The United States continues to be the top country for spam, accounting for 15.2 percent of all global spam, an increase from 13.1 percent in the first quarter of 2010, according to a new report by Sophos.

India trails the U.S., accounting for 7.7 percent of worldwide spam, followed by Brazil (5.5%), the UK (4.6%) and South Korea (4.2%).

"It's sad to see spam relayed via compromised European computers on the rise - the UK, France, Italy and Poland have all crept up the rankings since the start of the year," said Graham Cluley, senior technology consultant at Sophos.

"Financially-motivated criminals are controlling compromised zombie computers to not just launch spam campaigns, but also steal identity and bank account information. It's an uphill struggle educating users about the dangers of clicking on links or attachments in spam mails, and that their computers may already be under the control of cybercriminals."

Europe has become the top spam-relaying continent, accounting for 35 percent of all spam, edging out Asia with 30.9 percent. North America and South America are responsible for 18.9 percent and 11.5 percent of spam respectively, while Africa accounts for 2.5 percent.

"Spam will continue to be a global problem for as long as it makes money for the spammers. It makes commercial sense for the criminals to continue if even a tiny proportion of recipients clicks on the links," explained Cluley.

"Too many computer users are risking a malware infection that sees their computer recruited into a spam botnet. To combat the spammers, it's not only essential for computer users to run up-to-date security software, they must also resist the urge to purchase products advertised by spam."