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

If the following registry value does not exist or is not configured as specified, this is a finding: 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-225507r569185_rule

Vulnerability ID: V-225507

Group Title: SRG-OS-000480-GPOS-00227

Expert Comments

CCIs tied to check.

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