A survey released Thursday said that nearly all the world's spam is spewed by a limited number of hard-core spammers within the United States.
Based on analysis of the spam it blocked for its 1,000-plus clients during May, June, and July, message filtering firm CipherTrust said that 86% of all spam originated in the United States.
Although U.S.-based IP addresses accounted for only 28% of the total addresses used to spam--tying South Korea for the top spot--spammers overwhelmingly favor U.S. domains. Messages from Korean IP addresses, in comparison, accounted for just 3% of all spam. Similarly, China and Hong Kong, where about 23% of all spamming IP addresses reside, account for just 2.6% of all spam.
"That was quite a surprise," said Dmitri Alperovitch, a research engineer at CipherTrust. "The percentage of spamming IP addresses within the U.S. is in line with other surveys, but in the actual number of messages, the U.S. is responsible for the vast bulk of spam."
CipherTrust's numbers run counter to those in other surveys, which claim that a much larger percentage of spam comes from outside U.S. borders. Commtouch, for example, recently estimated that the U.S. accounted for only 56% of the world's spam.
Alperovitch defended his company's data by pointing out that other studies rely on spam-gathering honey pots, while CipherTrust tallies only those actual messages it intercepts. "Those two approaches are quite different," he said, "because some spammers are actually targeting specific companies with messages that the honey pots wouldn't see."
CipherTrust's numbers also bolstered the long-held theory that a few kingpin spammers are responsible for most of the spam. "The bulk of U.S. spam is coming from a very limited set of IPs with high-bandwidth connections," said Alperovitch, who estimated that the high-volume spamming addresses number fewer than 10,000 and the number of spammers at less than 200.
The United States is the origin of choice for spammers, said Alperovitch, because of the plentiful supply of cheap high-speed bandwidth. "Spammers need big pipes, and they don't want to pay much for it," he said.
That explains the low percentage of spam messages originating from overseas' IP addresses. The lack of cheap bandwidth outside the United States is stymieing spammers' attempts to scale up the volume of their mailings to U.S. sizes. In fact, the majority of spam that does come from countries other than the United States originates with zombies--hijacked computers typically with high-speed, high-volume access to the Web, giving spammers a free ride, bandwidth-wise.
Zombies are less of a problem in the United States, said Alperovitch, because of the inexpensive access spammers can buy here, as well as some recent efforts by major Internet providers to clamp down on zombies.
Cable provider Comcast, for instance, launched an effort in May to block its members' cable-connected machines from being used by spammers; it claimed a one-third reduction in spam coming out of its network. "We also saw a significant drop-off in spam from Comcast after May," said Alperovitch, who added that the decrease was in the 30% range.
Although the United States has anti-spam laws in place at both the states and federal levels--the latter through the Can-Spam Act that went into effect in January--critics have said that fighting spam locally doesn't do any good when the problem's global.
CipherTrust's numbers may mean it's possible to put at least a partial lid on spam through laws and enforcement solely within the United States. "Enforcement of Can-Spam could go a very long way toward reducing spam," Alperovitch said.