Good Rolling Stone November 2016 article on Medium with this description of how botnets may operate:

“To explain how they work, Ben Nimmo, a fellow at the Atlantic Council’s Digital Forensic Research Lab, uses a shepherding analogy. “A message that someone or some organization wants to ‘trend’ is typically sent out by ‘shepherd’ accounts,” he says, which often have large followings and are controlled by humans. The shepherds’ messages are amplified by ‘sheepdog’ accounts, which are also run by humans but can be default-set “to boost the signal and harass critics.” At times, the shepherds personally steer conversations, but they also deploy automation, using a kind of Twitter cruise control to retweet particular keywords and hashtags. Together, Nimmo says, the shepherds and sheepdogs guide a herd of bots, which “mindlessly repost content in the digital equivalent of sheep rushing in the same direction and bleating loudly.””

Overall description bears similarity to the description of LOIC/Low Orbit Ion Cannon, as described in this February 2011 Wired article about the guy who brought the HB Gary leaks down on himself:

“The report that came back focused on the Low Orbit Ion Cannon, a tool originally coded by a private security firm in order to test website defenses. The code was open-sourced and then abandoned, but someone later dusted it off and added “hivemind mode” that let LOIC users “opt in” to centralized control of the tool. With hundreds or thousands of machines running the stress-test tool at once, even major sites could be dropped quickly.”