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Friday, August 22, 2014

Windows Filtering Platform events in Security Log ...OR... Don't Screw with Advanced Audit Policy Configuration

I have 4 domain controllers, and the are set up to forward events in their Security Logs to a Kiwi Syslog Server (Solarwinds). I have a 30 day rotation, and I monitor the space usage in a dedicated pie chart on my heads-up display. This past week it started getting lower. After poking around, I noticed that the file sizes of each days' log files were getting bigger and bigger. I opened one up in the Kiwi log viewer (which is the most horrible part of this software, by the way), and noticed a TON of messages from "Windows Filtering Platform". These were basically noting success every time an event was sent to the syslog server. Well..... thanks I guess?

I rarely have to deal with auditing, so I consult the Google and find instructions for how to stop success auditing for Windows Filtering Platform Events. It seemed straight forward enough: Open you default domain controller group policy, and drill down into the Advanced Audit Policy Configuration, and there are two options there dedicated to it. I enable the auditing policy and check neither success or deny, so that the policy will be in effect and tell Windows auditing not to monitor either of them. I document my changes in the ticket I made for myself and close it out.

A few minutes later I get an email from our Netwrix AD auditing software telling me that auditing isn't configured correctly. I go into Active Directory Users and Computers, add a period to the end of a computer account's description, and run a new report. The change is noted, but there are big red warning letters telling me something with auditing isn't right. Huh. I decide to see what the overnight report says, make another benign change in ADUC, and head out for the day.

The next morning, the report comes in showing changes in AD, but it still has big red warning letters saying that auditing isn't configured correctly. I go to check my syslog file size, and it's 5KB (down from 4GB), and the only thing in there are messages over and over saying that the audit settings have been changed.

So, back to Google, and APPARENTLY, when you use any part of the Advanced Audit Policy Configuration, it supercedes ALL of the normal auditing settings. So, by simply turning off logging for the Windows Filtering Platform, I had negated all settings in the regular auditing settings. Super.

Now, I don't know if you've ever had to reverse a group policy setting, but it is not intuitive. Simply turning the setting off does not reverse what has been done. A group policy restore from backup cannot reverse what you have done; you actually need to reverse the setting. Likewise, clearing the checkboxes in the advanced auditing section would not restore auditing to the way it used to be. Sadly.

Here is what I had to do to reverse this calamity:

  1. Put the GPO back to the way it was.
  2. Get on a domain controller.
  3. Find out what you Group Policy Object's policyID is. I used get-gpo -name "<name>".
  4. Now, go to C:\Windows\SYSVOL\Domain\Policies\<PolicyID>\Machine\Microsoft\Windows NT
  5. In this folder delete the Audit folder. 
  6. Now get on a command shell, and type the following: auditpol /get /category:*
  7. What you see is that nothing is being audited.
  8. Run a gpupdate /force, then run the command again - SUCCESS!!!

While researching this I ran across the command that I should have used to get rid of those Windows Filtering Platform events, which is this:
auditpol /set /subcategory:"Filtering Platform Connection" /Success:disable

You can check the setting before and after you run that command with this command:
auditpol /get /subcategory:"Filtering Platform Connection"

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