90 percent of all spam comes from bots, says anti-spam technologist Matt Sergeant. Botnets tend to operate in multiple stages: A user may first get infected by a piece of malware, but by the time AV detects it, the malware will have downloaded a second stage of malware. Antivirus (AV) technology struggles when it comes to bot infections, he says. The biggest risk is a denial-of-service (DOS) attack, so there are potential consequences.”]
Source: https://www.darkreading.com/analytics/how-to-root-out-bots-in-your-network