This month and next month, I'm going to take a look at filtering packets with iptables, the replacement for ipchains in the 2.4 Linux kernel. This month, I will deal with the basics of getting iptables up and running, and next month I'll explore using iptables in detail. The iptables modules can handle filtering and management of incoming and outgoing IP packets. The iptables module is part of the Netfilter framework in the 2.4 Linux kernel. Some references to iptables that I've seen in other articles are a bit confusing, because they seem to refer to Netfilter and iptables as the same thing. Netfilter is actually a series of "hooks" in the network protocol stacks that allow modules to work with network packets. At certain points in a packet's travel through the protocol stack, the Netfilter framework can allow a module to forward or drop a packet, change it in some way, queue it for a user-space (non-kernel) program or simply let it go on its way.
News: Firewalls
