You can set the Internet Explorer Proxy settings via Group Policy. There are two methods in which you may want to set proxy settings
Contents
Create a Group
Group Policy Extensions (KB943729)
Per Computer
Per User
Disabling Internet Access
Using the techniques described above you can effectively disable internet access for a targeted group of users and/or computers. All you have to do is set the proxy server to 127.0.0.1 which sets the local device as the proxy server and thus prevents URL's from resolving correctly.
Warnings
The process outlined above does not prevent users from accessing websites via IP address. If you require this sort of thing a dedicated proxy server such as [Squid] would be more appropriate.
Reference
http://www.smart-x.com/?categoryid=171&articleid=149 http://www.tomshardware.com/forum/221139-46-make-proxy-settings-machine-rather-user http://community.spiceworks.com/topic/33803