A British computer security firm says South Korea ranks 2nd in its list of 12 spam-producing countries.

"Sophos" said Wednesday that the U.S. topped the list by producing 42.5 percent of annoying and often dangerous spam e-mails, far ahead of South Korea's 15.4 percent.

Sophos said it came up with what it called the "dirty dozen list" of spam producing nations after scanning all spam messages received at its global network of e-mail "honeypots" in the last month.

The firm said South Korea, with the most broadband users in the study, has nearly tripled the percentage of spam originating from its shores since February.

South Korea was followed on the list by China, Brazil and Canada.