Bots are often precipitated by unsecured, always-on broadband connections, which allow the code to spread undetected from one machine to another. DDoS attacks using bots have reached nearly 10GB of aggregate attack bandwidth. Individual infected hosts often don’t know they’re infected or that they’re infecting others and spreading spam. Diagnosis can be hard to identify, but antispyware programs can be used to monitor the presence of bots. Treatment of infection often entails the pain of reimaging machines to eradicate the bots.”]
Source: https://www.csoonline.com/article/2118814/how-to-tell-if-you-have-bots.html