A clandestine cell system is a way of organising a group of people so that it is kept secret. This is so the group are better able to resist infiltration or discovery by an enemy. If a person only knows the others in the person's cell, then they cannot betray the others outside of his or her cell, either accidentally, or under interrogation. The cell can range from a strict hierarchy of people to a team of people. It is used by spy agencies, criminal organisations and guerilla and terrorist groups.