SAST and DAST, to their software development workflows.

What are SAST and DAST?

SAST and DAST are application security testing methodologies used to find security vulnerabilities that can make an application susceptible to attack. Static application security testing (SAST) is a white box method of testing. It examines the code to find software flaws and weaknesses such as SQL injection and others listed in the OWASP Top 10. Dynamic application security testing (DAST) is a black box testing method that examines an application as it’s running to find vulnerabilities that an attacker could exploit.

What’s the difference between SAST and DAST?

Many organizations wonder about the pros and cons of choosing SAST vs. DAST. But SAST and DAST are different testing approaches with different benefits. They find different types of vulnerabilities, and they’re most effective in different phases of the software development life cycle. SAST should be performed early and often against all files containing source code. DAST should be performed on a running application in an environment similar to production. So the best approach is to include both SAST and DAST in your application security testing program.

See a comprehensive list of the differences between SAST and DAST below:

SAST vs. DAST: What’s the difference?

SAST vs. DAST

Static application security testing (SAST) and dynamic application security testing (DAST) are both methods of testing for security vulnerabilities, but they’re used very differently. Here are some key differences between SAST and DAST:

SAST

DAST

White box security testing

The tester has access to the underlying framework, design, and implementation. The application is tested from the inside out. This type of testing represents the developer approach.

Black box security testing

The tester has no knowledge of the technologies or frameworks that the application is built on. The application is tested from the outside in. This type of testing represents the hacker approach.

Requires source code

SAST doesn’t require a deployed application. It analyzes the sources code or binary without executing the application.

Requires a running application

DAST doesn’t require source code or binaries. It analyzes by executing the application.

Finds vulnerabilities earlier in the SDLC

The scan can be executed as soon as code is deemed feature-complete.

Finds vulnerabilities toward the end of the SDLC

Vulnerabilities can be discovered after the development cycle is complete.

Less expensive to fix vulnerabilities

Since vulnerabilities are found earlier in the SDLC, it’s easier and faster to remediate them. Findings can often be fixed before the code enters the QA cycle.

More expensive to fix vulnerabilities

Since vulnerabilities are found toward the end of the SDLC, remediation often gets pushed into the next cycle. Critical vulnerabilities may be fixed as an emergency release.

Can’t discover run-time and environment-related issues

Since the tool scans static code, it can’t discover run-time vulnerabilities.

Can discover run-time and environment-related issues

Since the tool uses dynamic analysis on an application, it is able to find run-time vulnerabilities.

Typically supports all kinds of software

Examples include web applications, web services, and thick clients.

Typically scans only apps like web applications and web services

DAST is not useful for other types of software.

SAST and DAST techniques complement each other. Both need to be carried out for comprehensive testing.

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