You can track GPO links changes by analyzing the security eventlog, GPO links will give you information on which objects your GPO is applied to. We will monitor GPLink attribute changes.

In order to analyze in real time the security log of all your DCs you need to pay for a Syslog solution, like Snare or Kiwi. Or you can try to setup an eventlog forwarding solution if you are under Windows 2008, you can also try to run a script that catches security log events, but you might encounter some performance issues.
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