The U.S. produced nearly a quarter of the world's spam emails in the first three months of 2006, sending 23 percent of the world's spam.
China, including former British protectorate Hong Kong, was responsible for 21.9 percent of the world's spam during that same period. South Korea finished a distant third, producing 9.8 percent from January to March.
The new statistics show the U.S. has made considerable progress fighting spam in recent years, indicating that the CAN-SPAM Act, state laws, information sharing by internet service providers (ISPs) and jail time for spammers are working.
Last October, the U.S. accounted for more than 26 percent of the world's spam, then a huge drop from the year before when the U.S. was accountable for 41.5 percent of global spam.
Graham Cluley, senior technology consultant for Sophos, said more PC users are now aware of spam's dangers.
"Two years ago, the U.S. accounted for over half of all spam sent to the world – now it is less than a quarter, evidence that confirms that more Americans are waking up to the need to protect their home computers from malicious hackers," he said. "More and more viruses, worms and trojan horses are being designed to take over innocent users' computers with the intention of stealing information and sending out junk email campaigns."
The drop in U.S. spam was also evident in the percentage of spam North America produces as a whole.
Asia continued to lead the world in spam production, with nearly 43 percent of all production. North America distributed 25.6 percent, just beating out Europe, which produced an even 25 percent. South America was far behind in fourth place with just over five percent.