I used to block the sites by adding them to the HOSTS file, set to 127.0.0.1
A tiny webserver sent a realistic sympathetic error message whenever someone wanted a page from 127.0.0.1
Now I have another PC set up, which I'm fine with accessing them. Unfortunately, if I leave them in HOSTS, the proxy - AnalogX's simple Proxy - can't find them. And if I take them out, L12 (and his more annoying friends) can visit them from this PC.
It occurs to me that I could have two proxy servers on this PC. One would be set up to block listed sites, for local use, and the other - the one currently there - would let the other PC see them.
But which proxy to use? Free, small and fast, please. I'm not fussed if it does caching etc.
Or is there another way? It must work with both Firefox and IE, so a Firefox extension that blocks sites is no good.