Hi,
It's a funny way of doing it, but here it is.
Assuming you have control of the DNS server your users are using, usually
obtained by DHCP, you can setup an empty authoritative zone for
kazaa.com so
that it resolves to nothing, done, won't even bother your firewall.
Yang
This reminds me of a site that tells people to modify their hosts and
HOSTS files on linux/windows boxes for all the different
cookie/advertising sites as well. Blocking access to all the tracking
and downloads for advertising. Saves on bandwidth as well as speeds
up browsing.
Mike Skallas' Ad Blocking Hosts file