SophosLabs, a well-known network of threat analysis centres, currently held the Dirty Dozen Spampionship to find out so called 'spam-relying' countries guilty of sending a great majority of email spam worldwide. For three months (from April to June, 2014), the company has been keeping track of locations of computers that sent junk messages all over the globe.
The overall result suggested the United States of America for being at head of the Dirty Dozen by pure volume. The USA seem to provide about 24.2% of all spam email, thus leaving their main competitors France (6.7%) and China (6.2%) far behind.