The NTLM (Windows NT LAN Manager) authentication scheme is the
authentication algorithm used by Microsoft.

NTLM authentication scheme is used in DCOM and HTTP environment. It is
used to authenticate DCE RPC packets in DCOM. It is also used to
authenticate HTTP packets to MS Web Proxy or MS Web Server.

Currently, it is the authentication scheme Internet Explorer chooses to
authenticate itself to proxies/web servers that supports NTLM.