It was mildly entertaining when hackers, presumably from North Korea, got into Sony Pictures computer systems and revealed snarky emails between studio executives. It's another story when hackers, some backed by their government, hack into businesses and even nuclear installations. Welcome to the new global battleground: cyberspace. So says the Director of the Digital and Cyberspace Program at the Council on Foreign Relations - Adam Segal. His new book The Hacked World Order: How Nations Fight, Trade, Maneuver, and Manipulate in the Digital Age, looks at how anyone with the internet, some malware and an email address can wage war.