How to Lock Down A Computer?

[Computer Head]

Why don't you also have a router with a strict only allow certain IP addresses rule?

These IP addresses would be yoru primary and secondary DNS server as well as your comapny website. Any other traffic would be BLOCKED.

That's a great way to minimalize traffic. It will only give you access to one site. Have to make sure that it is on a detached network, so other computers don't undesirably get restricted.