I've been working as the IT guy for a small printing company for a while, and I need to setup a proxy server, as it seems like the best way log internet activity, among other things.
What is the best way to go about starting this?
I want the users to be authenticated before getting access to the internet, and I want to make sure everything is logged (internal and external IP and port, TCP/UDP, authenticated username, etc.).

I'm not sure where the best place to start is. We're using a Windows domain, so I'm not sure if this is a job for Windows to authenticate users with their domain usernames, or if I can use Linux to do this. I'm also not sure where on the network a proxy server should be, whether it needs to be physically in between the firewall and the rest of the network or not.

Thanks in advance!