Botnets are networks of remotely controlled compromised computers. Such infected hosts are controlled principally by a botmaster via a command and control center (C2) Botnets can be used for attacks including DDoS, click fraud, data harvesting, credential stuffing, vulnerability probing, phishing, astroturfing, and sockpuppeteering. Their distribution and scale makes them difficult for 3rd party services to detect and stop. Such compromised computers are called bots, zombies, drones, or infected hosts. The individual controlling a botnet is called a botmaster, botnet herder or bot herder.