According to AppRiver's mid-year Global Threatscape Report, the company screened more than 15 billion e-mails in the first half of 2013, almost 13 billion of which were spam -- and 171 million of which delivered malware.

The U.S. was the leading country of origin for spam e-mails in the first half of the year, while Belarus came second. The biggest news stories leveraged by spam campaigns in the last six months included the Boston Marathon bombings and the rise of mobile malware, according to AppRiver.

"The Internet has far evolved beyond a simple means to share information; it is now a tool to be used for nearly anything, good or bad," AppRiver security analyst Troy Gill said in a statement. "We've moved on from the whispers and suspicions of cyber espionage to governments openly discussing the fact that these are a common tactic for a new world. All sides, mostly, admit to either foraging for big data to help gain governmental or business advantages, or to directly attacking systems, or to pilfering through critical infrastructures."

AppRiver's mid-year Global Threatscape Report is available here.