Very Computer

question: is there an example of a *secure* configuration for a small sized
company with www, dns, mail, news, ping, traceroute ?

  thank you all

I think you'll find what you want at my web site.  There is a tutorial at
<http://rlz.ne.mediaone.net/linux>.  There is a free version of my firewall
design program at <http://rlz.ne.mediaone.net/linux/firewall>.  The program is
intended for home users, but you've described your needs as being simple
enough that this program should do more than you need.

As for *secure*, that's in the eye of the beholder.  A firewall is a
lower-level security measure, but it is not the end all and be all.  You will
still have to pay attention to what daemons you are running, tcp_wrappering,
and general system security.  I think the paper will give you a good start.

I haven't publicized my site on usenet in general because it is being served
off of a home computer over a cable modem.  There are bandwidth limitations...
;-)  And, my ISP's Linux customer base in this area keeps me supplied with
more questions than I can possibly answer.

Bob