With almost all personal, social and national activities connected to the network, now we cannot imagine a world without the internet. The connectivity of economic activity is becoming denser and is gradually weakening the independence of nations. Many countries have been unable to develop their own economic and foreign policy, and a rise of warfare costs is decreasing the possibility that a country will unilaterally strike an all-out war. Cyber space which has already become a source of wealth, is becoming the epicenter of terrorism. As the real world and the virtual world get mixed up, the greater the connectivity, the more vulnerable we are to various terrorist threats. For the extreme terrorist group, there are more opportunities to do massive damage with cyber attacks. Cyber attacks can cause tremendous confusion and fear to victims or potential victims because it is difficult to track the epicenter. Almost every country, including the United States, China, Israel, Russia, Britain, and Japan, are building effective and robust systems to respond to any form of cyber threats. The most intense cyber warfare areas in the world are the United States versus China and Russia, Israel versus Arab countries, and the Republic of Korea with the best cyber infrastructure. Countries around the world are struggling to create a response system to fight against the upcoming cyber warfare by establishing an organization that is dedicated to cyber warfare. Beyond the defense measures to prevent cyber attacks, they are developing cyber weapons such as malicious codes and electronic bombs that can paralyze infrastructure of other countries, and have created a secret organization that is not part of any government sector in order to avoid retaliation.