The US is still the top spam-relaying country, but its share of the global bane continues to drop, security vendor Sophos has reported in its latest statistics.

The US now accounts for 23.1 percent of spam sent, down from 24.5 percent only two months ago. Two years ago, the US accounted for more than half of all relayed spam, the company said.

China is still is second place with 21.9 percent, and it looks as if the country will overtake the US some time this year to claim the top spot. Other top places in what Sophos has termed the “dirty dozen” are occupied by, successively, South Korea (9.8 percent), France (4.3 percent), Poland (3.8 percent), and Spain (3.3 percent).

The UK is now in tenth place, with 1.0 percent, still a rise on the January 2006 figure when it ranked fourteenth globally.

The vast majority of spam is now being generated through spam relays – PCs that have been taken over in an illicit fashion – with the purpose of sending unwanted email while hiding the sender’s identity.

The decline in the US figures was down to a combination of better legislation and the fact that computer users were now protecting their computers, said Graham Cluley of Sophos.

"We're seeing spammers being successfully brought to justice in the US, but it's important to remember that they can be based anywhere in the world,” he said.

On a continent basis, Asia now headed the spam-sending list with 42.5 percent, with North America second on 25.6 percent, Europe third with 25 percent. South America, Australasia and Africa accounted for the remainder.

The figures are compiled by Sophos after analysing spam that has arrived in the company’s “spam traps”.