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|{{Admon/note | | '''[http://en.wikipedia.org/wiki/Iptables Iptables] is the built-in firewall for LINUX'''. Iptables is a '''list of rules'''. Each rule is placed into a particular chain and when data is sent '''into''', '''out of''' or '''through''' a PC the data .If a rule is matched, it must “jump” to a '''condition'''. Simple conditions include '''ACCEPT''', '''DROP''' and '''LOG''' but there are also more complex conditions that can be applied and there is even the option to create your own conditions.

If a packet matches a specified rule, it must “jump” to an existing '''condition'''. Simple conditions include '''ACCEPT''', '''DROP''' and '''LOG''' but there are also more complex conditions that can be applied and there is even the option to create your own conditions. When using iptables, the '''Filter''' table is important; because it contains these the following essential '''three chains''':