According to Solutionary's Security Engineering Research Team (SERT) Quarterly Threat Intelligence Report for Q4 2013, the United States was the leading malware-hosting nation in the fourth quarter of last year, hosting 44 percent of all malware.
The U.S. hosted five times more malware than the second-leading malware-hosting nation, Germany, which was responsible for 9 percent of all malware in Q4 2013.
"We aren’t just talking about foreign espionage campaigns, APTs and breaches; many of these malicious activities are taking place within U.S. borders," Solutionary SERT director of research Rob Kraus said in a statement. "Malware and, more specifically, its distributors are utilizing the technologies and services that make processes, application deployment and website creation easier."https://o1.qnsr.com/log/p.gif?;n=203;c=204660766;s=9477;x=7936;f=201812281312070;u=j;z=TIMESTAMP;a=20392931;e=i
The full report is available here.