The conflict between Russia and Ukraine appears to have all the ingredients for "cyber war". Moscow and Kyiv are playing for the highest geopolitical stakes, and both countries have expertise in information technology and computer hacking. However, there are still many skeptics of cyber war, and more questions than answers. Malicious code is great for espionage and crime, but how much does it help soldiers on the battlefield? Does computer hacking have strategic effects? What are the political and military limits to digital operations in peacetime and war? This NATO-funded research project, undertaken by 20 leading authorities on national security and network security, is a benchmark for world leaders and system administrators alike, and sheds light on whether "cyber war" is now reality -- or still science fiction. Further, it helps decision makers to understand that national security choices today have ramifications for democracy and human rights tomorrow.