Despite being seriously outnumbered, the U.S. managed to outmaneuver China to achieve spam dominance in the second quarter; Russia, meanwhile, continued to lurk in the shadows, pulling spam's concealed strings.

The U.S. remained the world's leading spamming country, accounting for 23.2 percent of all spam sent out in the second quarter, with China close behind at 20.0 percent, according to security company Sophos, writes TechWeb. Countries ranking third through fifth in the "Dirty Dozen" list - South Korea, France, and Spain - together accounted for only 17.5 percent of spam.

Image-based spam is rapidly increasing in popularity, accounting for 35.9 percent of all spam in June, nearly double January's 18.2 percent. The spam proliferation problem, says Sophos, is a consequence of zombies, or hijacked computers that are used to send out spam, usually without the computer owner's knowledge.

Though it's not a member of the dirty dozen, even the Vatican has emerged as an "unwitting relay source of spam traffic," according to Sophos, writes the Sydney Morning Herald; Italy did, however, make its first appearance on the "Dirty Dozen" list, in eighth position.

Although the list doesn't necessarily reveal where spam originated, it does identify the general location of the computers used to distribute it. Russia is "conspicuously absent" from the dirty dozen, Sophos says, but spammers there probably control extensive networks of zombies worldwide.