In 2009, the NATO Cooperative Cyber Defence Centre of Excellence (NATO CCD COE), an international military organization based in Tallinn, Estonia, and accredited in 2008 by NATO as a ‘Centre of Excellence’, invited an independent ‘International Group of Experts’ to produce a manual on the law governing cyber warfare. In doing so, it followed in the footsteps of earlier efforts, such as those resulting in the International Institute of Humanitarian Law’s San Remo Manual on International Law Applicable to Armed Conflicts at Sea and the Harvard Program on Humanitarian Policy and Conflict Research’s Manual on International Law Applicable to Air and Missile Warfare. The project brought together distinguished international law practitioners and scholars in an effort to examine how extant legal norms applied to this ‘new’ form of warfare. Like its predecessors, the Manual on the International Law Applicable to Cyber Warfare, or ‘Tallinn Manual’, results from an expert-driven process designed to produce a non-binding document applying existing law to cyber warfare.

Cyber operations began to draw the attention of the international legal community in the late 1990s. Most significantly, in 1999 the United States Naval War College convened the first major legal conference on the subject. In the aftermath of the attacks of 11 September 2001, transnational terrorism and the ensuing armed conflicts diverted attention from the topic until the massive cyber operations by ‘hacktivists’ against Estonia in 2007 and against Georgia during its war with the Russian Federation in 2008, as well as cyber incidents like the targeting of the Iranian nuclear facilities with the Stuxnet worm in 2010.