> There are a number of things that are easy to block, such as web
> traffic, smtp traffic, web traffic to a particular IP address or
> network, most IRC servers and so on.  There are a number of things
that
> are much harder to block, such as MSN Messenger, Kazaa, Yahoo!
> Messenger, and so on.

I'm not an expert in this area, but...

Wouldn't MSN Messenger and YIM etc. connect with one (or a limited
number of) server(s), which could then be blocked using some
source/destination rules.

Kazaa clients would be a problem, but again the server should be
block'able in much the same way.

... Or am I missing something?


A-)