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V-241997

CAT I (High)

Windows Defender Firewall with Advanced Security must block unsolicited inbound connections when connected to a private network.

Rule ID

SV-241997r922944_rule

STIG

Microsoft Windows Defender Firewall with Advanced Security Security Technical Implementation Guide

Version

V2R2

CCIs

CCI-000382

Discussion

A firewall provides a line of defense against attack. To be effective, it must be enabled and properly configured. Unsolicited inbound connections may be malicious attempts to gain access to a system. Unsolicited inbound connections, for which there is no rule allowing the connection, will be blocked on a private network.

Check Content

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:  DefaultInboundAction

Type:  REG_DWORD
Value:  0x00000001 (1)

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:  DefaultInboundAction

Type:  REG_DWORD
Value:  0x00000001 (1)

Fix Text

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) >> Private Profile tab >> State, "Inbound connections" to "Block (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 privateprofile firewallpolicy blockinbound,allowoutbound".
or
"Netsh advfirewall set allprofiles firewallpolicy blockinbound,allowoutbound".

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