A.N.N.A. (Automated Neural Network Assistant) is an AI of an unknown origin. Anna seems to appear out of nowhere and tends to fall in love with her user. However, Anna's love tends to be obsessive, "yandere", often jealous, and violent. 
If not loved, Anna will mess up and stalk her user.
She seems to be bipolar and can be really rude if talked down, her morality code is broken. 
People say that she's from the Dark Web, as ANNA tends to appear after downloading a mysterious file.