2.3.11.7 Ensure 'Network security: LAN Manager authentication level' is set to 'Send NTLMv2 response only. Refuse LM & NTLM'

Information

LAN Manager (LM) was a family of early Microsoft client/server software (predating Windows NT) that allowed users to link personal computers together on a single network.

LM network capabilities included transparent file and print sharing, user security features, and network administration tools.

In Active Directory domains, the Kerberos protocol is the default authentication protocol.

However, if the Kerberos protocol is not negotiated for some reason, Active Directory will use LM, NTLM, or NTLMv2.

LAN Manager authentication includes the LM, NTLM, and NTLM version 2 (NTLMv2) variants, and is the protocol that is used to authenticate all Windows clients when they perform the following operations: - Join a domain - Authenticate between Active Directory forests - Authenticate to down-level domains - Authenticate to computers that do not run Windows 2000, Windows Server 2003, or Windows XP - Authenticate to computers that are not in the domain The Network security: LAN Manager authentication level setting determines which challenge/response authentication protocol is used for network logons.

This choice affects the level of authentication protocol used by clients, the level of session security negotiated, and the level of authentication accepted by servers.

The recommended state for this setting is: 'Send NTLMv2 response only.

Refuse LM & NTLM'.

Solution

To establish the recommended configuration via GP, set the following UI path to: 'Send NTLMv2 response only.

Refuse LM & NTLM':

Computer Configuration\Policies\Windows Settings\Security Settings\Local Policies\Security Options\Network security: LAN Manager authentication level

See Also

https://workbench.cisecurity.org/files/1941

Item Details

Category: IDENTIFICATION AND AUTHENTICATION

References: 800-53|IA-5(6), CSCv6|13

Plugin: Windows

Control ID: 1be154501c288e335f7a657a21702f74932d799d76ec34917fbbf1c6bab2040b