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In this age of heightened cybercriminal activity, all online enterprises need to know how to defend against application layer attacks. Since proactive defense is always better than reactively scrambling to rebuild defenses after a successful intrusion, most successful enterprises rely on DAST tools to bolster their application security and identify possible threats before they are realized. Let’s break down what DAST tools are and how they might help your enterprise in the future.

What is DAST?

“DAST” is an acronym for Dynamic Application Security Testing. Put another way, DAST is a category of web scanning tools that can help find various security vulnerabilities in certain web applications. Rather than looking for issues from the inside, DAST tools conduct a scan of vulnerabilities from the exterior of a web application without accessing source code architecture.

For this reason, DAST is commonly classified as a “black box” security solution.

DAST scanners work utilizing two key parts: a “crawler” element that can explore a web application and discover all the URLs possible and a “detection” element that can execute various requests against URLs individually. In this way, DAST scanners both find and “attack” URLs in a web application to test them for various vulnerabilities.

To use a DAST tool, a network administrator or operator directs the scanner to target a home URL. The crawler element starts to navigate through different URL links through the primary URL. This does limit DAST tools to URLs that are accessible from the home page. However, most DAST scanners also have options to let you enter additional URLs manually.

After building a list of suitable URLs, a DAST scanner will run through a list of various request formats, usually involving payload attacks to test a network for certain types of security issues. The list of request formats can be personalized based on the technologies of the system in question or based on likely cyberattacks.

Depending on the sophistication of the DAST tool and the number of URLs to test, this process can take up to several days.

However, once completed, a DAST scan can provide lots of actionable information for a network administrator or IT security team. Specifically, feedback can include:

  • The types of security vulnerabilities encountered/detected
  • Which URLs were affected by the security vulnerabilities
  • Any additional parameters that might have affected the request

Again, DAST tools utilize external scans, so no details regarding how the issue cropped up from the source code of the application will be provided. 

DAST tools are, therefore, best at testing the HTML and HTTP interfaces of web applications to simulate the kinds of attacks a cybercriminal would use to get into a service or application. It’s a proactive type of security testing that can help catch issues where trawling through hundreds of lines of code would be impractical or less than helpful.

Benefits of DAST

DAST tools aren’t perfect and everything, but they do provide several benefits that might make them a good choice for your web application over SAST or other tools.

Totally Application Independent

Because DAST tools don’t delve into an app’s source code, they can be used regardless of the platform or language you’re working with. As a result, a single DAST tool can run on all your applications, and can even be utilized for applications that are different from one another but may nonetheless interface frequently. Thus, DAST tools are often cost-effective or excellent for enacting widespread security scans in a reasonable timeframe.

No Configuration issues

When your application is fully operational, DAST does a great job of finding security vulnerabilities. Since it looks at your application from an outside perspective, a DAST scanner is perfectly positioned to discover configuration mistakes that might be missed from other types of security scanning tools. For instance, configuration issues that might not be obvious from a code-based perspective will be easily identifiable with a DAST scanner.

Not Many False Positives

The OWASP Benchmark Project, a Java-based test suite that was designed to evaluate how well different software vulnerability detection tools performed found that DAST tools had a lower than average number of false positives. As a result, DAST scanners are reliable and should serve as cornerstone or staple scanners for your IT security teams. 

Good Penetration Testing Utility

By manually testing for penetration with a DAST scanner, you can automate various penetration tasks to directly see how your system responds to such intrusions and whether or not it catches different attack payloads. However, keep in mind that this benefit is strongly correlated with the skill of the operator, so more knowledgeable security experts or application administrators will make the most of this benefit.

Disadvantages of DAST

Although it’s definitely wise to consider DAST security tools for your applications, there are some disadvantages you should be aware of so you aren’t caught off guard.

Vulnerability Reporting is General, Not Specific

Since DAST doesn’t take a look at your application’s source code architecture, it can’t tell you exactly why the security vulnerability exists. Any DAST scanner report will include the type of vulnerability, which URLs were affected, and certain parameters about the request.

It's up to your IT team or another scanner to identify what issue in the code is what issues with compatibility might exist to cause the security vulnerability in the first place. You may still need to spend a lot of time fixing a security problem after identifying it. 

Put another way, you’ll need extensive IT security expertise to successfully parse a DAST scanner report and determine what’s wrong.

Complex Risks May Go Unnoticed

The same OWASP Benchmark test mentioned above found that, while DAST had a low number of false positives, even extremely sophisticated or effective scanners can only find about 18% of existing security vulnerabilities. That’s because more complex vulnerabilities usually go unnoticed by DAST tools. As a result, DAST tech is more effective for finding simple or overlooked security issues as opposed to determining deep errors or flaws that might be exploited one day.

Furthermore, certain security risks for your web applications can’t be identified from the exterior: common examples include blind SQL injection and insecure deserialization.

