This study aims to present the necessary elements that should be part of South Korea’s National Defense Strategy against the recent North Korean cyber-attacks. The elements proposed in this study also reflect the recent trend of cyber-attack incidents that are happening in the Unites States and other countries and have been classified into the three levels of cyber incidents: cyberwarfare, cyberterrorism and cybercrime. As such, the elements proposed are presented in accordance with this classification system. In order to properly take into account the recent trend of cyber-attacks perpetrated by North Korea, this paper analyzed the characteristics of recent North Korean cyber-attacks as well as the countermeasures and responses of South Korea. Moreover, by making use of case studies of cyber-attack incidents by foreign nations that threaten national security, the response measures at a national level can be deduced and applied as in this study. Thus, the authors of this study hope that the newly proposed elements here within will help to strengthen the level of Korea’s cyber security against foreign attacks, specifically that of North Korea such as the KHNP hacking incidents and so on. It is hoped that further damage such as leakage of confidential information, invasion of privacy and physical intimidation can be mitigated.