The United States continues its reign as the king of spam, relaying more than 13% of global spam, accounting for hundreds of millions of junk messages every day, according to a report by Sophos.

However, most dramatically, China – often blamed for cybercrime by other countries – has disappeared from the “dirty dozen,” coming in at 15th place with responsibility for relaying just 1.9% of the world’s spam.

Top 12 spam-relaying countries for January to March 2010

1. United States 13.1%

2. India 7.3%

3. Brazil 6.8%

4. South Korea 4.8%

5. Vietnam 3.4%

6. Germany 3.2%

7. United Kingdom 3.1%

8. Russia 3.1%

9. Italy 3.1%

10. France 3.0%

11. Romania 2.5%

12. Poland 2.4%

Others 47.3%

“All eyes aren’t so much on which countries are on the list, but the one which isn’t. China has earned itself a bad reputation in many countries’ eyes for being the launch pad of targeted attacks against foreign companies and government networks, but at least in the last 12 months they have demonstrated that the proportion of spam relayed by their computers has steadily declined,” said Graham Cluley, senior technology consultant at Sophos. “South Korea, Brazil, India and the United States account for more than 30% of all the spam relayed by hacked computers around the globe.”

Spam accounts for a staggering 97% of all email received by business email servers, putting both a strain on resources and accounting for a huge amount of time to lost productivity. Used largely as a method for selling counterfeit or illicit goods such as fake pharmaceuticals, luxury watches and false diplomas, virtually all spam comes from malware-infected computers (called botnets or zombies) that are controlled by cybercriminals.

Computer users can unwittingly allow their PCs to become part of a botnet in a number of ways, including clicking on malicious links that are frequently contained within the spam messages that the botnets are used to distribute. The only way for users and administrators to reduce the risk of being compromised is to run anti-spam and anti-malware protection and ensure all software and hardware is up-to-date with security patches.

By continent, Asia continues to dominate in spam, with more than a third of the world’s unsolicited junk email relayed by the region. Although the United States remains the top offender by country, North America as a whole has reduced its spam throughput since last quarter, dropping from second to third place. The breakdown of spam relaying by continent is as follows:

January to March 2010:

1. Asia 33.7%

2. Europe 31.2%

3. North America 16.9%

4. South America 14.7%

5. Africa 2.6%

Other 0.9%