Security Audit

Black-Box Penetration Testing: A Complete Guide

Updated on: January 24, 2023

Black-Box Penetration Testing: A Complete Guide

One way to tackle the rampant problem of insecure software is penetration testing. Penetration testing (aka Pentesting) is a way to discover & fix hidden vulnerabilities in a system. There are three approaches to penetration testing – white-box, gray-box, and black-box penetration testing. All three types are quite popular in security testing. One, but, needs to know the objectives & differences of these pentesting styles to choose the right kind. In today’s post, we are breaking down black-box penetration testing for you.

What is black-box penetration testing?

Black-box penetration testing is a penetration testing service that aims to find & exploit vulnerabilities in a system as an outsider. In black-box penetration testing, the security expert is provided with no information of the target system prior to the testing. Except for the target URL and (maybe) access similar to an end-user. This means the tester has no access to source code (other than publicly available code), internal data, structure & design of the application before the testing.

The name “black-box’ is suggestive of the dark, no-information starting point in the test.

A black-box penetration test tests your live application, on run-time. It is thus also called Dynamic Application Security Testing (DAST). A black-box pentest is great for testing your external assets like:

  • Web-apps
  • SaaS apps
  • Network
  • Firewall 
  • Routers 
  • Web servers
  • Application servers
  • Database servers, etc. 

While black-box penetration testing is not an alternative to complete security review, it helps in testing the application from the POV of an end-user or a hacker. It can flag serious vulnerabilities in your web-facing assets such as – validation errors, information disclosure via error messages, server misconfigurations, and so on.

8 Benefits of black-box penetration testing

Black-box penetration testing on its own is not sufficient for identifying all security vulnerabilities in a system. Though, when coupled with source code review and other tests, it provides a wholesome picture of the security status of the system & network.

Here’s how you can benefit from a black-box pentest:

  1. It tests your application as a hacker. In a true sense
  2. It finds the exposed vulnerabilities on your networks and apps
  3. Since it tests the application on run time, it can help you detect implementation & configuration issues
  4. It detects incorrect product builds (e.g., old or missing modules/files)
  5. It can detect security issues relating to people – by employing social engineering techniques
  6. It can detect security issues that arise as a result of interaction with the underlying environment (e.g., improper configuration files, unhardened OS, and applications)
  7. It can detect issues like input/output validation errors, information disclosure in error messages, etc
  8. It can be cheaper to conduct a black box penetration test compared to other pentesting types like – gray box & white box
Benefits & drawbacks of black-box penetration testing
Benefits & drawbacks of black-box penetration testing

Also Read: Website Penetration Testing- A Complete Guide | Continuous Penetration Testing: The Best Tool You’ll Find in 2022

3 Drawbacks of black-box penetration testing

A black-box penetration test is an important component of application security testing. However, in no circumstance, should you trade off a comprehensive review of the source code and internal system for a black-box pentest.

Since a black box test does not include internal testing, a system may falsely appear to be ‘secure’ if the tester fails to find any vulnerabilities in the external components. In reality, the application may have a pile of vulnerabilities beneath the surface.

In other words, vulnerabilities identified in a black-box test indicate that the target system has a weak security build. The same can’t be said when it does not highlight any important security vulnerabilities. In that case, the vulnerabilities are just hidden inside the internal systems.

To sum up, a black box penetration test:

  1. Doesn’t provide a complete picture of the target’s security system
  2. Is based on endless guesswork, and trial & error.
  3. Can range either way on the time scale. It can take the least amount of time to identify vulnerabilities or can take months to recon and identify a single vulnerability. It all depends on the expertise of the tester.

Also Read: API Penetration Testing: What You Need To Know

Black-box vs Gray-box vs White-box penetration testing

Clearly, black-box penetration testing isn’t enough. This is where gray-box & white-box penetration testing comes in. To better understand these three penetration testing styles, let’s look at their differences:


  • Is conducted without any prior intel of the target system.
  • Only tests the exposed environment.
  • Is not at all in-depth.
  • Consists of guesswork, and endless hit & miss sessions.
  • Automation is heavily used.
  • ETAs are unpredictable. Can be very fast or take months on end.
  • Is cheaper.

Related Blog – Template of Pentesting Report | Why Firewall Penetration Testing is Essential to Your Security Strategy


  • Is conducted with partial intel of the target system.
  • Tests exposed vulnerabilities in outer systems as well as hidden vulnerabilities in internal systems.
  • Provides a fairly better picture of the system’s security.
  • Very limited use of guesswork involved.
  • Automation is used sparsely. Only to replace repetitive and tedious scanning work.
  • Takes a predictable amount of time to complete. Time often ranges from several days to a couple of weeks.
  • Costs lie between the two extremes.


  • Is conducted with complete intel of the target system.
  • Conducts thorough testing of all assets – external, internal, and code.
  • Provides a complete picture of the system’s security.
  • No guesswork involved.
  • Automation is used only as an aid to the manual process. Only to replace repetitive and tedious scanning work.
  • Takes a couple of months to complete.
  • Is costly.
white-box vs gray-box vs black-box penetration testing
Differences between black-box, white-box, & gray-box penetration testing

Keeping in mind the limitations of a black-box penetration test, at Astra, we offer both black-box & gray-box penetration testing. Black box testing helps with regular pentesting of your application which you can use at your own code push cycle’s pace. The gray box testing ensures that our security experts try to break into the application like a hacker and look into the internal as well as external threats.

All vulnerabilities are then reported on our Pentest dashboard, which simplifies overall vulnerability management for both the involved parties – the tester & the client. More information here.

