16 January

Responder – Comprehensive Guide

Note:
The guides provided in this article are comprehensive overviews designed to give a solid understanding of the topics covered. While they include detailed instructions and best practices, they are not intended to serve as complete tutorials for every aspect of the subject. Readers are encouraged to explore additional resources and documentation for in-depth knowledge and specific implementations. Always exercise caution and ensure compliance with applicable laws and ethical guidelines when applying the information shared in these guides.

What is Responder?

Responder is a powerful tool used in network penetration testing to capture and relay NTLM hashes via LLMNR, NBT-NS, and MDNS poisoning. It is widely used by red teamers to perform man-in-the-middle attacks within internal networks to obtain credentials and escalate privileges.


Installation & Setup

System Requirements

Recommended OS: Linux-based systems (Kali Linux, Parrot OS, Ubuntu, Debian, Arch, NixOS)
Dependencies: Python

Install Responder

Using APT (Debian-based systems)

sudo apt update && sudo apt install responder

Using GitHub (Latest Version for Any Linux OS)

git clone https://github.com/lgandx/Responder.git
cd Responder
sudo python3 Responder.py -h

Basic Usage of Responder

Start Responder on a Specific Interface

sudo python3 Responder.py -I eth0

Analyze Captured Hashes

cat Responder-Session.log

Enable SMB & HTTP Authentication Relaying

sudo python3 Responder.py -I eth0 -wF

Alternatives to Responder

Inveigh – A .NET equivalent for Windows environments
MITMf – Man-in-the-Middle attack framework
Bettercap – Versatile network attack tool
Ettercap – Traditional MITM attack tool


Advanced Responder Techniques

  • WPAD Attack – Exploiting proxy auto-discovery settings
  • NTLM Relay Attack – Relaying captured hashes for privilege escalation
  • Custom Poisoning Rules – Fine-tuning responses for better stealth

Red Teaming Best Practices with Responder

Run on isolated VLANs for stealth.
Combine with NTLM relay tools like ntlmrelayx.
Modify Responder.conf to avoid unnecessary noise.
Leverage WPAD exploitation for proxy authentication attacks.


Blue Team’s Advanced Hunting Techniques

Monitor unusual LLMNR/NBT-NS requests on the network.
- Disable LLMNR and NBT-NS if not required.
- Use network segmentation to reduce exposure.
- Deploy host-based firewall rules to restrict SMB communication.


Detection & Countermeasures (Blue Team Perspective)

- Enable SMB signing to prevent NTLM relay attacks.
- Monitor endpoint logs for repeated authentication failures.
- Use Sysmon and Splunk for in-depth analysis of poisoning attempts.
- Implement conditional access policies for privileged accounts.


Best Practices for Ethical Use

✔ Always obtain permission before using Responder in an environment.
✔ Follow ethical hacking guidelines and responsible disclosure policies.
Test in a controlled lab to understand tool behavior before deploying.
Stay updated with the latest versions to ensure reliability and effectiveness.





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