What is NTLMv1? NTLMv1 (NT LAN Manager version 1) is a Microsoft authentication protocol used primarily for network authentication on Windows-based systems. It is a challenge-response authentication protocol, where the server sends a challenge to the client, which is then encrypted using the client’s password hash and sent back to the server for authentication. NTLM … Continue reading NTLM v1 and NTLM v2 vs Kerberos