SV-54890r3: The Windows Firewall with Advanced Security must allow outbound connections, unless a rule explicitly blocks the connection when connected to a private network. | Windows Firewall with Advanced Security Security Technical Implementation Guide

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Assessment Title

Rule Text

The Windows Firewall with Advanced Security must allow outbound connections, unless a rule explicitly blocks the connection when connected to a private network.

Description

Discussion Text

A firewall provides a line of defense against attack. To be effective, it must be enabled and properly configured. Outbound connections are allowed on a private network, unless a rule explicitly blocks the connection. This allows normal outbound communication, which could be restricted as necessary with additional rules.

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

IA Controls

NIST SP 800-53

Not mappedCCI-001094

References

DPMS Target Windows Firewall with Advanced Security DISA DPMS Target Windows Firewall with Advanced Security 2565

Checks

OVAL

oval:mil.disa.fso.windows:var:481000 ← xccdf_mil.disa.stig_value_private_profile_outbound_connections_var
oval:mil.disa.fso.windows:var:479900 ← xccdf_mil.disa.stig_value_private_profile_firewall_state_var

DISA STIG (Manual Reference)

If the firewall's Private Profile is not enabled (see V-17416), this requirement is also a finding.

If the following policy-based registry value exists and is not configured as specified, this is a finding.

Registry Hive:  HKEY_LOCAL_MACHINE
Registry Path:  \SOFTWARE\Policies\Microsoft\WindowsFirewall\PrivateProfile\

Value Name:  DefaultOutboundAction

Type:  REG_DWORD
Value:  0x00000000 (0)

If the policy-based registry value does not exist, verify the following registry value. If it is not configured as specified, this is a finding.

Registry Hive:  HKEY_LOCAL_MACHINE
Registry Path:  \SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\

Value Name:  DefaultOutboundAction

Type:  REG_DWORD
Value:  0x00000000 (0)

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:4810
# The Windows Firewall with Advanced Security must allow outbound connections, unless a rule explicitly blocks the connection when connected to a private network.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.

# HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\WindowsFirewall\PrivateProfile!DefaultOutboundAction value equals variable
# 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\SOFTWARE\Policies\Microsoft\WindowsFirewall\PrivateProfile').GetValueKind('DefaultOutboundAction').ToString()]) -eq 'reg_dword') -and (((Get-ItemProperty -Path 'Registry::HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\WindowsFirewall\PrivateProfile' -Name 'DefaultOutboundAction' -ErrorAction SilentlyContinue) | Select-Object -ExpandProperty 'DefaultOutboundAction') -eq 0))
}
# HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\WindowsFirewall\PrivateProfile!DefaultOutboundAction non existent
# registry_object (registry_test)
function test_2 {
  return (-not ($null -ne (Get-ItemProperty -Path 'Registry::HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\WindowsFirewall\PrivateProfile' -Name 'DefaultOutboundAction')))
}
# HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile value equals variable
# registry_object (registry_test)
function test_3 {
  return (((@{String='reg_sz';ExpandString='reg_expand_sz';Binary='reg_binary';DWord='reg_dword';MultiString='reg_multi_sz';QWord='reg_qword';None='reg_none'}[(Get-Item -Path 'Registry::HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile').GetValueKind('DefaultOutboundAction').ToString()]) -eq 'reg_dword') -and (((Get-ItemProperty -Path 'Registry::HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile' -Name 'DefaultOutboundAction' -ErrorAction SilentlyContinue) | Select-Object -ExpandProperty 'DefaultOutboundAction') -eq 0))
}
# HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\WindowsFirewall\PrivateProfile!EnableFirewall value equals variable
# registry_object (registry_test)
function test_4 {
  return (((@{String='reg_sz';ExpandString='reg_expand_sz';Binary='reg_binary';DWord='reg_dword';MultiString='reg_multi_sz';QWord='reg_qword';None='reg_none'}[(Get-Item -Path 'Registry::HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\WindowsFirewall\PrivateProfile').GetValueKind('EnableFirewall').ToString()]) -eq 'reg_dword') -and (((Get-ItemProperty -Path 'Registry::HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\WindowsFirewall\PrivateProfile' -Name 'EnableFirewall' -ErrorAction SilentlyContinue) | Select-Object -ExpandProperty 'EnableFirewall') -eq 1))
}
# HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\WindowsFirewall\PrivateProfile!EnableFirewall non existent
# registry_object (registry_test)
function test_5 {
  return (-not ($null -ne (Get-ItemProperty -Path 'Registry::HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\WindowsFirewall\PrivateProfile' -Name 'EnableFirewall')))
}
# HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile!EnableFirewall value equals variable
# registry_object (registry_test)
function test_6 {
  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\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile').GetValueKind('EnableFirewall').ToString()]) -eq 'reg_dword') -and (((Get-ItemProperty -Path 'Registry::HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile' -Name 'EnableFirewall' -ErrorAction SilentlyContinue) | Select-Object -ExpandProperty 'EnableFirewall') -eq 1))
}

if (-not (((test_1 -or (test_2 -and test_3)) -and (test_4 -or -not ((test_5 -and test_6)))))) {
  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_firewall target this check assesses.

# OVAL Definition: oval:mil.disa.fso.windows:def:4810
if (!(Get-ItemProperty -Path "HKLM:\SOFTWARE\Policies\Microsoft\WindowsFirewall\PrivateProfile" -ErrorAction SilentlyContinue).DefaultOutboundAction -eq 0 -or (Test-Path -Path "HKLM:\SOFTWARE\Policies\Microsoft\WindowsFirewall\PrivateProfile\DefaultOutboundAction" -and (Get-ItemProperty -Path "HKLM:\SOFTWARE\Policies\Microsoft\WindowsFirewall\PrivateProfile" -ErrorAction SilentlyContinue).DefaultOutboundAction -eq 0) -or (Test-Path -Path "HKLM:\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile" -and (Get-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile" -ErrorAction SilentlyContinue).DefaultOutboundAction -eq 0)) { Write-Output "FAIL"; Exit 1 } else { Write-Output "PASS"; Exit 0 }

Remediation

The preferred method of configuring the firewall settings is with a policy, particularly in a domain environment.

Configure the policy value for Computer Configuration -> Windows Settings -> Security Settings -> Windows Firewall with Advanced Security -> Windows Firewall with Advanced Security -> Windows Firewall Properties (this link will be in the right pane) -> Private Profile Tab -> State, "Outbound connections" to "Allow (default)".

In addition to using policies, systems may also be configured using the firewall GUI or Netsh commands.  These methods may be more appropriate for standalone systems.
The configuration settings in the GUI are the same as those specified in the policy above.  Windows Firewall Properties will be a link in the center pane after opening Windows Firewall with Advanced Security.

The following Netsh commands may also be used to configure this setting:
"Netsh advfirewall set privateprofile firewallpolicy blockinbound,allowoutbound".
Or
"Netsh advfirewall set allprofiles firewallpolicy blockinbound,allowoutbound".
Both inbound and outbound parameters must be specified to execute this command.