If you have your own MTA running... you are probably known with the spam-problems... Once you've tuned the filters, you have to do it again... because a new spam-run comes in. I also blocked whole /8 subnets in different countries (India/China/...)... but that is not a "real" solution... aka I want to block the whole country...
The "DNSBL" countries.nerd.dk allows you to do so... the map ip-adresses to countries based on whois-information... so on my MTAs I added the following lines to the mc sendmail file:
FEATURE(dnsbl,`br.countries.nerd.dk', `554 - Rejected - SPAM from Brazil:$&{client_addr} rejected')dnl
FEATURE(dnsbl,`in.countries.nerd.dk', `554 - Rejected - SPAM from India:$&{client_addr} rejected')dnl
FEATURE(dnsbl,`kr.countries.nerd.dk', `554 - Rejected - SPAM from Korea:$&{client_addr} rejected')dnl
FEATURE(dnsbl,`cn.countries.nerd.dk', `554 - Rejected - SPAM from China:$&{client_addr} rejected')dnl
FEATURE(dnsbl,`ro.countries.nerd.dk', `554 - Rejected - SPAM from Romenia:$&{client_addr} rejected')dnl
FEATURE(dnsbl,`co.countries.nerd.dk', `554 - Rejected - SPAM from Colombia:$&{client_addr} rejected')dnl
FEATURE(dnsbl,`mk.countries.nerd.dk', `554 - Rejected - SPAM from Macedonia:$&{client_addr} rejected')dnl
FEATURE(dnsbl,`vn.countries.nerd.dk', `554 - Rejected - SPAM from Vietnam:$&{client_addr} rejected')dnl
FEATURE(dnsbl,`ru.countries.nerd.dk', `554 - Rejected - SPAM from Russia:$&{client_addr} rejected')dnl
And within a few hours the first are already blocked... I hope this will reduce the amount of incomming spam at the "front door". Because simply... I don't know people in these countries...
