The United States is still the world's largest spam generator, but other countries are catching up fast.
Since the start of the year over 35 per cent of the world's spam has come from computers inside the US, according to figures from security specialists Sophos.
South Korea is in second place with nearly 25 per cent and the UK is ranked ninth at 1.6 per cent.
"Although the USA is responsible for producing more than a third of all of the world's spam, its percentage contribution has decreased," said Graham Cluley, senior technology consultant for Sophos.
"The percentage of spam sent from American computers has fallen 12% since the start of the year compared to other countries."
"ISPs enforcing policies to ensure they do not knowingly provide network services to spammers, and a rising awareness of the need to protect all computers from being hacked by spammers has undoubtedly contributed to this trend."
The company has also warned that over half of all spam is sent by ?zombie? PCs; computers that have been infected with Trojan software that allows spammers to use home PC systems to generate spam.
Spam now regularly accounts for more than 90 per cent of all emails in circulation.
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