Time Consuming

DAST scanners can, as mentioned, take up to several days to complete, especially with more complex web applications. If your team needs to push out new code pretty frequently, DAST scanners may not be effective.

This is true both for the initial scan and for any follow-up scans you might need to perform after identifying and attempting to fix a reported security vulnerability. Since you have to make a new DAST scan after each fix attempt, the time required to utilize DAST tech for your application’s security can quickly pile up.

Late Application in the Software Development Process Lifecycle

Because DAST tools have to look at the outside of a web application and are most effective when used on operational applications, they’re typically deployed toward the end of an app’s development lifecycle. As a result, any issues detected may require an application team to go back and undo weeks of work. It’s always better to catch issues earlier in the development lifecycle to prevent wasted time and effort.

Differences Between DAST and SAST

DAST tools are only one type you can use to test a web application for vulnerabilities. Another popular alternative is Static Application Security Testing, or SAST, technology. As "white box" testing tools, SASTs scanners can look through the source code architecture of applications so long as they are at rest rather than currently operate.

In a way, SAST tools are the opposite of DAST scanners – they look at an application from the inside out instead of from the outside in. They also have many of the opposite benefits and drawbacks.

For example, SAST tools are best used early in a software development lifecycle to find and fix vulnerabilities before development continues. SAST scanners can also directly identify any defective code segments, pointing out exactly what needs to be fixed and where.

Basically, SAST tools have the edge over DAST tools since they show developers and programmers what the problem in their source code is and how to fix it, saving time and money.

But SAST tools are also a little more limited in exchange for this functionality. SAST tools must support the programming language of the application in question, meaning they aren’t as versatile compared to even a basic DAST tool. Furthermore, DAST scanners put you in the perspective of an attacker, which can be valuable for skilled security specialists who know that most attackers won’t have access to an application’s source code anyway.

The bottom line? It’s almost always best to use both DAST and SAST scanners and tools together to cover all your bases. SAST tools should be implemented early, even if you just have one scanner tailored for your application’s programming language or architecture. After your software has reached a later stage of the development cycle, DAST scanners should be brought into play to check for any vulnerabilities you might have missed.

How to Implement DAST?

First, you’ll need to identify different which applications you want to test – remember, DAST scanners are used with applications that are already operational (at least to a large extent). Furthermore, you’ll need someone skilled with IT security and threat identification to successfully interpret DAST scanner results. Find this person early and before you launch your DAST tools.

Then you need to define and utilize a “triaging workflow”. This will allow you to prioritize different vulnerability scan results and investigations. DAST tools have a low rate for false positives, though they are still possible.

Lastly, remember that a DAST scan must be repeated after you attempt to fix any detected security vulnerabilities. Budget time and manpower for this to ensure that you actually solved any detected security problem rather than worked around it.

Top DAST Tools

There are several fantastic DAST tools available, especially since they are simplistic and versatile compared to their SAST counterparts. Here are just a few excellent examples.

Appknox

This dynamic DAST security solution works to identify vulnerabilities in applications already up and running. It can flag all types of common security vulnerabilities, such as Man in the Middle attacks. Installing the tool is quite easy, as you only have to upload the application binary code to an Appknox cloud-hosted device.

Even inexperienced techs should be able to use the platform with these. A simplistic and intuitive dashboard, plus related controls, makes launching a scan and generating reports quick and simple.

Three versions of Appknox are available, ranging from Essential to Professional to Enterprise. Each level is suitable for different businesses or enterprises.

Netsparker

This popular DAST scanner is one of the most in-depth tools available, offering fantastic vulnerability scan functions for any type of web application. It’s also one of the best DAST tools since it offers an extremely low false-positive rate. Vulnerabilities it can detect include remote file inclusion, local file inclusion, un-validated redirect, SQL injection, and more. 

It’s also a great choice if you don’t relish the idea of your DAST taking too long, as Netsparker can scan thousands of application URLs in just hours. It can verify most of its vulnerabilities automatically without your team having to sift through the reports one by one.

Veracode Dynamic Analysis

This last DAST tool is a dream to work with, in large part because it lets you schedule automated scans. This allows you to scan web applications consistently and without having to assign someone to manually do so every few hours or days.

It’s a versatile and effective tool and even allows you to scan web applications that are behind login screens, both manually and automatically. False-positive rates are lower than 1% on average, and it’s ultimately easy to use from a centralized dashboard. Whether you want to scan a single URL or a collection, Veracode gets the job done.

Conclusion

Ultimately, DAST tools are just one part of an excellent security toolkit and a cornerstone scanner type that all application security teams should know how to use. For the best results, combine DAST scanners with SAST scanners and use both types of tools correctly. If done right, your application will be much safer from an enterprising cybercriminal.