There are software that can help you to do that, you can find it searching in google for example. To install an IP filter you need to define one or more IP groups, for example ranges of IP numbers that can be named and labelled according to their meaning. You can do this by SiteAnalisys Administrators on the setup section.
I would try to make more money on the browsing papers (ie pop unders) since you can not use google on the proxified pages. But the site looks clean