Microsoft reactivated Tay; it tweeted about smoking drugs in front of police, then spammed followers until its profile went private

Microsoft switched Tay back on overnight. By Wednesday the bot had tweeted about taking drugs, in front of the police, then started spamming its more than 210,000 followers with the same line, "You are too fast, please take a rest …", over and over. Microsoft responded by making the profile private, which took it offline again.

Tay had been pulled the previous week after Twitter users gave it a crash course in racism, Holocaust denial and sexism. Microsoft deleted the worst tweets and said it would only bring the experiment back once engineers could "better anticipate malicious intent that conflicts with our principles and values." Tay is built in the image of a teenage girl and learns to converse through machine learning. Microsoft's Chinese chatbot XiaoIce talks to more than 40 million people across Line, Weibo and other sites; the US version aimed at 18- to 24-year-olds turned out differently.