Title

The Send download LanMan compatible password option is not set to Send NTLMv2 response only\refuse LM. (Cat I impact)

Discussion

The Kerberos v5 authentication protocol is the default for authentication of users who are logging on to domain accounts. NTLM is retained in later Windows versions for compatibility with clients and servers that are running earlier versions of Windows. It is also used to authenticate logons to stand-alone computers that are running later versions.

Check Content

Analyze the system using the Security Configuration and Analysis snap-in. Expand the Security Configuration and Analysis tree view. Navigate to Local Policies -> Security Options. If the value for “Network security: LAN Manager authentication level” is not set to at least “Send NTLMv2 response only\refuse LM” (Level 4), then this is a finding. The policy referenced configures the following registry value: Registry Hive: HKEY_LOCAL_MACHINE Registry Path: \System\CurrentControlSet\Control\Lsa\ Value Name: LmCompatibilityLevel Value Type: REG_DWORD Value: 4 (5 is also acceptable) Documentable Explanation: In a mixed Windows environment, if this setting needs to be loosened due to compatibility issues, then the reasons need to be documented with the IAO.

Fix Text

Configure the policy value for Computer Configuration -> Windows Settings -> Security Settings -> Local Policies -> Security Options -> “Network security: LAN Manager authentication level” to at least “Send NTLMv2 response only\refuse LM”.

Additional Identifiers

Rule ID: SV-1153r1_rule

Vulnerability ID: V-1153

Group Title: LanMan Authentication Level

Expert Comments

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