Bots and Zombies

Taken from Hacker News

8. Definition: A zombie (sometimes also a bot) is a computer that is controlled remotely, either partially or fully, by an attacker. An attacker would have a network of zombies or a zombie army (sometimes across the world) that are already compromised / infected by attackers and are used for attacking other systems.
   
   Bots are used to initiate attacks, like denial of service, on other systems. These attacks are carried out by pooling the infected systems so that the impact can match the scale required (that is, to use as many bots as needed to crash the system.) A network of bots is called a botnet, and the attacker is the controller or herder of the bots.
   
   Reason for the name: Bot is a shorthand for 'robot', and zombie is due to the army-like nature of malicious robots.
   Propagation: A device first gets infected. Then, when the attacker decides so, he or she sends a remote command to the bot to make it start doing its malicious action.
   Examples of well-known botnets: the Mirai botnet and the Miner botnet.