NOTE: The DNSBL appears to no longer be working.
I recently discovered a wonderful DNSBL service reporting you where public Internet IPs are from.
The service is countries.nerd.dk: http://countries.nerd.dk/more.html
You can for example block any mail at your mailserver coming from china or russia, simply integrating this DNSBL with your MTA.
You can even get the country of your IP with dig!
Warning: You need to swap IP octets. If for example the IP to check is 192.162.132.171, you have to call 171.132.162.192.zz.countries.nerd.dk.
root@nbvirtdns1:/# dig TXT 201.65.24.151.zz.countries.nerd.dk
…
201.65.24.151.zz.countries.nerd.dk. 1047 IN TXT “it”
…
Una risposta a “DNSBL GeoIP service at countries.nerd.dk”
To block a country from sending mail to your MTA, you’d simply prepend the IANA country code to .countries.nerd.dk.
Examples:
cn.countries.nerd.dk -> China
kr.countries.nerd.dk -> Korea
pl.countries.nerd.dk -> Poland
ru.countries.nerd.dk -> Russia
br.countries.nerd.dk -> Brazil
ar.countries.nerd.dk -> Argentina