botnet

noun2

1. •
   (Internet) A collection of compromised computers that is gradually built up and then unleashed as a DDOS attack or used to send very large quantities of spam.

   • Then they blacklisted addresses used by spammers. In response, senders started using botnets (networks of otherwise innocent computers). — 2010
2. •
   spyware

   • Google Chrome is botnet, use Firefox instead