Moving around firewalls

Firewalls come in several different flavors. Software- and hardware-based systems are designed to work with different network setups. If you are running a business, for example, your firewall unit will be entirely internal. This means that everything is locked down on one side of the computer's firewall, and everything outside of the network is locked down on the other side. Your firewall will also block all communication between users of your LAN. They do this by locking down your IP addresses so that only certain users can access certain sites based on the specific rules you have established.

Bastion host

These are designed to protect services on other machines and are often used to protect databases. Each time a request comes in, the bastion host checks whether it knows how to communicate with that service (and will allow that service to share back), then passes the request on.

Screened subnet (or demilitarized zone (DMZ))

These are used...