Sophos checked all spam messages it received over two days in February and came up with its 'dirty dozen,' the countries hosting the most prolific spam senders.
After the US, with 56.7%, is Canada – a long way behind with 6.8%. China and Hong Kong follow at 6.2%, then South Korea at 5.8%, the Netherlands at 2.1% and Brazil at 2%.
Germany, France, the UK (1.3%), Australia, Mexico and Spain make up the remainder of the dozen. The rest of the world accounts for only 12.2% of spam.
The figures may be misleading, however. According to Graham Cluley, senior technology consultant at Sophos:
"Our intelligence suggests that a large amount of spam originates in Russia, even though it appears at only number 28 in the chart. Hackers appear to be breaking into computers in other countries and sending out spam via 'infected' PCs."
"Some Trojan horses and worms allow spammers to take over third-party computers belonging to innocent parties, and use them for sending spam. More than 30% of the world's spam is sent from these compromised computers, underlining the need for a co-ordinated approach to spam and viruses."