A stealth firewall is a bridge that applies firewall rules to packets that pass through it. The reason "stealth" is used is because a bridge is transparent to the machines using it: they can't tell that all the machines in the subnet aren't on the same physical lan. This also means that you can insert and remove such a device without disruption or indeed any awareness by the users of the network. The device itself doesn't even requre any ip addresses of its own, so it can be truly invisible.
These are also sometimes called "transparent firewalls", "in-line firewalls" and (of course) 'bridging firewalls".
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More Articles by Tony Lawrence © 2009-11-07 Tony Lawrence