Configure Windows Firewall logging

• Gäller för:

  ✅ Windows 11, ✅ Windows 10, ✅ Windows Server 2022, ✅ Windows Server 2019, ✅ Windows Server 2016

To configure Windows Firewall to log dropped packets or successful connections, you can use:

• Configuration Service Provider (CSP), using an MDM solution like Microsoft Intune
• Group policy (GPO)

The following instructions provide details how to configure your devices. Select the option that best suits your needs.

Intune/CSP

1. Sign into the Microsoft Intune admin center
2. Go to Endpoint security > Firewall > Create policy > Windows 10, Windows 11, and Windows Server > Windows Firewall > Create
3. Enter a name and, optionally, a description > Next
4. Under Configuration settings, for each network location type (Domain, Private, Public), configure:
   • Log file path
   • Enable log dropped packets
   • Enable log success connections
   • Log max file size
5. Select Next > Next
6. Assign the policy to a group that contains as members the devices or users that you want to configure > Next > Create

Tip

If you prefer you can also use a Settings catalog policy to configure Windows Firewall logging.

Alternatively, you can configure devices using a custom policy with the Firewall CSP.

Network profile	Setting
Domain	Setting name: EnableLogDroppedPackets OMA-URI: ./Vendor/MSFT/Firewall/MdmStore/DomainProfile/EnableLogDroppedPackets
Domain	Setting name: LogFilePath OMA-URI: ./Vendor/MSFT/Firewall/MdmStore/DomainProfile/LogFilePath
Domain	Setting name: EnableLogSuccessConnections OMA-URI: ./Vendor/MSFT/Firewall/MdmStore/DomainProfile/EnableLogSuccessConnections
Domain	Setting name: LogMaxFileSize OMA-URI: ./Vendor/MSFT/Firewall/MdmStore/DomainProfile/LogMaxFileSize
Private	Setting name: EnableLogDroppedPackets OMA-URI: ./Vendor/MSFT/Firewall/MdmStore/PrivateProfile/EnableLogDroppedPackets
Private	Setting name: LogFilePath OMA-URI: ./Vendor/MSFT/Firewall/MdmStore/PrivateProfile/LogFilePath
Private	Setting name: EnableLogSuccessConnections OMA-URI: ./Vendor/MSFT/Firewall/MdmStore/PrivateProfile/EnableLogSuccessConnections
Private	Setting name: LogMaxFileSize OMA-URI: ./Vendor/MSFT/Firewall/MdmStore/PrivateProfile/LogMaxFileSize
Public	Setting name: EnableLogDroppedPackets OMA-URI: ./Vendor/MSFT/Firewall/MdmStore/PublicProfile/EnableLogDroppedPackets
Public	Setting name: LogFilePath OMA-URI: ./Vendor/MSFT/Firewall/MdmStore/PublicProfile/LogFilePath
Public	Setting name: EnableLogSuccessConnections OMA-URI: ./Vendor/MSFT/Firewall/MdmStore/PublicProfile/EnableLogSuccessConnections
Public	Setting name: LogMaxFileSize OMA-URI: ./Vendor/MSFT/Firewall/MdmStore/PublicProfile/LogMaxFileSize

GPO

To configure a device with group policy, use the Local Group Policy Editor. To configure multiple devices joined to Active Directory, create or edit a group policy object (GPO) and use the following settings:

1. Expand the nodes Computer Configuration > Policies > Windows Settings > Security Settings > Windows Firewall with Advanced Security
2. In the details pane, in the Overview section, select Windows Defender Firewall Properties
3. For each network location type (Domain, Private, Public), perform the following steps
   1. Select the tab that corresponds to the network location type
   2. Under Logging, select Customize
   3. The default path for the log is %windir%\system32\logfiles\firewall\pfirewall.log. If you want to change this path, clear the Not configured check box and enter the path to the new location, or select Browse to select a file location
4. The default maximum file size for the log is 4,096 kilobytes (KB). If you want to change this size, clear the Not configured check box, and enter the new size in KB, or use the up and down arrows to select a size. The file won't grow beyond this size; when the limit is reached, old log entries are deleted to make room for the newly created ones.
5. No logging occurs until you set one of following two options:
   • To create a log entry when Windows Defender Firewall drops an incoming network packet, change Log dropped packets to Yes
   • To create a log entry when Windows Defender Firewall allows an inbound connection, change Log successful connections to Yes
6. Select OK twice

Group policies can be linked to domains or organizational units, filtered using security groups, or filtered using WMI filters.

