Hello, aspiring ethical hackers. In our previous blogpost, you learnt how Windows authentication works. In this article, you will learn about chntpw, a offline Windows password and Registry Editor that can be used to reset or blank local passwords on Windows NT operating systems.

Chntpw or Change NT Password is a utility that does the above actions by editing the SAM database where Windows stores its hashes.

Let’s see how this tool works. We can use this tool in two ways. The first method is using it as a package installed in cybersecurity operating systems like Kali, Parrot Security etc. The second method is via a bootable CD/USB image. For this tutorial, we will be using the bootable CD/USB image. It can be downloaded from here.

Using chntpw, we can reset local account passwords of all NT Windows operating systems like Windows NT, 2000, XP, Vista , Windows 7 , windows 8, windows Server 2003 and 2008 etc. We will test this tool on Windows XP SP2.

After making a bootable USB from files downloaded, insert the bootable USB drive of chntpw and power on into BIOS. You should use the screen shown below.

Hit ENTER. You should see the screen shown below.

Then, it will show you all the steps to take (total 4 steps). In the first step, you have to select the disk you want to make changes to (The disk on which Windows is installed). In our case, it is disk “sdb”. It will automatically show you disk partitions. All you have to do is select. It will automatically also find Windows installations and show it to you. In this example, there is only one disk set.

Select ‘1’. The disk will be mounted. The second step is to select the registry files you want to make changes to. It will prompt you to select the part of registry you want to make changes to from the predefined choices listed. The options given are,
1. Password reset
2. Recovery/ console parameters (software).
3. Loading almost all registry files.

For this tutorial, let’s select the option of “password reset”. Then SAM file will be loaded to the /tmp directory. In the third step, more options are shown as shown below.

Let’s select the option of “Edit user data and passwords”. Then it will list all the users present on the local system.

Then it will ask you to select the “RID” of the user you want to make changes to. Let’s select the user with RID ‘rf4’, the Administrator user. Once you select the user, it will present the ‘User edit’ menu asking you to select what changes you want to make.

Let’s select the option to clear the password (making blank). Then, it will automatically blank the password of the user. Changes are made but not written to the disk yet. Type ‘q’ to quit the menu.

The fourth step is to write the changes to the disk. The tool will prompt you asking if you want to write changes to the disk. Select ‘Yes’ to do it.

That’s how you can use chntpw to change or blank passwords of local Windows users.  

Hello, aspiring ethical hackers. In this article, you will learn about Responder tool, a tool that is helpful in harvesting credentials and passwords on the target network. It is useful mostly in internal penetration testing of services.

What is Responder?

Responder is a LLMNR, NBT-NS and MDNS poisoner with a built in HTTP, SMB, MSSQL, FTP, LDAP rogue authentication servers. It harvests credentials and password hashes by answering to specific NBT-NS (NetBIOS Name Service queries). The goal of responder is to stay stealthy on the network without making much noise.

Let’s see how this tool works. For this, we will be using Kali Linux as attacker system as Responder is installed by default on it. We are performing this tutorial in an Active Directory Hacking Lab. In this lab, Windows 10 is a client system (although any other Windows OS will do), PFSense firewall acts as gateway and firewall and Windows Server 2016 is the server. To use Responder on Kali , Kali Linux needs to be connected to the LAN network in the Active Directory. i.e the internal network.

Kali Linux, the attacker system however need not be joined to the domain. But it will still collect password hashes below belong to users in the network. In real-world scenarios, Responder tool is uploaded to the target system or network.

Once Kali is connected to the internal network, all you have to do is to start Responder on the interface you want as shown below.

sudo responder -I <network_interface>

For example, here are are starting it on interface eth1 where our target domain network is connected.

It starts poisoners and servers as shown below.

Now, all we have to do is WAIT for any user in the network to do a mistake. For example, lets say a user of the organization tries to access a local network share “LOOKRECKAH” and makes a mistake while doing it as shown below. He wants to access network share “LOOKRECKAH” but hits ‘ENTER’ after only typing “LOOK”.

As soon as he does that, he is prompted for his network credentials. This is done by Responder tool.

However, there is no need for any credentials. Responder already logs lots of traffic on the attackers machine i.e. kali.

While we scroll down the traffic, we can see password hash of that user and his username.

While waiting patiently, we can also grab credentials of different users.

All this information is stored by Responder in the /usr/share/responder/logs directory on Kali.

In this directory, credentials and hashes are stored in text files.

Analysis mode

Responder has different modes of operation. Analysis mode is one such mode. In this mode, Responder allows users to see NBT-NS, BROWSER, LLMNR and DNS requests on the network but doesn’t perform any poisoning. Analysis mode can be started using command shown below.

sudo responder -I <interface_name> -A

This mode can still reveal some information about the network.

Using WPAD Proxy Server

WPAD stands for Web Proxy Auto-Discovery protocol. Organizations often make their users connect to a web server through proxies. WPAD allows web browsers and other clients to automatically discover the URL of a proxy server pac files. You can use responder tool to poison these web requests as shown below. WPAD proxy can be started on Responder using command show below.

sudo responder -I <interface_name> -wd

As you can see in the above image, WPAD proxy is on. Now, when a employee of an organization tries to access the internal website and mistypes it on a browser, he will be prompted with a credential screen as shown below.

When he enters his credentials assuming it to be a genuine prompt

We get the user’s password hashes as shown below.

That’s all in Responder tool for now.