A way of accessing the name of the currently logged in user in a search? I'm pretty sure there's currently no straightforward way of doing that. What you COULD do is write your own custom command which gets the username from the session token, and then returns it so you can use it in your search. Have a look at southeringtonp's answer discussing the details of this in the following question: http://splunk-base.splunk.com/answers/23504/determine-currently-logged-in-username
You have your csv file, you have a field with the UserAccount that shows...something (logged in user on 220.127.116.11 at the time of attack? User that created this CSV report?) but you want to show UserAccount in some other way. Please give us more details on this one.