However, Europe now has six entries in the dirty dozen, which when combined, account for even more spam-relaying than the US. Sophos notes that the number of compromised PCs continues to rise steadily in Europe.

According to Sophos, the overall global volume of spam rose by around 9 percent during Q2 2007, when compared to the same period in 2006.

The top twelve spam-relaying countries are as follows:

1. United States - 19.6%
2. China (including Hong Kong) - 8.4%
3. South Korea - 6.5%
4. Poland - 4.8%
5. Germany - 4.2%
6. Brazil - 4.1%
7. France - 3.3%
8. Russia - 3.1%
9. Turkey - 2.9
10. United Kingdom - 2.8%
10=. Italy - 2.8%
12. India - 2.5%
Others - 35.0%

"While the US remains top spam dog, the latest chart emphasises the urgent need for joined-up global action to combat this growing problem," said Carole Theriault, senior security consultant at Sophos. "For every spam campaign, the spammers, the compromised computers used, and the people being deluged by the unsolicited mail are often located in totally different parts of the world. A consolidated effort is needed not only to pursue and prosecute spammers, but also to convince computer users everywhere of the importance of blocking rather than responding to spam messages. Everyone has a part to play if we are to win the global battle against spam."

According to Sophos, the growing number of PCs across the US and Europe, combined with an increase in the amount of internet service providers offering cheap internet access - not all of which have taken adequate steps to prevent spam-relaying activity - are responsible for the strong Euro-American presence in the dirty dozen.