Configure the Windows Defender Firewall with Advanced Security Log
To configure Windows Defender Firewall with Advanced Security to log dropped packets or successful connections, use the Windows Defender Firewall with Advanced Security node in the Group Policy Management MMC snap-in.
To complete these procedures, you must be a member of the Domain Administrators group, or otherwise be delegated permissions to modify the GPOs.
To configure the Windows Defender Firewall with Advanced Security log
Open the Group Policy Management Console to Windows Defender Firewall with Advanced Security.
In the details pane, in the Overview section, click Windows Defender Firewall Properties.
For each network location type (Domain, Private, Public), perform the following steps.
Click the tab that corresponds to the network location type.
Under Logging, click Customize.
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 type the path to the new location, or click Browse to select a file location.
Important: The location you specify must have permissions assigned that permit the Windows Defender Firewall service to write to the log file.
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 type in 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.
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.
Click OK twice.
Troubleshooting Slow Log Ingestion
If logs are slow to appear in Sentinel, you can turn down the log file size. Just beware that this downsizing will result in more resource usage due to the increased resource usage for log rotation.