Title

The LanMan authentication level must be set to send NTLMv2 response only, and to refuse LM and NTLM. (Cat I impact)

Discussion

The Kerberos v5 authentication protocol is the default for authentication of users who are logging on to domain accounts. NTLM which is less secure, is retained in later Windows versions for compatibility with clients and servers that are running earlier versions of Windows or applications that still use it. 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. (See "Performing Analysis with the Security Configuration and Analysis Snap-in" in the STIG Overview document.) 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 "Send NTLMv2 response only. Refuse LM & NTLM" (Level 5), 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: 5

Fix Text

Configure the policy value for Computer Configuration -> Windows Settings -> Security Settings -> Local Policies -> Security Options -> "Network security: LAN Manager authentication level" to "Send NTLMv2 response only. Refuse LM & NTLM".

Additional Identifiers

Rule ID: SV-48048r1_rule

Vulnerability ID: V-1153

Group Title: LanMan Authentication Level

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.