TeamCity identity question

I'm using T/C on a Windows build server.
I feel like I should know this, but can someone tell me how to find the Windows Identity being used by T/C?

I'm trying to deploy to a web server, but can't access the path, access denied.

I know this is due to that the web server folder is locked down, and won't allow Team City permission to write to it.  But in order to fix it, I need to know what identity T/C is using.