The Intruder Charm was introduced by Professor Ivy Knox in early 2081 (Term 34). Not to be confused with the Caterwauling Charm, the Intruder Charm provides a local alarm over a finite area. The Caterwauling Charm provides a pervasive, annoying wailing sound that can be heard over a greater distance.
The incantation is Intrudus Concutio (in-TROO-duss con-COO-shee-oh).
To successfully cast an Intruder Charm, one must say the incantation while tracing the area one wishes to cover by this charm. Not only does the Intruder Charm detect when someone enters by door or window, it can also detect if they enter a room by other means, such as apparition, portkeys, floo, etcetera. If one wants to cover a whole room or house with this spell in order to detect when someone enters by other magical means, one would verbally repeat the incantation whilst tracing your wand around the perimeter of the room or the house.