Leaderless resistance, or phantom cell structure, is a social resistance strategy in which small, independent groups (covert cells), including individuals (a solo cell called a "Lone Wolf"), challenge an established institution such as a law, economic system, social order, government, et cetera. Leaderless resistance can encompass anything from non-violent protest and civil disobedience to vandalism, terrorism and other violent activity. Leaderless cells lack bidirectional, vertical command links and operate without hierarchal command. While it lacks a central command, the concept includes a common goal between the individual actor and the group or social movement from which the ideology was learned.