!!! Overview
[{$pagename}] is a [Proxy] or [Gateway] [Network device] used for [security] that is an [Observer] and can perform [Monitoring] and may be able to controls incoming and outgoing [network traffic] based on predetermined [Access Control Policy] 


[{$pagename}] typically establishes a barrier between a [trusted|TrustedDomain] internal [network] and untrusted external [network] such as the [Internet].


[{$pagename}] are often categorized as either [Network] firewalls or [Host-based] [{$pagename}]. [Network] [{$pagename}] filter [network traffic] between two or more [networks] and run on [Network devices]. [Host-based] [{$pagename}] run on host computers and control network traffic in and out of those machines.

!! Many Types
There are many types variances within [{$pagename}]. Consult the references or "Google" to find more.

!! More Information
There might be more information for this subject on one of the following:
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* [#1] - [Firewall_(computing)|Wikipedia:Firewall_(computing)|target='_blank'] - based on information obtained 2018-03-23