SV-25105r2: The Lan Manager authentication level must be set to send NTLMv2 response only, and to refuse LM and NTLM. | Windows 7 Security Technical Implementation Guide

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Assessment Title

Rule Text

The Lan Manager authentication level must be set to send NTLMv2 response only, and to refuse LM and NTLM.

Description

Discussion Text

The Kerberos v5 authentication protocol is the default for authentication for domains. NTLM which is less secure, is retained in later Windows versions for compatibility with standalone systems as well as applications that may still use it. Earlier versions of the LM/NTLM protocol are particularly vulnerable to attack and must be prevented.

How this relates to the STIG checklist: STIG vs SCAP benchmark.

IA Controls

NIST SP 800-53

Not mappedCCI-000366CCE-8806-2

Additional Details

Responsibility

System Administrator

References

DPMS Target Windows 7 DISA DPMS Target Windows 7 1712

Checks

OVAL

oval:mil.disa.fso.windows:var:371500 ← xccdf_mil.disa.stig_value_lan_manager_authentication_level_var

SCC Automation Reference

The reconstructed evaluation script behind this rule's OVAL check(s) — every module a compound check combines, with this rule's own concrete values and DISA's SCC tool's real per-module mechanism curated from static teardown of SCC releases.

# Windows PowerShell
# Reconstructed from oval:mil.disa.fso.windows:def:3715
# The Lan Manager authentication level must be set to send NTLMv2 response only, and to refuse LM and NTLM.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.

# Verifies 'Network security: LAN Manager authentication level' is set to 'Send NTLMv2 response only. Refuse LM & NTLM' (Level 5)
# registry_object (registry_test)
function test_1 {
  return (((@{String='reg_sz';ExpandString='reg_expand_sz';Binary='reg_binary';DWord='reg_dword';MultiString='reg_multi_sz';QWord='reg_qword';None='reg_none'}[(Get-Item -Path 'Registry::HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa').GetValueKind('LmCompatibilityLevel').ToString()]) -eq 'reg_dword') -and (((Get-ItemProperty -Path 'Registry::HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa' -Name 'LmCompatibilityLevel' -ErrorAction SilentlyContinue) | Select-Object -ExpandProperty 'LmCompatibilityLevel') -eq 5))
}

if (test_1) {
  Write-Output "PASS"
} else {
  Write-Output "FAIL"
}

Assessment Script Powered by AISyntax-verified

A standalone PowerShell script to assess this control automatically. Review before running it in your environment.

Syntax-checked as valid PowerShell. Not executed here — running it for real needs the actual windows_7 target this check assesses.

# OVAL Definition: oval:mil.disa.fso.windows:def:3715
$compliant = (Get-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Control\Lsa' -Name 'LmCompatibilityLevel' -ErrorAction SilentlyContinue).LmCompatibilityLevel -eq 5
if ($compliant) { Write-Output "PASS"; Exit 0 } else { Write-Output "FAIL"; Exit 1 }

Remediation

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".