What is Dynamic Application Security Testing (DAST)?

Dynamic application security testing, or DAST, is an advanced testing method for an application in an operating state. The process focuses on testing the production environment and analyzing application security at runtime. It tests how systems and components interact in practice and identifies real-world vulnerabilities without much need for insight into the provenance of any single component.

DAST testing is operational and behavioral in that testers identify problems that occur during use and then trace them back to their origins in the software design, rather than detecting issues linked to a code module. It’s useful for basic security on evolving projects and for achieving industry-standard compliance.

Advantages of Dynamic Application Security Testing

DAST benefits application security as a whole in many ways. One of the primary benefits is that a DAST security tester attempts to hack an application when it is running as an attacker would. Some additional benefits include:

Technology Independent

Because it doesn’t rely upon source code, DAST is language and platform agnostic. Not being limited by particular technologies and languages allows users to run a single DAST tool on all applications.

Fewer False Positives

According to OWASP’s Benchmark Project, there is a lower false positive rate from DAST and less noise than with other application security testing tools.

Identifies More Configuration Issues

Because DAST focuses on detecting operational security vulnerabilities and attacks applications from the outside in, it is well-suited to identify configuration mistakes other AST tools miss.

Limitations of DAST

Though there are a myriad of benefits for using DAST, there are also a number of limitations that would encourage developers to seek other means of testing.

Lack of Scalability

DAST relies heavily on effective tests, and security experts are needed to write them. This makes scaling DAST very difficult as there are often a limited number of expert resources available.

Minimal Visibility

DAST lacks visibility into the application’s code base, so DAST alone can’t offer comprehensive security coverage or insight into problematic code for purposes of remediation.

Time Consuming

DAST can be slow; according to Forrester, DAST scans can last as long as 5-7 days. DAST scans often do not detect vulnerabilities until they are more costly and time consuming to fix, later in the software development life cycle (SDLC).

How does DAST work?

Although many see dynamic application security testing as an always-automated approach, DAST is widely divided into two types: manual DAST and automated DAST.

Manual DAST simply refers to using knowledge of a specific field and experience to detect vulnerabilities DAST scanners might miss. Automated dynamic application security testing includes feeding data to dynamic application security testing protection software to test applications. This type of automated test includes scanners, fuzzers, crawlers, and other tools that can identify vulnerabilities such as cross-site scripting, SQL injection, and server side request forgery. For example, a DAST attack can send a large string of numbers to help identify a SQL injection flaw.

The best dynamic application security testing software and other DAST tools simulate various types of attacks to detect security vulnerabilities and test a broad spectrum of endpoints including hidden values. By simulating malicious attacks on an application, automated DAST security tools can help identify outcomes that are far outside typical user experience.

Dynamic application security testing products function without getting into the source code, so they demand no prior knowledge of programming language. This makes dynamic application security testing software easy to use. And because DAST detects vulnerabilities in the source code at runtime, there is no need to rebuild an application to test it for vulnerabilities.

DAST vs other application security testing

In terms of SAST vs DAST vs IAST, each kind of application security tool takes a different approach to web application security. There are several categories to understand:

Static Application Security Testing (SAST)

Static application security testing is a methodology for white-box testing in which source code is analyzed from the inside outward while components are at rest.

Interactive Application Security Testing (IAST)

Interactive application security testing is a kind of hybrid, grey-box strategy that works through instrumentation of the code from within an application while it is running to detect and report issues.

Software Composition Analysis (SCA)

Software composition analysis offers visibility into open source software components by scanning the code base for application vulnerabilities including license compliance issues.

Static vs Dynamic Application Security Testing

The difference between static and dynamic application security testing is that DAST takes an “outside in” approach, attacking the application like a malicious actor would. A DAST scanner performs these attacks, and identifies security vulnerabilities from results that are unexpected within the result set.

Conversely, SAST analyzes the source code of an application, a static environment, an “inside out,” approach, searching for vulnerabilities. SAST scanners must support both the language and the web application framework in use. In contrast, DAST scanners rely on HTTP and interact with an application from the outside.

It is a best practice to use both SAST and DAST to optimally strengthen security posture. To address this DAST vs SAST issue, the Interactive Application Security Testing (IAST) grey-box methodology was developed, combining the benefits of both methodologies).

Dynamic Application Security Testing vs Penetration Testing

Although they seem similar, there is a difference between dynamic application security testing and penetration testing. DAST testing systematically focuses on the running state of the application, while penetration testing (with owner permission) uses common hacking techniques to exploit vulnerabilities in the application and beyond it, including ports, firewalls, servers, and routers.

During penetration testing (or pen testing), a cyber-security expert launches simulated attacks to find computer system vulnerabilities and identify weak spots attackers could exploit. Modern pentesting blends technology and automation with the human expertise of manual testers.