jmccormac - 12:54 pm on Aug 30, 2013 (gmt 0) [edited by: jmccormac at 1:27 pm (utc) on Aug 30, 2013]
That approach (starting with A ranges) might be ok for country level blocks but sorting genuine human users from data centres and hosting ranges might require a bit more precision. Blocking at the upstream provider IP range might deal with server farms. Those CN/IN subnets are a common thing. Where a country's internet infrastructure isn't well developed a high percentage (possibly 50% or more) of that country's websites might be hosted on IP ranges outside that country. The US, CA, DE and UK tend to be the most popular. Using an A approach is, perhaps, like using a chainsaw when a scalpel is required. That said, I do have a few countries blocked on some of my sites.
You could reduce those numbers by leaps and bounds with a few lines of mod_rewrite
[edited by: jmccormac at 1:27 pm (utc) on Aug 30, 2013]