ICSI in InformationWeek

“Inside The Booming Botnet Industry”
September 7, 2011  |  Mathew J. Schwartz, InformationWeek

excerpt: 
When running a botnet, attrition is constant, as security software on PCs finds and eliminates the malicious code that turned the PC into a botnet node. Accordingly, many "botmasters" outsource infections to what's known as pay-per-install (PPI) service providers. Going rates for infecting 1,000 unique PCs with malware range from up to $180 in the United States and Great Britain, from $20 to $160 for other parts of Europe, down to just $7 or $8 in parts of Asia.
research area: 
recap: 
Researchers have found that the majority of the most active malware distributors pay third parties to install their malicious software on at least some of the computers they infect.