Information
The socketfilter Firewall is what is used when the Firewall is turned on in the Security & Privacy Preference Pane. In order to appropriately monitor what access is allowed and denied, logging must be enabled.The logging level must be set to "detailed" to be useful in monitoring connection attempts that the firewall detects. Throttled login is not sufficient for examining Firewall connection attempts.
In depth log monitoring on macOS may require changes to the "Enable-Private-Data" key in SystemLogging.System to ensure more complete logging.
Reviewing macOS Unified Logs
In order to troubleshoot the successes and failures of a Firewall, detailed logging should be enabled.
Solution
Terminal Method:
Run the following command to enable logging of the firewall:
$ /usr/bin/sudo /usr/libexec/ApplicationFirewall/socketfilterfw --setloggingmode on
Turning on log mode
$ /usr/bin/sudo /usr/libexec/ApplicationFirewall/socketfilterfw --setloggingopt detail
Setting detail log option
Impact:
Detailed logging may result in excessive storage.
Item Details
Category: AUDIT AND ACCOUNTABILITY, SYSTEM AND COMMUNICATIONS PROTECTION
References: 800-53|AU-2, 800-53|AU-3, 800-53|AU-3(1), 800-53|AU-7, 800-53|AU-12, 800-53|SC-7, 800-53|SC-7(5), CSCv7|6.2, CSCv7|6.3, CSCv7|9.2
Control ID: 4b5ff9b20e7e1824128998648a2f6c9e1d6cf27d88a30b40bab61f6cf1c1c2e3