The U.S. has by far the highest number of bot-infected computers of any country in the world, with nearly four times as many infected PCs as the country in second place, Brazil. The quarterly report on malicious software and Internet attacks shows that while some of the major botnets have been curtailed in recent months, the networks of infected PCs still represent a huge threat. The data on botnets, published in Microsoft s Security Intelligence Report for the first half of 2010, paints a somewhat bleak picture of the botnet landscape.
Source: https://threatpost.com/us-reigns-most-bot-infected-country-101310/74570/