I assume you're speaking of data volume, etc.
You'll be interested in the DMC: http://docs.splunk.com/Documentation/Splunk/6.2.0/Admin/ConfiguretheMonitoringConsole
You'll also be interested in SOS: https://splunkbase.splunk.com/app/748/
You'll also be interested in : index=_internal metric
Actually I need to monitor the log flowing from the internet (like DOS/DDOS attack).
Is this what you're looking for?
Thanks for your response! Actually what I need is that have to monitor the log flowing from the internet (like DOS/DDOS attack) to the remote host.