LAN Manager is a discontinued network operating system (NOS) available from multiple vendors and developed by Microsoft in cooperation with 3Com Corporation.
The LAN Manager OS/2 operating system was co-developed by IBM and Microsoft, using the Server Message Block (SMB) protocol.
[1] In 1990, Microsoft announced LAN Manager 2.0 with a host of improvements, including support for TCP/IP as a transport protocol for SMB, using NetBIOS over TCP/IP (NBT).
NTLM is used for logon with local accounts except on domain controllers since Windows Vista and later versions no longer maintain the LM hash by default.
It has for many years been considered good security practice to disable the compromised LM and NTLMv1 authentication protocols where they aren't needed.
Poor patching regimes subsequent to software releases supporting the feature becoming available have contributed to some organisations continuing to use LM Hashing in their environments, even though the protocol is easily disabled in Active Directory itself.