A lot of next gen firewalls have the ability to tag web browsing with a user associated to the computer it came from. I'm going to show you how to change who the firewall thinks you are for Palo Alto User-ID, and likely other devices.
Palo Alto uses a secondary software package called User-ID Agent. This software monitors the event log on domain controllers and pulls the username associated with a computer from the event log. So when you logon an event is registered with the domain controller, User-ID Agent pulls the info and updates it's data with who is logged in.
If you do a runas /user:domain\user (must have the actual credentials) and start any application, that will register on the domain controller as a new logon to that computer and will adjust the user appropriately. It does not change back or register as "no user" if there is a logoff, only logons change it. So from that point on all traffic is associated with a different user, still your IP address but it says "User x was logged into the computer at this time".
Palo Alto can do traffic filtering by user id, so if you knew the login for an account that is unrestricted, as far as the firewall rules are concerned, you could login as yourself, do a runas and start a cmd prompt (or whatever) then close it and all your traffic will be reported as belonging to the other user possibly bypassing rules setup to block other users traffic.
Or you could hang some co-worker as you went to some horrific granny-tranny spanish-mistress bondage porn site and it got registered in the firewall logs and now HR and IT will be grilling some poor soul about their internet browsing habits.
Things such as opening outlook will revert back to being reported as your user is logged into the computer as it authenticates to AD. Anything that authenticates to AD will create a logon event and will change the user reported as logged on to the computer.