Also Read: What is Automated Penetration Testing? Difference between Automatic & Manual Pentesting Software

It is one small security loophole v/s your entire website or web application

Get your web app audited with Astra’s Continuous Pentest Solution

6 Common black-box penetration testing techniques

Black-box penetration testing techniques
Black-box penetration testing techniques

1. Fuzzing

Fuzzing is a process to test web interfaces for missing input checks. It’s done by injecting random or well-crafted data, also called noise injection. The goal is to identify unusual program behavior that results from noise injection. The success of Fuzzing may indicate the lack of proper checks in the software.

2. Syntax testing

Syntax testing is a process to test the data input format used in a system. Usually, this is done by adding input that contains garbage, misplaced or missing elements, illegal delimiters, etc. The aim is to find out the outcomes in case the inputs deviate from the syntax.

3. Exploratory testing

Exploratory testing is testing without any pre-formed test plan or expectation of a specific outcome. The idea is to let outcomes or anomalies of one test guide another. It is especially helpful in black-box penetration testing, where a big find may shape the whole test.

4. Data analysis

Data Analysis in black-box penetration testing refers to the review of the data generated by the target application. It helps the tester understand the target’s internal functions.

5. Test scaffolding

Test Scaffolding is a technique to automate intended tests with tools. This process helps the tester find out critical program behavior otherwise not possible in manual testing. These tools usually include debugging, performance monitoring, and test management tools.

6. Monitoring program behavior

Monitoring program behavior helps the tester understand how the program responds. With this technique, the tester may find unspecified symptoms that are indicative of underlying vulnerabilities. This process can be automated to save testers from manually checking for anomalies in program behavior.

Related Blog – Penetration Testing Cost

5 Stages in a black-box pentest

A typical black-box penetration testing goes through these 5 stages:

Stages in black-box penetration testing
Stages in black-box penetration testing

1. Reconnaissance

Reconnaissance is the process of gathering preliminary information about the target system. The intel may include information like – IP addresses, email addresses, employee information, websites, exposed pain points, and so on.

2. Scanning & Enumeration

Scanning & Enumeration is where more reconnaissance is done. This is where the tester looks for more data about the target like types of running software, operating system, versions, connected systems, user accounts, user roles, etc.

3. Vulnerability Discovery

With the above reconnaissance, the tester now looks for public vulnerabilities in the target systems & networks. This may include known CVEs in the system, versions, or third-party applications used by the target.

4. Exploitation

Exploitation is where the tester crafts a malicious request, or social engineer to exploit the identified vulnerabilities. The goal of this step is to get to the heart of the system via the shortest route possible. 

5. Privilege Escalation

After the tester breaks into the system, they try to escalate their access level to gain complete access to the system and database. This stage is called Privilege Escalation.

Tools used in a black-box pentest

Related Read: Top Penetration Testing Software & Tools Pros Use | Top 5 Software Security Testing Tools in 2022 [Reviewed]

Black-box penetration testing by Astra Security

Astra Security offers a black-box pentest with Astra’s automated vulnerability scanner. Our scanner scans your application & network for 2500+ exposed vulnerabilities, with new vulnerabilities added from time to time.

We also conduct static & dynamic code analysis, business logic testing, payment gateway testing as is done in a white-box pentest under our manual pentest engagement.

Here’s what else you get with Astra Pentest:

  • An intuitive vulnerability management dashboard
  • Detailed vulnerability reports (including PoCs, steps-to-reproduce, selenium scripts, etc.)
  • Monetary loss value associated with a vulnerability
  • Intelligently calculated risk score for each vulnerability
  • Hacker-style pentest with 2500+ tests
  • Ability to collaborate within our dashboard with security engineersManual scanning/pentest
  • A grading system to rank the security of your assests
  • Detailed steps-to-fix and fixing advice from security engineers
  • Publicly verifiable certificate

Learn more about Astra’s Pentest Suite here.

Also Read: Top 6 Web Pentest Tools You Should Not Miss in 2022

Astra’s Pentest Suite


As celebrated software engineer & author Boris Beizer said,

“Software never was perfect and won’t get perfect. But is that a license to create garbage? The missing ingredient is our reluctance to quantify quality.”

Security of software is an ongoing process. You develop, test, secure, and repeat. There are various ways to test an application. Penetration testing is one of the most common.

Black-box penetration testing helps you test your live application for implementation, validation, and other errors. On its own, black-box penetration testing does not reveal everything wrong with the application’s security. Combining a black-box penetration test with other tests, such as source code review, increases its effectiveness.


What is the timeline for Black-Box Penetration Testing?

The timeline for Black-Box Pentesting is 7-10 days. The rescan after fixing the vulnerabilities takes 3 more days. The timeline may differ slightly based on the scope of the test.

How much does penetration testing cost?

The cost for penetration testing ranges between $99 and $399 per month for websites.

Why choose Astra Pentest?

The security engineers at Astra perform extensive manual pentest on top of machine learning driven automated scans. The vulnerability reports appear on your dashboard with detailed remediation guides. You will have access to a team of 2 to 10 security experts to help you with the fixes.

Do I also get rescans after a vulnerability is fixed?

Yes, you get 1-3 rescans based on the type of Pentesting and the plan you opt for. You can avail these rescans within 30 days from the initial scan completion even after the vulnerabilities are fixed.

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Shikhil Sharma

Shikhil Sharma is the founder & CEO of Astra Security. Being involved with cybersecurity for over six years now, his vision is to make cyber security a 5-minute affair. Shikhil plays on the line between security and marketing. When not thinking about how to make Astra super simple, Shikhil can be found enjoying alternative rock or a game of football. Astra Security has been rewarded at Global Conference on Cyber Security by PM of India Mr. Narendra Modi. French President Mr. François Hollande also rewarded Astra under the La French Tech program. Astra Security is also a NASSCOM Emerge 50 company.

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