Feather Linux for firewalls
The firewall infrastructure of GNU/Linux consists of two parts, the kernel (netfilter) and the configuration structure (iptables). In order to build a firewall structure in GNU/Linux, you first need the proper netfilter support, which almost every Linux distribution includes by default. The second part is the set of rules that govern the packets (traffic) to be let in and the packets to deny.
These rule sets are called chains. To set your rules, you must set up a chain of them to manipulate packets appropriately.
By KIVILCIM Hindistan at O'Reilly.
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