In today’s dangerous cyberworld, it is mandatory to have some defense measures against either intentional or unintentional attacks. Firewalls allow us to block or allow traffic into our computer or network, based on different criteria, such as IP address, port range, etc.
In a large network, the admin usually defines several “zones ,” that is, groups of computers with similar security requirements. For example, if we have a web server and an FTP server that are available from the Internet, these computers require far more protection than an FTP server that is only accessible by local users. ...
