Hi Jeroen,
First of all, it's a transparent proxy so there's nothing like a proxy.pac or anything else for configuration. The proxy just sits there, listens and filters. Can be done with a variety of tools like squid, dansguardian and some more. The most advanced I know is the proxy combination Astaro uses at current. My installation is - by far - simpler.
Second, I'm not talking about users who know what they're doing. The users I host are in fact users who have absolutely no clue about what they're doing at all. Some of them even struggle with right-clicks and left-clicks. If they click, it's mostly the very well known "klick-you-should-not-have-done". It's challenging for them to use E-Mail. And it's even more challenging for them not to open up a message of a sender they don't know.
It's the sort of users AOL may be sending away because they think this kind of people should not be allowed to use electricity at all.
And, to make one thing clear: I'm not serving 1000s of users. I'm, in fact, serving about 10-20 users in the neighborhood. As I get all the calls when something goes wrong anyway I have choosen the proxy to get rid of those IE, FF & MSN viruses.
The virus-scanner included in the proxy is keeping out most of the stuff (and there's quite a lot according to the log-file).
For skype this is not yet possible. But for "my" users, they're not even using it with the exception of about two or three of them.
I absolutely agree with you that the solution I have is probably an (perhaps even excellent) solution for a problem that should never have existed in the first place.
CU tobias