CSIS argues that North Korean cyber operations, alongside activity from China and Russia, are creating a transnational threat environment that current U.S.-ROK cyber cooperation is not yet structured to deter or withstand. The core recommendation is a joint cyber resilience strategy built on shared situational awareness, stronger attribution, and more proactive or active cyber defense. The authors introduce a Cyberattack Severity Classification Framework to help Washington and Seoul make more consistent decisions after cyber incidents. The policy approach links cyber defense with law enforcement, financial measures, and diplomacy, which matters for DPRK-focused tracking because North Korean operations often blend espionage, disruption risk, and sanctions-evasion finance.