Splunk is _not_ an active monitoring solution. That's what you use - for example - rancid or some commercial tools for. But if you get logs from such tool (or have audit logs from your appliances telling you that change happened), you can search from that data. But it will depend on what data you have.
It's the query to search those logs that I am looking for.
The "query" (or in Splunk terminology - search) you're looking for will depend on what data you have indexed in your Splunk.