"The United States is now home to the largest
percentage of botnet-infected computers, hosting 18 percent of all
zombie machines. Cybercriminals are building an army of infected,
"zombie" computers to recover from last November's takedown of a
central spam-hosting ISP, according to the new report from Avert
"The November 2008 takedown of McColo Corp. dropped spam levels
by an estimated 60 percent, but spam quantities are rising as
cybercriminals create new ways to send bulk e-mails.
"The quick expansion of botnets threatens to boost spam levels
back up. In fact, spam volumes have already recovered about 70
percent since McColo Corp. went offline. Compared with the same
quarter a year ago, spam volumes are 20 percent lower in 2009 and
30 percent below the third quarter of 2008, which had the highest
quarterly volumes recorded to date."