Thankyou for your quick response. I have referred the above link which you shared.
In that post they have mentioned the below query to find the number of logins made to Splunk.
"index=_audit info=succeeded action="login attempt" | stats count by user"
This query is giving only the count of logins which are made by splunk users. It is good enough. But in addition to this, I need the login attempts made by other servers/databases also. For example, I have setup a forwarder in Host X. All the required log details from the host X is forwarded to my splunk instance and index over there. So while indexing also, my splunk is been accessed by the host/forwarder. I would like to have that information also.
How about the logs available in "sourcetype=WinEventLog:Security"? I have referred some posts, where people were discussing about the EventCode 4625 or 4624 (login success/failure).