Back in 1998, I noticed aggressive ipv4 traffic coming from several countries within that ipv4 space. it was not necessarily the countries, but the country of origin for that ipv4 space.

 

Countries of threat were: Amsterdam, Australia, Japan, and China

 

The morale of the story is block those countries ipv4 space en masse. easy peazy lemon squeezy.

 

fast forward to 2005. the space is still a problem

fast forward to 2010. the space is still a problem

fast forward to 2015. the space is still a problem

 

now the space is more interesting...

 

more to come.