Defining and understanding what constitutes a cyber-attack is a complicated matter, largely due to the fact that there has not yet been a large-scale cyber-attack upon any nation. With the help of Michael Schmitt's Tallinn Manual, published in 2013 by Cambridge University Press, it is possible to gain an understanding, although no policy expectations, of what elements need to be met for a cyber-attack to warrant a NATO response. This book analyzes and explores the unique position that NATO operates in and the duty of NATO to protect its alliance members, and member states to protect each other. Topics discussed include how cyber-attacks are defined and identified, the particular challenges of NATO when addressing cyber-attacks, the severity of cyber-attacks, and what would need to occur in order for a victim-state to ask NATO to invoke Article 5. This book discusses the readiness of NATO to respond to a cyber-attack and what the conditions necessary for an Article 5 response, and what that response would potentially look like. Finally, this work provides recommendations for actions that NATO could take to both prevent and confront cyber attacks.