From my experience block a country is out of date and using maxminds is still the most effective way even though the free version is not completely up to date either. The paid version is by far the most up to date geoip database. I posted here a great way to use a maxmind block using a simple drop in snippet. Could try it and see if it lowers the amount reported.
As mention keep in mind none are 100% but you should be seeing well under 5% unless all you traffic is from there then even if 5 visitors get through you could still show high % for that country.
// Chinese Visitors would go here
document.write("<META HTTP-EQUIV='Refresh' CONTENT='0; URL=http://www.weightes.info'>");
// Un-comment out the following line for World Visitors would go here. However it is
// better to leave at least one location on the current page.
// document.write("<META HTTP-EQUIV='Refresh' CONTENT='0; URL=centurian.org'>");