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Out-of-band Application Security Testing (OAST) | Complete Guide

Navdeep Singh Gill | 16 Jun 2023

Out-of-band Application Security Testing (OAST)

What is OAST?

OAST stands for Out-of-band Application Security Testing; OAST is a way of observing the security of an application by testing it from an outside perspective. This method differs from conventional in-band trying out, which evaluates the software in the same environment. OAST is becoming an increasing number of users as companies search for approaches to ensure safety, other applications, and facts, in addition to meeting compliance necessities.

One of the significant blessings of OAST is that it permits companies to test their applications. In more excellent practical surroundings. They are utilizing simulating an attack from an external attitude. Agencies can better understand how their programs would carry out in the event of an actual-world attack. This can help corporations discover vulnerabilities and weaknesses that may not be detected using in-band testing methods.

Automation testing is responsible for completing repetitive tasks with better accuracy and less time span. Taken From Article, Software Testing Automation Tools

This class of OAST vulnerabilities is relatively high. It means too much to a company's security, as threat actors can use them to their advantage, and they are primarily found in REST APIs and Web applications.

Some of the out-of-band application testing bugs are as follows:

  • Blind server-side XML/SOAP injection
  • Blind XSS (delayed XSS)
  • Out-of-band SQL Injection (OOB SQLi)
  • Server-side request forgery (SSRF)
  • Host header attack
  • Out-of-band SQL Injection (OOB SQLi)
  • Email header injection
  • OS Code injection: OOB
  • Server-side request forgery (SSRF)
  • XML External Entity injection (XXE)
  • OS Code injection: OOB

Also, on the offensive side, Two HTTP/HTTPS and DNS can handle most requests, but there are some cases where various protocols, such as LDAP and SMTP, are supported to provide testers with better information. Below are the most commonly used protocols by OAST services.

  • DNS
  • LDAP
  • SMTP
  • NTLM
  • FTP
  • SMB

Comparing OAST with DAST AND SAST

A web application can have an unknown number of safety shortcomings. A large portion of these bugs are broadly known. However, areas for improvement are found routinely in old and new virtual products. Realizing this is how web applications and the dialects they are coded in will more often than not be under the relentless turn of events. They can't remain something similar for quite a while.

The powerful idea of this present circumstance makes impacts harder. It implies that no measure of testing and no mix of procedures - is ever prone to track down each possible bug in an application. To be sure, assuming it did, the circumstance would only keep going for a short time.

2 other commonly known security testing methods use in-band testing:

Invisible Vulnerabilities (DAST)

DAST stands for Dynamic application security testing. This technique will produce results with high accuracy(some may be false positives). Suppose you see the report created using this technique. In that case, you can be sure that you're looking at actual vulnerabilities, and this information can go directly to your security team to be resolved.

But when used in a sandboxed environment, dynamic testing will make detecting some vulnerabilities hard. Blind bugs are mainly missed. That's where the dynamic testing with OAST comes into play.

False Positives (SAST)

SAST stands for Static application security testing, another common security testing technique. It takes the opposite approach to DAST. When DAST considers an application from an attacker's point of view from the outside. Therefore SAST looks at the code itself. That approach gives SAST different types of drawbacks and benefits.

The main problem here is that because SAST doesn't interact with the application, it will only see what is going on in the application. This means SAST will produce a more extensive set of results than DAST, and these results come in the form of false positives. Among these will be real vulnerabilities or not, but it costs time and money for the tester to determine whether they are accurately efficient or not.

The quality assurance and software testing process of software development is as necessary as the actual code had written. Taken From Article, Software Testing Best Practices

How does Out-of-band Application Security Testing work?

In Out-of-band application security testing, the testers act as attackers, assuming the behavior and techniques of a real-world attacker to find vulnerabilities and weaknesses in the target application. This includes identifying and exploiting security flaws, such as buffer overflows, cross-site scripting (XSS), cross-site request forgery (CSRF), SQL injection, etc.

The objective of OAST is to identify security risks in the target application and determine the level of risk that the application poses to the organization. The results of OAST are then used to improve the application's security by fixing vulnerabilities and weaknesses and improving the organization's overall security posture.

OAST can be performed manually or using automated tools like Burp Suite, OWASP ZAP, and Nessus. These tools provide a variety of features to perform automated and manual testing and reporting to ensure the application is secure.

Conventional dynamic testing is elegant in its simplicity. In essence, it sends payloads to a target application and analyzes the responses that come back - just like an actual attacker might:

DAST Security Testing

When you send a DAST payload and your target comes back to you with a response containing a vulnerability, you can be sure it's real. Dynamic testing interactive features have achieved the highest because it works well in these conditions.
But when a target app doesn't send back a response to a payload, and even though the target is vulnerable to some known bug, these issues have been DAST’s weakness. Classic DAST techniques alone can't see these bugs.

Best Tools for Out-of-band Application Security Testing (OAST)?

There are several tools available for Out-of-band Application Security Testing (OAST); some of the popular ones include:

  • Burp Suite: A comprehensive software platform for web security testing. Specially Burp Collaborator, which is for OAST-type testing. Burp Collaborator runs as a single server that provides many custom implementations of network services like domain names, DNS service, Http/s service, SMTP, and many more.
  • OWASP ZAP: Web application proxy and security scanner. In OWASP ZAP, they released a Plugin, especially for OAST, that will embed with different communication services like TukTuk, BOAST, interacts, and many more.
  • Acunetix: It's a web application security testing platform that provides both automated and manual testing capabilities. Appscan provides AcuMoniter service to detect out-of-band vulnerabilities.
  • AppScan: An application security testing tool from IBM that provides dynamic and static analysis.
  • Nessus: A comprehensive vulnerability scanning and analysis tool.
    These are just a few tools; many others are available for OAST. It's essential to choose a tool that meets your organization's specific needs and ensure it is regularly updated to detect the latest vulnerabilities.
A process that applies stringent quality control measures at every stage of product development. Quality Engineering Tools and its Benefits


In conclusion, OAST is a valuable technique for testing the security of an application. It allows for a more realistic simulation of an attack and provides more thorough testing of the application’s security controls. Additionally, it can identify vulnerabilities that may not be found through traditional in-band testing methods. Many tools are available for OAST including Burp Suite, OWASP ZAPand many more. These tools provide a variety of features to perform automated and manual testing and reporting to ensure your application is secure.