Blocking a country (mass iP Ranges), best practice for the actual block

What we've found best is using the MaxMinds database at sign-up time. The free version locks down to country, and you can pay for more granularity.

The advantage of only doing it at signup time is that you're not going to make life awkward for customers who've already signed up who're travelling.

as far as I understand, the question is not where to get the list of ip addresses that need to be blocked, but rather how to block them with iptables efficiently. A script that does series of "iptables -A" commands is going to take very long time to load rules and during this time firewall runs with inconsistent policy. This has significant impact on its performance, too.

I suggest you try module ipset ( http://ipset.netfilter.org/ ) . It allows you to manipulate tables of address blocks directly, you only need one iptables rule to match the whole set. You'll need to experiment with different types of sets to find the one that can accommodate the number of ip address blocks you need to block and give you performance you need. In any case it is much better at matching long lists of address blocks and allows you to reload it using command line tool without touching the rules.

Note that not all Linux distributions include ipsets in their default configuration so you may need to recompile kernel modules and iptables.

Country address blocks change from time to time so you'll need to update your address set periodically. To reload the set that is already being used you can use command line tool "ipset" and it is easy to wrap it in a shell script to automate the process. Or you could use fwbuilder to generate your iptables policy and use the script it generates to manage ipset as well ( http://www.fwbuilder.org/4.0/docs/users_guide/address-table-object.html , see "5.2.13.1. Using Address Tables Objects with iptables IP sets" in this chapter)