For the first time in nearly two years, the United States failed to cut the amount of spam originating from within its borders, according to Sophos' latest report on spam relaying countries, released today.
Although China was primed to become the top spam-producing country in the world at the end of this year's first quarter, the U.S. has hung on to the dubious distinction, producing 23 percent of the world's spam emails during the second quarter of this year.
China remained in second place, producing 20 percent of global spam, with South Korea a distant third with 7.5 percent of the world's spam production. France finished fourth, producing 5.2 percent of the world's spam, according to the report.
Spain, Poland, Brazil, Italy, Germany and the United Kingdom rounded out the top 10, each producing less than 5 percent of the world's unwanted email messages.
The vast majority of the world's spam is produced by zombie PCs, according to Sophos.
Gregg Mastoras, senior security analyst for Sophos, said today that despite the top ranking, the U.S. is working hard to halt the production of spam within its borders.
"I think the U.S. has done a pretty good job of decreasing the amount of spam coming out of the country, due to indictments of major spammers and police efforts," he said. "(Internet service providers) have stepped up, as has Microsoft in applying pressure. The U.S. is still the largest internet commerce country out there, and we've still got a little ways to go before we get this taken care of."
An April report from Sophos also determined that the U.S. produced 23 percent of the world's spam during the first quarter of this year, with China, including Hong Kong, producing nearly 22 percent and South Korea producing nearly 10 percent.
Asia remained the world's top spam-producing continent by far, creating 40 percent of the world's spam during this year's second quarter. Europe produced 27 percent and North America nearly 26 percent during that period.
Researchers at Sophos believe spammers in Russia, despite being absent from the "dirty dozen" list, are controlling vast networks of zombie PCs, according to a company news release.
The company also estimated that 15 percent of all spam emails are now part of pump-and-dump scams.
A study by CipherTrust released last month revealed that 64 percent of spam servers are based in Taiwan, with 23 percent in the U.S. and 3 percent in China.
That study also found a 21-percent increase in the number of new zombie PCs since May.