More email spam originated from India during the first three months of 2012 than from the US, making the south Asian country the world's leading spam source.

Security firm Sophos said that India was responsible for 9.3% of global email spam traffic seen from January to March, according to their latest Dirty Dozen report, which lists the top 12 countries from which most spam originates.

The US, which has been the traditional leader of the list, came in second place after India during the first quarter of 2012, with 8.3%. It was followed by South Korea with 5.7%.

The vast majority of spam is sent by computers that have been infected with some type of malware and are now part of a botnet, Graham Cluley, a senior technology consultant at Sophos, said. "If you have a spam in your inbox, there's an almost one in 10 chance that it was relayed from an Indian computer."

India's new position as king of spam among countries was also confirmed by spam reports from other security vendors. The monthly spam statistics published by antivirus firm Kaspersky Lab for January, February and March also listed India as the top spam source.

However, the US didn't even make it into Kaspersky's top 12 spam sources for these three months, so there is definitely a discrepancy between what the two antivirus vendors are seeing.

The overall throughput of global email spam messages has decreased during the first three months of 2012 compared to the same period in 2011. This is because of antispam actions taken by ISPs, but also because spammers have started favouring social networks for marketing spam, Cluley said.

However, malicious spam, which includes phishing and messages that lead to malware, continues to be heavily distributed via email and has actually seen an increase.

"Don't allow your computer to be a contributor to the global spam problem," Cluley wrote. "Defend it with up-to-date anti-virus software, and take care over the links that you click on and the software you install."