Running an enterprise application on a Windows Server 2012 R2, the system suddenly became very slow: some huge load was hitting the disk. Deeper inspection has shown that svchost.exe (LocalServiceNetworkRestricted) is constantly writing around 25Mb per second to
C:\Windows\System32\winevt\Logs\Security.evtx file.
At the same time, Windows EventLog gets spammed by an enormous amount of messages like this
Simply stopping our application server, did stop spamming but we need that server running. We have rolled back all the latest code changes in the enterprise application, but it didn't solve the problem and didn't decrease the load on Security.evtx.
We have also checked that the infrastructure guys didn't reconfigure any settings on this server, especially auditing policy. (Last changes were 1 month ago).
Inspecting the process, we found that it constantly turning to registry \HKLM\SYSTEM\Services\EventLog\ and enumerates through all the keys below, they're around 800
Then we figured out that it's the auditing policy is configured in a way to log each of those reads to EventLog. Disabling the auditing policy solved the problem.
But the question is: How this could happen if nobody changed the auditing policy configuration? Windows didn't restart, no updates were installed lately. The only thing was changed - the latest version of an enterprise application was deployed, with no changes in logging or registry access.
Is this normal that such checking iterates through all registry keys below \HKLM\SYSTEM\Services\EventLog\ ? (Have to mention, this piece of code was there for ages)
