" The magic used in the map’s creation is advanced and impressive; it includes the Homonculous Charm, enabling the possessor of the map to track the movements of every person in the castle, and it was also enchanted to forever repel (as insultingly as possible) the curiosity of their nemesis, Severus Snape. "

― J.K. Rowling , Hogwarts: An Incomplete and Unreliable Guide (Pottermore Presents, #3)