Making the assumption that you are referring to the IP addys of the machines on your network you should be ok. If your firewall is properly configured at the router then that *should* be all that most people can see (if they can even see that). Just remember that this IS the internet we are talking about....to some, nothing is sacred and nothing is secure.

If you are feeling particularly paranoid, put a software firewall on each of your machines....you can never be TOO careful.