Linux: 20 Iptables Examples For New SysAdmins. Linux comes with a host based firewall called Netfilter.
According to the official project site: netfilter is a set of hooks inside the Linux kernel that allows kernel modules to register callback functions with the network stack. A registered callback function is then called back for every packet that traverses the respective hook within the network stack. The Original Magazine of the Linux Community. Linux Today - Linux News On Internet Time.