Important

The location you specify must have permissions assigned that permit the Windows Firewall service to write to the log file.

Recommendations

Here are some recommendations for configuring Windows Firewall logging:

• Change the logging size to at least 20,480 KB (20 MB) to ensure that the log file doesn't fill up too quickly. The maximum log size is 32,767 KB (32 MB)
• For each profile (Domain, Private, and Public) change the default log file name from %windir%\system32\logfiles\firewall\pfirewall.log to:
  • %windir%\system32\logfiles\firewall\pfirewall_Domain.log
  • %windir%\system32\logfiles\firewall\pfirewall_Private.log
  • %windir%\system32\logfiles\firewall\pfirewall_Public.log
• Log dropped packets to Yes
• Log successful connections to Yes

On a single system, you can use the following commands to configure logging:

netsh advfirewall>set allprofiles logging allowedconnections enable
netsh advfirewall>set allprofiles logging droppedconnections enable

Parsing methods

There are several methods to parse the Windows Firewall log files. For example:

• Enable Windows Event Forwarding (WEF) to a Windows Event Collector (WEC). To learn more, see Use Windows Event Forwarding to help with intrusion detection
• Forward the logs to your SIEM product such as our Azure Sentinel. To learn more, see Windows Firewall connector for Microsoft Sentinel
• Forward the logs to Azure Monitor and use KQL to parse the data. To learn more, see Azure Monitor agent on Windows client devices

Tip

If logs are slow to appear in your SIEM solution, you can decrease the log file size. Just beware that the downsizing results in more resource usage due to the increased log rotation.

Troubleshoot if the log file is not created or modified

Sometimes the Windows Firewall log files aren't created, or the events aren't written to the log files. Some examples when this condition might occur include:

• Missing permissions for the Windows Defender Firewall Service (mpssvc) on the folder or on the log files
• You want to store the log files in a different folder and the permissions are missing, or aren't set automatically
• if firewall logging is configured via policy settings, it can happen that
  • the log folder in the default location %windir%\System32\LogFiles\firewall doesn't exist
  • the log folder in a custom path doesn't exist

In both cases, you must create the folder manually or via script, and add the permissions for mpssvc.

New-Item -ItemType Directory -Path $env:windir\System32\LogFiles\Firewall

Verify if mpssvc has FullControl on the folder and the files. From an elevated PowerShell session, use the following commands, ensuring to use the correct path:

$LogPath = Join-Path -path $env:windir -ChildPath "System32\LogFiles\Firewall"
(Get-ACL -Path $LogPath).Access | Format-Table IdentityReference,FileSystemRights,AccessControlType,IsInherited,InheritanceFlags -AutoSize

The output should show NT SERVICE\mpssvc having FullControl:

IdentityReference      FileSystemRights AccessControlType IsInherited InheritanceFlags
-----------------      ---------------- ----------------- ----------- ----------------
NT AUTHORITY\SYSTEM         FullControl             Allow       False    ObjectInherit
BUILTIN\Administrators      FullControl             Allow       False    ObjectInherit
NT SERVICE\mpssvc           FullControl             Allow       False    ObjectInherit

If not, add FullControl permissions for mpssvc to the folder, subfolders and files. Make sure to use the correct path.

$LogPath = Join-Path -path $env:windir -ChildPath "System32\LogFiles\Firewall"
$NewAcl = Get-Acl -Path $LogPath 

$identity = "NT SERVICE\mpssvc"
$fileSystemRights = "FullControl"
$inheritanceFlags = "ContainerInherit,ObjectInherit"
$propagationFlags = "None"
$type = "Allow"

$fileSystemAccessRuleArgumentList = $identity, $fileSystemRights, $inheritanceFlags, $propagationFlags, $type
$fileSystemAccessRule = New-Object -TypeName System.Security.AccessControl.FileSystemAccessRule -ArgumentList $fileSystemAccessRuleArgumentList

$NewAcl.SetAccessRule($fileSystemAccessRule)
Set-Acl -Path $LogPath -AclObject $NewAcl

Restart the device to restart the Windows Defender Firewall service.