A lockdown is an emergency protocol that usually prevents people or information from leaving an area. The protocol can usually only be initiated by someone in a position of authority. Lockdowns can also be used to protect people inside a facility or, for example, a computing system, from a threat or other external event. Of buildings, a drill lockdown usually means that doors leading outside are locked such that no person may enter or exit. A full lockdown usually means that people must stay where they are and may not enter or exit a building or rooms within said building. If people are in a hallway, they should go to the nearest safe, enclosed room.