DNSExfiltrator allows for transfering (exfiltrate) a file over a DNS request covert channel. This is basically a data leak testing tool allowing to exfiltrate data over a covert channel.

DNSExfiltrator has two sides:

  1. The server side, coming as a single python script (dnsexfiltrator.py), which acts as a custom DNS server, receiving the file
  2. The client side (victim’s side), which comes in three flavors:

dnsExfiltrator.cs: C# script that can be compiled with csc.exe to provide a Windows managed executable

Invoke-DNSExfiltrator.ps1: PowerShell script providing the exact same functionalities by wrapping the dnsExfiltrator assembly

dnsExfiltrator.js: JScript script which is a conversion of the dnsExiltrator DLL assembly using DotNetToJScript, and providing the exact same functionalities

In order for the whole thing to work you must own a domain name and set the DNS record (NS) for that domain to point to the server that will run the dnsexfiltrator.py server side.

Features

DNSExfiltrator uses the system’s default DNS server, but you can define a specific one (useful for debugging purposes or for running the server side locally for instance). DNSExfiltrator supports basic RC4 encryption of the exfiltrated data, using the provided password to encrypt/decrypt the data.

DNSExfiltrator also provides some optional features to avoid detection:

  • requests throttling in order to stay more stealthy when exfiltrating data
  • reduction of the DNS request size (by default it will try to use as much bytes left available in each DNS request for efficiency)
  • reduction of the DNS label size (by default it will try to use the longest supported label size of 63 chars)

Dependencies

The only dependency is on the server side, as the dnsexfiltrator.py script relies on the external dnslib library. You can install it using pip:

Usage

SERVER SIDE

Start the dnsexfiltrator.py script passing it the domain name and decryption password to be used:

CLIENT SIDE

You can either use the compiled version, or the PowerShell wrapper (which is basically the same thing) or the JScript wrapper. In any case, the parameters are the same, with just a slight difference in the way of passing them in PowerShell.

1/ Using the C# compiled Windows executable (which you can find in the release directory):

DNSExfiltrator - Data Exfiltration Over DNS Request Covert Channel

2/ Using the PowerShell script, well, call it in any of your prefered way (you probably know tons of ways of invoking a powershell script) along with the script parameters. Most basic example:

Check the EXAMPLES section in the script file for further usage examples.

DNSExfiltrator - Data Exfiltration Over DNS Request Covert Channel

3/ Using the JScript script, pass it the exact same arguments as you would with the standalone Windows executable:

Or, with some options:

DNSExfiltrator - Data Exfiltration Over DNS Request Covert Channel

TODO

  • Some will ask for AES encryption instead of RC4, I know… might add it later
  • Display estimated transfer time
  • Do better argument parsing (I’m too lazy to learn how to use a c# argument parsing library, I wish it was as simple as Python)

DISCLAIMER

This tool is intended to be used in a legal and legitimate way only:

either on your own systems as a means of learning, of demonstrating what can be done and how, or testing your defense and detection mechanisms on systems you’ve been officially and legitimately entitled to perform some security assessments (pentest, security audits)

Quoting Empire’s authors: There is no way to build offensive tools useful to the legitimate infosec industry while simultaneously preventing malicious actors from abusing them.

Download DNSExfiltrator