During the first quarter of 2012, 20 percent of spam e-mails were sent from India. The study was conducted by security software firm Trend Micro.

The firm said attacks are ongoing, long-term attempts, rather than the short-term attempts scammers have typically been known for.

"The quarter's top spam-sending countries included India at 20%, Indonesia at 13%, South Korea at 12% and Russia at 10%," the firm said.

The firm also said the number of attacks has "dramatically increased." "Unlike largely indiscriminate attacks that focus on stealing credit card and banking information associated with cybercrime, targeted attacks noticeably differ and are better characterised as 'cyber espionage," the firm added.

Google's Android operating system is also a target, due to its growth, with the Q1 report identifying about 5,000 new malicious apps on the mobile OS. "With the increased use of smartphones for Internet access and the huge Android user base, the increase in attacks targeting the platform is thus not surprising," the firm said.

But Android isn't the most vulnerable OS: that's Apple's iOS, despite being considered the safest mobile operating system due to the closed ecosystem versus Android's open source software.

"Apple surpassed Oracle, Google and Microsoft in reported vulnerabilities, with a total of 91. Oracle came in second, with 78; Google, 73; and Microsoft, 43," Trend Micro said. Apple also saw the outbreak of Flashback Trojan which infected 600,000 computers. Recent estimates say 140,000 Macs remained infected despite Apple tackling the problem.

Research from U.S.-based IT security and data protection firm Sophos also said India has overtaken the United States as the top global contributor of junk message, responsible for one in 10 spam e-mails. Its report was also published in the Q1 2012.

India's rise comes as the number of Internet users has increased, which broke 100 million by the end of 2011 and continues to grow.

Computers in India are not properly protected, the firm said, and Internet Service Providers are "not taking spam seriously."

The UK was in sixth place in the table last year, accounting for 3.2 percent of global spam, and has since fallen off the top 12 list. UK spam has also decreased by 47 percent.

(reported by Jonathan Charles, edited by Dave Clark)