What is a good utility to block outbound traffic on the home network?
Ideally it will not need to be set in a browsers proxy setting to be
effective.
Cheap old PC, two nics, stick OS of choice on, create firewall rules,
install squid, setup, use this as your new default gateway, done. I
easily did this with OpenBSD, PF and Squid and it can be done in no
time at all. I never tried it with Debian but you can quite easily do
it with that. You would end up with something similar to;
Modem - > Gateway - > Switch - > Clients
Better, you buy a wireless that runs openwrt, install openwrt and do as
described above. Of course, you can also buy one of those atom based
ultra-low-power-usage boxes. This gives you more processing power than
an average wireless router, but that is usually not needed for a small
network.
Although the initial investment might be a bit higher, the lower power
consumption usually is worth it. Saving 50 watts (which is easily
attainable when migrating from a pc to a low-power unit) earns you
something like 80 euro/year (or 70 pound/year) and saves us some CO2
emission as a bonus. Do your math...