This site provides information and programs relevant to security of systems. Anyway, don't forget that the work of so-called hackers exclusively bases on inattention of system-makers and on software bugs arising from servers and from operative systems. If a system-maker takes precautions such as to disable not necessary services, to set access-passwords with more than 10 digits that will be changed at least every month, to install HOTFIX and SERVICE PACKS...then the work of the hacker will be consequently hard if not impossible.
Remember that a sniffing aiming at analysing all the packets going along a network segment has to be carried out by means of programs installed on systems connected with the same segment : the result is that if the hacker can't enter these systems, the installation of these softwares will be impossible such as the same sniffing. Softwares like CARNIVORE need installation on systems that have to be supervised.
This means that by taking care of your operative system, you'll make hard the life of those who abusively enter your computers.
On the contrary, use yourself sniffing programs on your systems in such a way as to get knowledge about not authorized use of certain services or of certain IP.
Programs like CommView or Anasil II show all your network use and you'll understand if something is going wrong. On a professional network devote a system to the evaluation of the network traffic by means of several packet-analysers and by means of softwares in order to identfy probable intrusions. Another secret is to use servers on intranet addresses re-addressing public IP toward private IP through a software as RINETD.
In such a way you'll carry out a bridge between public and private IP only as regards requested services in order to avoid hackers' entrance on meaningful systems.
Moreover, "lark-mirrors" are excellent ways to congregate hackers' efforts onto sofwares that carry out no service but simulate to do.
For example, I've disabled TELNET on a system but there's a program that opens a socket on TELNET's door in order to simulate that this service is still running. Infact, this program only simulates a prompt and nothing more...neither checks the login but, on the contrary, warns about a wrong attempt. All the possible exploits have no effect on a well-protected system.
Another precaution is a choice of a very good firewall.
For professional services do not use firewalls in software but trust to firewalls like CISCO PIX 515 or similar ones that can carry out rules on packets and will perform tests on fragmentary characters and on other kinds of abuses of TCP and IP protocols.
To be sure to be informed about all HOTFIX and about all service packs, send a message without subject and without text to : microsoft_security-subscribe-request@announce.microsoft.com
I hope to keep on bringing up-to-date my site in English.

Napolifirewall.com ;=)