High Quality Content by WIKIPEDIA articles! NTLMSSP (NT LAN Manager Security Support Provider) is a binary messaging protocol used by the Microsoft Security Support Provider Interface (SSPI) to facilitate NTLM challenge-response authentication and to negotiate integrity and confidentiality options. NTLMSSP is used wherever SSPI authentication is used including, but not limited to, Server Message Block/CIFS extended security authentication, HTTP Negotiate authentication (e.g. IIS with IWA turned on) and MSRPC services.