NTLM

NTLM is a native windows authentication mechanism. Please find the relevant info in below link

 

https://msdn.microsoft.com/en-us/library/windows/desktop/aa378749(v=vs.85).aspx

 

Hello Shri,

 

NTLM or NT Lan Manager is an authentication protocol.

 

There are many authentication protocols such as Basic, Radius, Kerberos,... used in windows network to authenticate users/machines.

 

NTLM belongs to the "challenge/response" protocol family, which means that :

 

1.First, the client sends to the server a NEGOTIATE_MESSAGE

 

2.The server responds with CHALLENGE_MESSAGE

 

3.Finally, the client responds to the challenge with an AUTHENTICATE_MESSAGE

 

For more details you can check on internet there are many articles about this protocol.