SAST vs. DAST: Understanding the Differences Between Them

The exponential rise in malicious activities and cybercrime has made companies pay more attention to application security. It has also sparked widespread discussion about the benefits and challenges of various application security testing solutions available in the market.

Web application firewalls (WAF), interactive application security testing (IAST), and penetration testing (pen testing) are widely implemented security solutions. However, they are typically used to complement the two most popular application security testing solutions - static application security testing (SAST) and dynamic application security testing (DAST).

Both SAST and DAST are application security testing solutions used to detect security vulnerabilities that can make an application susceptible to attacks. SAST and DAST are two commonly used acronyms for developers and security testers, however, there is a lot of confusion around these two terms.

Which of these application security testing solutions is better?

Is SAST more effective than DAST at identifying today’s critical security vulnerabilities or is DAST better?

SAST vs. DAST: Which method is suitable for your organization?

Before diving into the differences between SAST and DAST, let’s take a closer look at what exactly SAST and DAST actually are.

What is Static Application Security Testing (SAST)?

Static application security testing (SAST) is a white box security testing method where the tester has access to the underlying source code. In SAST, the application is tested inside out.

Why should you perform static application security testing?

Companies build feature-rich, complex applications to engage customers and other stakeholders in multiple ways. If security vulnerabilities are not eliminated from these applications, they may expose customers’ sensitive information to attackers, which could lead to severe damage or cripple the business.

For instance, a distributed denial of service (DDoS) attack is one of the most infamous types of attacks that target online services and web applications. It aims to overwhelm the application with more traffic than the network or server can accommodate which often renders the site inoperable.

According to a report, the average cost of a DoS or DDoS attack could cost more than $120,000 for a small organization and $2 million for larger organizations.

Considering most cyberattacks related to software vulnerabilities occur within the application layer, it is critical to implement robust security testing methods such as SAST.

Testers can conduct SAST without the application being deployed, i.e. it analyzes the source code, binaries, or byte code without executing the application.

SAST can be conducted early in the software development lifecycle (SDLC) which means potential security vulnerabilities are found earlier in the SDLC, so it becomes easier to identify and mitigate them.

However, since SAST tools scan static code, it cannot find run-time vulnerabilities.

What Are the Benefits of Using SAST?

Let’s take a look at some of the advantages of using static application security testing:

• SAST is a highly scalable security testing method.
• It can be automated; helps save time and money.
• It is ideal for security vulnerabilities that can be found automatically such as SQL injection flaws.
• SAST can direct security engineers to potential problem areas, e.g. if a developer uses a weak control such as blacklisting to try to prevent XSS.
• Since SAST tools determine the exact location of a vulnerability or flaw, it becomes easier for developers to locate vulnerabilities and fix them in a timely manner.

What Are the Challenges of Using SAST?

Using static application security testing does have some cons.

They include:

• SAST tools are often complex and difficult to use.
• It requires access to the application’s source code, binaries, or byte code, which some companies or teams may not be comfortable with sharing with application testers.
• SAST tools cannot determine vulnerabilities in the run-time environment or outside the application, such as defects that might be found in third-party interfaces.
• Each SAST tool typically finds different classes of potential weaknesses, which might result in a slight overlap between the results of different SAST tools.
• Many false positives to weed through, you may want to consider a service such as Cypress Defense AppSec service where we run the SAST tool, get rid of false positives, and then insert true issues into your issue tracking system.

What is Dynamic Application Security Testing (DAST)?

Dynamic application security testing (DAST) is an application security solution in which the tester has no knowledge of the source code of the application or the technologies or frameworks the application is built on.

In DAST, the application is tested by running the application and interacting with the application.

It enables the tester to detect security vulnerabilities in the application in a run-time environment i.e once the application has been deployed.

Dynamic testing helps identify potential vulnerabilities including those in third-party interfaces.

Why Should You Perform DAST?

DAST provides insights into web applications once they are deployed and running, enabling your organization to address potential security vulnerabilities before an attacker exploits them to launch a cyberattack.

As your web applications advance, DAST tools continue to scan them to quickly identify and fix vulnerabilities before they become serious issues.

For instance, a common web-based attack is cross-site scripting (XSS), in which attackers inject malicious code into the application to steal sensitive data such as session cookies, user credentials, etc.

Another popular web-based attack is an SQL Injection, in which attackers insert malicious code in order to gain access to the application’s database.

