You can do this by using an external lookup script that gets the corresponding IP address from the DNS entry. There's a script that's included with Splunk as an example that does just this. More information is available here: http://docs.splunk.com/Documentation/Splunk/latest/Knowledge/Addfieldsfromexternaldatasources
The telnet session will occur between two CPU. So isn't there an option of having IPs of both machines rather than have the name. Since identification process would far more easier and less time consuming.
for eg. There is a telnet session which takes place between two PCs in the network. Rather than having a hostname=CPU-WS2 representing that session. Is there an possibility that an IP could there instead ?
Message=A process has exited:
Image File Name:C:\WINDOWS\system32\telnet.exe