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

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-242003	WNFWA-000021	SV-242003r922956_rule		Medium

Description
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 public network, unless a rule explicitly blocks the connection. This allows normal outbound communication, which could be restricted as necessary with additional rules.

STIG	Date
Microsoft Windows Defender Firewall with Advanced Security Security Technical Implementation Guide	2023-08-23

Details

Check Text ( C-45278r698248_chk )
If the firewall's Public Profile is not enabled (see V-17417), 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\PublicProfile\ 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\PublicProfile\ Value Name: DefaultOutboundAction Type: REG_DWORD Value: 0x00000000 (0)

Check Text ( C-45278r698248_chk )

If the firewall's Public Profile is not enabled (see V-17417), 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\PublicProfile\

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\PublicProfile\

Value Name: DefaultOutboundAction

Type: REG_DWORD
Value: 0x00000000 (0)

Fix Text (F-45237r922955_fix)
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 Defender Firewall with Advanced Security >> Windows Defender Firewall with Advanced Security >> Windows Defender Firewall Properties (this link will be in the right pane) >> Public 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. Microsoft Defender Firewall Properties will be a link in the center pane after opening Microsoft Defender Firewall with Advanced Security. The following Netsh commands may also be used to configure this setting: "Netsh advfirewall set publicprofile firewallpolicy blockinbound,allowoutbound". or "Netsh advfirewall set allprofiles firewallpolicy blockinbound,allowoutbound". Both inbound and outbound parameters must be specified to execute this command.

Fix Text (F-45237r922955_fix)

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 Defender Firewall with Advanced Security >> Windows Defender Firewall with Advanced Security >> Windows Defender Firewall Properties (this link will be in the right pane) >> Public 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. Microsoft Defender Firewall Properties will be a link in the center pane after opening Microsoft Defender Firewall with Advanced Security.

The following Netsh commands may also be used to configure this setting:

"Netsh advfirewall set publicprofile firewallpolicy blockinbound,allowoutbound".
or
"Netsh advfirewall set allprofiles firewallpolicy blockinbound,allowoutbound".

Both inbound and outbound parameters must be specified to execute this command.