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Windows NT LAN Manager

What Does Windows NT LAN Manager Mean?

Windows NT LAN Manager (NTLM) is a security protocol suite for Microsoft Windows NT 4.0. NTLM replaced Windows LAN Manager (LANMAN). NTLM is used for down-level client and server compatibility up to Windows 2000.


NTLM was replaced by Microsoft Kerberos.

Techopedia Explains Windows NT LAN Manager

NTLM authenticates clients and servers via a challenge-response method composed of three messages, as follows:

  • Negotiation: Advertises capabilities
  • Challenge: Establishes identity
  • Authentication: Authenticates the client or server

NTLM uses one or more server-stored hashed passwords for authentication. Each password value is a 16-byte LM hash or NT hash. Microsoft does not recommend NTLM for current applications, due to weak encryption.


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