The new media enable entirely new ways of collaborations, that open unprecedented opportunities for handling tasks of extraordinary size or complexity. The most prominent example of such value production is Wikipedia (WP), a free, collaborative, multilingual Internet encyclopedia. It evolves without the supervision of an a priori selected expert team, its voluntary editors define its rules and maintain its quality. The size of WP is unquestionably superior to any other encyclopedia and by today it has become the number one reference in practice. As every edit and discussion post is recorded and available for investigation, WP is particularly well suited to study Internet based collaborative processes. While most articles evolve in a smooth, constructive manner, the history of WP pages is not always peaceful; there are sometimes heavy fights called edit wars between groups representing opposing opinions. The WP community has created a full system of measures to resolve conflict situations including the so called "three revert rule", locking articles for non-registered editors, tagging controversial articles, temporal or final banning of vicious editors. In spite of all these regulations it remains an interesting question, how conflicts emerge and get resolved. We present a new, efficient method for automatically detecting edit wars in Wikipedia and apply this method to six different language WPs. We discuss how the number of edits, reverts, the length of discussions, the burstiness of edits and reverts deviate in such pages from those following the general workflow and argue that earlier work has significantly over-estimated the contentiousness of the Wikipedia editing process. Using our measure of controversiality we analyze the temporal evolution of conflict pages and identify three different categories: i) localized, single issue conflicts, ii) localized, multiple issue conflicts, iii) permanent war.