Since the early, innocent days of the Internet are now long past, everyone is concerned with computer security. With the prevalence of constant connections to the Internet via cable modems, ISDN and DSL lines, even private individuals have been confronted with the need for firewalls. Open source systems are the easiest to secure. This is not only because the code has been analyzed by many different people, including some security experts, but also because it is simple to change the code once a vulnerability has been found.