A netwar is a form of low-intensity conflict that is waged by netizens, or people on the Internet (referred hereafter as networked actors), which include criminal organizations, transnational terrorists, social movement groups and activist groups.
The war is waged through decentralized and flexible network structures. It essentially refers to the conflict being waged over the Internet and networked systems such as information mobilization, hackings and counter-hackings, and, to a lesser extent, even very simple heated arguments over random topics between groups or cells.
Techopedia explains Netwar
Netwar is a concept unique to the Internet and information technology industry as a whole. It was introduced in the early 1990s by RAND Corporation, a US government-funded think-tank. The essence of netwar is the emerging forms of conflict in which the participants (i.e., networked actors) are made up of scattered groups and networks rather than of a cohesive institution whose main aim is to use knowledge, understanding and information in order to achieve a goal rather than to explicitly control physical resources and territory, which characterizes traditional wars.
Networked actors are a collection of people and groups without a clear hierarchy of command and who communicate through "all points" of communication channels with considerable aggregate bandwidth and have a global reach through the Internet. In contrast, highly institutionalized organizations such as the police and the armed forces communicate in highly hierarchical and centralized channels. As a point of comparison, cyberwar often revolves around a militaristic use of networked interfaces such as espionage and sabotage, whereas netwar is characterized more by massive information drives designed to enlighten the general public of specific information usually held secret by larger institutions.