Changes

A '''firewall''' is a system which filters network activity and permits presumably safe [[internet]]/intranet traffic while blocking suspicious or unwanted communication.<ref>“Definition of firewall in English by Oxford Dictionaries.” Oxford Dictionaries | English, Oxford Dictionaries, http://en.oxforddictionaries.com/definition/firewall. Accessed 6 Sept. 2017. </ref> There are several types of firewall and methods of filtering.

A '''firewall''' is a system which filters network activity and permits presumably safe [[internet]]/intranet traffic while blocking suspicious or unwanted communication.<ref>“Definition of firewall in English by Oxford Dictionaries.” Oxford Dictionaries | English, Oxford Dictionaries, http://en.oxforddictionaries.com/definition/firewall. Accessed 6 Sept. 2017. </ref> There are several types of firewall and methods of filtering.

===Hardware===

===Hardware===

Hardware firewalls are generally considered the best front-line of defense. When an incoming connection reaches the protected network, the connection must first go through this hardware firewall.  If the connection is unwanted, it will generally be ignored.  In this case, the entity attempting to connect will simply have their request time out.  Some firewalls will outright reject the request, however, which is a less effective defense method. (If rejected outright, a potential attacker will know he has found an active device, whereas if the request is ignored, it will be more difficult to know if there is even a device to connect to.)<br />

Hardware firewalls are generally considered the best front-line of defense. When an incoming connection reaches the protected network, the connection must first go through this hardware firewall.  If the connection is unwanted, it will generally be ignored.  In this case, the entity attempting to connect will simply have their request time out.  Some firewalls will outright reject the request, however, which is a less effective defense method. (If rejected outright, a potential attacker will know he has found an active device, whereas if the request is ignored, it will be more difficult to know if there is even a device to connect to.)<br />

To the outside world, there is only one device (the firewall) on the protected network. Even when a connection is permitted, the communication still passes through the firewall using a specified port.  Therefore, even active connections do not reveal the internal [[IP address]] of devices.<ref name="WhatIsMyIPAddress.com">“What is a Firewall?” WhatIsMyIPAddress.com, http://whatismyipaddress.com/firewall. Accessed 7 Sept. 2017.</ref><br />

To the outside world, there is only one device (the firewall) on the protected network. Even when a connection is permitted, the communication still passes through the firewall using a specified port.  Therefore, even active connections do not reveal the internal [[IP address]] of devices.<ref name="WhatIsMyIPAddress.com">“What is a Firewall?” WhatIsMyIPAddress.com, http://whatismyipaddress.com/firewall. Accessed 7 Sept. 2017.</ref><br />

However, many hardware firewalls (all but the newest types) often do not know what connections are being used for.  Most do not collect the packets and reassemble messages, so connections can be abused without the firewall knowing.  Even the ones which do attempt to analyze traffic can have difficulty understanding what is going on.<ref name="WhatIsMyIPAddress.com"/>

However, many hardware firewalls (all but the newest types) often do not know what connections are being used for.  Most do not collect the packets and reassemble messages, so connections can be abused without the firewall knowing.  Even the ones which do attempt to analyze traffic can have difficulty understanding what is going on.<ref name="WhatIsMyIPAddress.com"/>

===Software===

===Software===