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DNS Enumeration Using Python

As a penetration tester or red teamer, it is imperative that we understand the tools that we use inside and out and also have the ability to write out own, even simple, tools if we are on an assessment with certain constraints such as no internet or the requirement to use a customer provided host as our "attack box." A strong understanding of DNS as well as the various ways to interact with fundamental when performing any security assessment.

4.07

Created by Cry0l1t3

Medium General

Summary

This module covers the importance of tool development for technical security practitioners, using the DNS protocol as examples for the tool building exercises.

In this module, we will cover:

  • An introduction to tool development
  • DNS structure
  • Querying DNS records
  • Tool development using Python modules
  • DNS security

This module is broken down into sections with accompanying hands-on exercises to practice each of the tactics and techniques we cover. The module ends with a practical hands-on skills assessment to gauge your understanding of the various topic areas.

As you work through the module, you will see example commands and command output for the various topics introduced. It is worth reproducing as many of these examples as possible to reinforce further the concepts introduced in each section. You can do this in the Pwnbox provided in the interactive sections or your own virtual machine.

You can start and stop the module at any time and pick up where you left off. There is no time limit or "grading," but you must complete all of the exercises and the skills assessment to receive the maximum number of cubes and have this module marked as complete in any paths you have chosen.

The module is classified as "Medium" but assumes a working knowledge of the Linux command line and an understanding of information security fundamentals.

A firm grasp of the following modules can be considered prerequisites for successful completion of this module:

  • Linux Fundamentals
  • Web Requests
  • Introduction to Bash Scripting

Tool Development

The development of tools has many advantages. Besides the fact that we practice and learn specific programming languages during the development process, we also understand how such programs are developed and how the communication between server and client works. This gives us a better understanding of the structures of programs and some repertoire, which will help us understand the processes faster and easier.

It is necessary to have this understanding to think outside the box and try out potential weaknesses in the program that may be present. Finally, developers also have difficulties with development, which often leads to program vulnerabilities. This could be certain functions, libraries, or even the handling of specific values.

In the next sections, we will get back to DNS and dive a little deeper. Most probably, we have already dealt with some DNS records and know what information they can provide. Working with some tools and resources is a standard approach, but it is always best to use a tool that we have written and know precisely what it does and how.

Before we start to develop our tool, we need the information we want to work with. Therefore it is essential to understand every step of the interaction with the server to track and reproduce it. To get or query this information, we need to understand how the communication between the services, in this case, DNS, works, and how it is structured.

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