SAST, DAST, IAST, RASP: Pros & cons

Security testing tools are essential for helping to secure your applications at every stage of the software development lifecycle (SDLC). But each comes with its own advantages and disadvantages. In this post, we’ll cover the most popular software security tools—SAST, DAST, IAST, and RASP—and how their testing mechanisms reduce security risks.

What is SAST?

Static application security testing (SAST), also known as white-box testing, allows testers to test an application’s working or internal structure. This testing methodology analyzes source code to detect security vulnerabilities and ensure compliance to coding standards, without executing the underlying code. SAST operates at the early stage of the SDLC, before application deployment.

Popular SAST tools include Checkmarx CxSAST, Fortify SAST, GitHub Code Scanning, ShiftLeft, SonarQube, Veracode SAST and WhiteHat

Pros

• Quick resolution of complex vulnerabilities, since they are detected at the early stage of the development lifecycle.
• Analyzes the entire codebase faster than manual review.
• Points out the exact location of the detected vulnerabilities in the code.
• Provides graphical representations of the issues discovered, in real time.
• Supports various programming languages.
• Easy to integrate with development and CI/CD tools.

Cons

• Cannot discover vulnerabilities in runtime, rather only when the application is compiled. This may provide a false sense of security.
• Difficult to scale and maintain applications compiled in unsupported languages.
• Requires access to source code for semantic understanding of the code.
• False positives are common, as SAST needs to synthesize data to test the code.

What is DAST?

Dynamic application security testing (DAST) is a black-box testing methodology that tests an application during its execution, indicating security vulnerabilities at runtime. DAST tools are used during the application’s testing and QA phase.

Popular DAST tools include Acunetix 360, BITSIGHT, BurpSuite, CyCognito, Detectify, Fortify DAST, Lacework, Netsparker, Qualys, Rapid7 IntsightAppSec, Security ScoreCard, and WhiteHat.

Pros

• Doesn’t require access to the source code.
• Independent of the programming language used to implement the application.
• Reduced false positives due to its ability to observe how the application responds during an attack.
• Simulates real-world attacks, alerting if the attack is successful.

Cons

• Usually applied on completed versions of the application, when it is generally more expensive to fix things.
• Doesn’t provide insights or identify vulnerabilities in the application code—only pinpoints issues that may arise as a result of a vulnerability.
• Relatively time consuming.
• Cannot pinpoint the exact location of the potential vulnerability since the exploits are executed by a third-party with no internal knowledge of the application.

What is IAST?

Interactive application security testing (IAST) combines the central ideas and approaches of both SAST and DAST. IAST places an agent inside the application, analyzing it in real time, throughout various development and deployment stages. 

Since IAST works internally, the tool has access to virtually everything in the application, including source code, libraries, frameworks, data flow, and configuration files. This yields more accurate reporting and allows security teams to check for a much broader range of threats than would be possible with SAST or DAST tools.

Popular IAST tools include Veracode, Acunetix and Checkmarx.

Pros

• Seamless integration with continuous integration (CI) and continuous development (CD) tools.
• Identifies potential issues earlier in the SDLC, making it more cost effective.
• Thorough and detailed analysis, pinpointing specific lines of code where a vulnerability or threat may be present. This makes it easy to take immediate action.
• Allows API testing, making it a great fit for microservices.
• Identifies licensing issues as well as security risks in libraries, OSS, and third-party software.
• Generally compatible with previously executed integration and functionality tests, promoting reuse of those tests for security as well.

Cons

• The agents placed internally may slow down application operations, potentially impacting performance.
• Limited language support.
• Most IAST tools are proprietary, leading to dependency on suppliers for support.

What is RASP?

Similar to IAST, runtime application security protection (RASP) runs from inside the application. Primarily used after product release, it could be considered more of a security tool than testing tool. RASP sits within the application server and has access to its runtime environment as well as inward and outward traffic. It can also control application execution. RASP continuously analyzes application traffic and end-user behavior, securing the application when it detects an attack by blocking the user’s access and alerting security teams.

Pros

• Complements SAST and DAST by providing an extra layer of protection after the application’s release.
• Can be configured to alert, log, and block activities it identifies as threats.
• Supports multiple languages and platforms.
• Integrated with the application and does not rely on network-level protections.
• Provides detailed reports and logs for analysis.
• Covers a wide range of known vulnerabilities.

Cons

• Can harm application performance, because it is deployed on the application server only.
• Can create a notion of fake security, as the tool may handle the security attack itself, but it still means that there are security vulnerabilities in the application. This can also lead to less rigorous security testing.
• Generally used only after the application has been released.
• Can’t be used as a security testing tool.

Which security testing tool is right for you?

SAST, DAST, IAST and RASP complement each other. These security tools reduce potential vulnerabilities and security threats in production while also injecting security into the SDLC at the pace modern software development demands.

Using a combination of all four of these security testing tools is ideal and is one of the easiest and most convenient approaches to mitigate security risks and secure your applications. But not every organization will have the budget to use all four.

It is important to find a balance in terms of budget and the level of security your organization needs, though it is generally recommended to use at least two of these tools for better security coverage and to lower the risk of vulnerabilities in your application. Ultimately, which tools you choose will depend on your software type, the level of maturity you need in your SDLC, and the organization’s budget and resources.

By automating security testing, you’ll be able to identify vulnerabilities and security threats in your code automatically and plan actions to remediate them. Nonetheless, many organizations lack comprehensive and rigorous testing automation, putting their applications at increased risk of being exploited by attackers.

Conclusion

There is clearly an increasing need for automation of security processes in an agile environment. And while software security isn’t cheap, the growing number of attacks means this has become a critical component. Moreover, introducing it into the SDLC as early as possible will surely improve your software security. While you may not need or be able to use all of the tools discussed here, choosing those with the greatest efficiency, speed, accuracy, and cost-effectiveness will go a long way in protecting your assets. 

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