Interesting information from ISCALabs:
Though the top four positions remained the same last week compared to the week before, Brazil continues to slowly account for a larger percentage of the spam pie. Russia and the United States had larger than usual gains (up 1.2% and 1.4% respectively) according to data collected by ICSA Labs. The increase for the United States was enough to move that country into the 5th position among the Top 10 Countries Sending Spam. See who else rounds out the top 10. Also see the graphrepresenting spam percentages over the last several months for many of the top spam sending nations.