The dubious honour goes to the United States of America.
According to a report of the security firm Sophos more than two of every five messages originate from the US. In percentage terms, it means that a whopping 42.53 per cent of spam orignates from the US.
The study also throws up a surprise with the next largest source being South Korea, with 15.42 per cent. China and Hong Kong account for a combined 11.62 per cent.
The report released on Tuesday suggested that a US law known as CAN-SPAM that took effect in January has done little to curb the flood on unwanted messages that some seen as a threat to the Internet.
Chris Kraft, senior security analyst at Sophos, said the results showed little overall change from a similar survey in February for the United States.
"Six months and millions of spam messages later, it is quite evident that the CAN-SPAM legislation has made very little headway in damming the flood of spam," he said. "If nine months isn't long enough to make a significant difference, how long is?"
The 'dirty dozen' spam sources, according to Sophos, included Brazil, accounting for 6.17 per cent of global spam, followed by Canada (2.19 per cent); Japan (2.87 per cent); Germany (1.28 per cent); France (1.24 per cent); Spain (1.16 per cent), Britain (1.15 per cent); Mexico (0.98 per cent); and Taiwan (0.91 per cent).