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.


Related Terms

Margaret Rouse

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.