What is LAN Manager?
LAN Manager is a network operating system originally developed jointly by IBM and Microsoft. It supported the SMB protocol (Server Message Block) and at the time of its deployment enabled a very robust communication mode within a local area network (LAN). It has now been replaced by other types of communication within a LAN.
At the time of its publication in the late 1980s, LAN Manager was actually quite visionary. Microsoft's 1990 release of LAN Manager showed even more vision with the support of TCP / IP. LAN Manager became quite infamous over the years as its authentication mode became quite vulnerable to brute force and rainbow table attacks. Microsoft then replaced the LAN Manager hash with NTLM, but some security flaws remain. Microsoft has since supported the Kerberos authentication protocol, but continues to support LANMAN and NTLM for legacy systems.