Installing a Firewall

Another way to protect your network is to use a firewall or secure gateway system. A firewall is a dedicated system separating two networks, each of which approaches the other as untrusted. You should consider this setup as mandatory between your internal network and any external networks, such as the Internet, with which you want internal network users to communicate.

A firewall can also be useful between some internal networks. For example, the firewall or secure gateway computer will not send a packet between two networks unless the gateway computer is the origin or the destination address of the packet. A firewall should also be set up to forward packets for particular protocols only. For example, you can allow packets for transferring mail, but not those for telnet or rlogin. The ASET utility, when run at high security, disables the forwarding of Internet Protocol (IP) packets.