DAST tools give development and security teams visibility into potential weaknesses and application behavior that could be exploited by attackers.

DAST helps search for security vulnerabilities continuously in web applications and it is recommended to test all deployments prior to release into production. Once these weaknesses are identified, automated alerts are sent to concerning teams so that they can analyze them further and remediate the vulnerabilities.

What Are the Benefits of Using DAST?

Let’s check out the pros of using dynamic application security testing:

• DAST can determine different security vulnerabilities that are linked to the operational deployment of an application.
• Testers do not need to access the source code or binaries of the application while they are running in the production environment.
• DAST enables testers to perform the actions of an attacker which helps discover a wide variety of security vulnerabilities that may be missed by other testing techniques.
• It helps testing teams explore security vulnerabilities beyond the application including third-party interfaces and outside the source code.

What Are the Challenges of DAST?

Here are some of the cons of using dynamic application security testing:

• Delayed identification of weaknesses may often lead to critical security threats.
• DAST tools cannot mimic an attack by someone who has internal knowledge of the application.
• It cannot discover source code issues.
• It is only limited to testing web applications and services
• Many false positives to weed through, you may want to consider a service such as Cypress Defense AppSec service where we run the DAST tool, get rid of false positives, and then insert true issues into your issue tracking system.

SAST and DAST: What Are the Differences Between These Two Application Security Testing Solutions?

Many companies wonder whether SAST is better than DAST or vice versa. However, both of these are different testing approaches with different pros and cons.

Both these application security testing solutions find different types of security vulnerabilities, use different methods, and are most effective in different phases of the SDLC.

Here’s a comprehensive list of the differences between SAST and DAST:

SAST vs. DAST in CI/CD Pipelines

SAST: Static application security testing solutions can be integrated directly into the development phase, enabling developers to monitor the code regularly.

They cover all stages of the continuous integration (CI) process, from security analysis in the code of the application through automated scanning of code repositories to the testing of the built application.

This leads to quick identification and remediation of security vulnerabilities in the application.

DAST: Dynamic application security testing tools can only be used after the application has been deployed and running (though it can be run on the developer’s machine but are most often used on a test server) therefore delaying the identification of security vulnerabilities until the later stages of the development.

Vulnerability Coverage and Analysis

SAST: SAST solutions help detect both server-side and client-side vulnerabilities with high accuracy. SAST solutions are highly compatible with a wide range of code, including web/mobile application code, embedded systems, etc.

DAST: Black box testing helps analyze only the requests and responses in applications. This means that hidden security vulnerabilities such as design issues can go undetected when using Dynamic application security testing solutions.

Mitigate/Remediation Performance

SAST: With SAST solutions, code can be scanned continuously (though scan times can be lengthy) and security vulnerabilities can be identified and located accurately, which helps development and security testing teams to quickly detect and remediate vulnerabilities.

DAST: While DAST tools help identify security vulnerabilities in an application when it is running in a testing environment, it does not provide the exact location of those vulnerabilities.

Thus, developers and security teams have to waste time locating the points in the source code to correct the vulnerabilities detected by DAST. This can be a time-consuming process that can be even more complicated if a new member who is not familiar with the code has to fix it.

Cost Efficiency

SAST: White box security testing can identify security issues before the application code is even ready to deploy. While this is very helpful, SAST does need to know the programming languages and many newer frameworks and languages are not fully supported.

This makes SAST a capable security solution that helps reduce costs and mitigation times significantly.

DAST: DAST is implemented after the code has been compiled and the application is in a run-time environment, so it may not discover vulnerabilities until later stages of the SDLC.

Missing these security vulnerabilities along with a delayed identification of existing vulnerabilities can lead to a cumbersome process of fixing errors. This also leads to a delayed remediation process.

Takeaways

Both types of application security testing solutions come with their own set of benefits and challenges, however, they can complement each other.

SAST can be used early in the SDLC process and DAST can be used once the application is ready to be run in a testing environment. Comprehensive testing can be done using both SAST and DAST tools to detect potential security vulnerabilities.

Which application security testing solution should you use?

The ideal approach is to use both types of application security testing solutions to ensure your application is secure.

While it may seem overwhelming at first, it’s well worth the time and effort to protect your application from cyberattacks so that you don’t have to deal with the aftermath of a breach.

If you’re wondering where to get started or want to conduct a security audit to ensure your SAST and DAST tools are in place, reach out to us. We’ll be happy to help you ensure your applications are secure.