After you've implemented your selectively slow proxy with HTTP::Proxy you will want to think about how to force all users to use your proxy.
This will come down to your default gateway selectively re-routing all internet traffic to port 80 to your proxy. Consider linux and iptables.
Actually, if you want to get smart, you could instead configure iptables to drop every nth packet to particular destinations; this would cause clients' TCP steams to severely slow down (but not altogether break). Performing selective packet drops like this will have an effect on even those attempting to bypass your custom proxy using HTTPS or SSH :) |