Block website without forcing user to restart browser?

Question

I know blocking a website is a popular question but none of the answers I've seen address my particular situation:

I want to block a website (to be selected by the user, which must also have Admin rights, on Windows XP), without forcing her to restart her browser.

The well known technique of modifying the hosts file requires some browsers to be restarted. I want to accomplish that in a way that is browser-independent (e.g. Content Advisor works in IE but not in FF) and which doesn't require the user to restart his browser.

Please note that I am interested in knowing how to do this programmatically, so http://superuser.com or http://serverfault.com aren't really the right places for this question, as they mostly suggest tools and services, while I am interested in the underlying knowledge so that I can implement it myself.

Ideas?

Thanks.

Answer 1

Please note that I am interested in knowing how to do this programmatically, so http://superuser.com or http://serverfault.com aren't really the right places for this question, as they mostly suggest tools and services, while I am interested in the underlying knowledge so that I can implement it myself.

Such tools would filter traffic by implementing a NDIS Intermediate Driver. See also this other question.