100 UK ISPs were invited to respond to a number of questions that investigated which areas of business were causing them the most concern. The key issue was the potential disruption to service that spam zombie machines can cause. 92% of respondents highlighted difficulties ISPs face in differentiating services from competitors and identifying new sources of revenue and dealing with the concerns of subscribers on the security of the service being delivered. Gartner estimates that up to 70% of all spam is generated by zombie infected machines. The majority of survey respondents recognised that providing customers with a guaranteed.”]
Source: https://www.darkreading.com/attacks-breaches/isps-hate-zombies