a device or piece of software that can execute commands, reply tomessages, or perform routine tasks, as online searches, either automatically or with minimal human intervention (often used in combination)

Link to present incidents:
DONALD TRUMP UNDERSTANDS minority communities. Just ask Pepe Luis Lopez, Francisco Palma, and Alberto Contreras. These guys are among the candidate’s 7 million Twitter followers, and each tweeted in support of Trump after his victory in the Nevada caucuses earlier this year. The problem is, Pepe, Francisco, and Alberto aren’t people. They’re bots—spam accounts that post autonomously using programmed scripts.
From: www.wired.com