JULY 2025
Forging Forward
South Korea’s Proactive Cyber Defense and
Strategic Cooperation with the United States
By Joohui Park and Donghee Kim
Introduction
When countries design their cyber defense strategies, they do so on the premise that they can defend
against malicious cyber operations only after the impacts of such acts materialize. Instead of taking
this reactive posture, however, the United States spearheaded a paradigm shift to a proactive posture
in 2018, when the Department of Defense (DOD) developed the “Defend Forward” stratey. This
posture has since been maintained in the United States, and was rearmed in the introduction of the
2023 Department of Defense Cyber Stratey. Variations on this approach have been adopted by
some countries, including the Republic of Korea (ROK). South Korea introduced a proactive approach
to cyber defense in its 2024 National Cybersecurity Stratey, some aspects of which mirror the DOD’s
Defend Forward.
Proactive cyber defense is just one option available to countries responding to cyber threats. In
general, response options are various and can be structured with a range of typologies. For instance,
options can diverge into defensive and oensive responses; defensive responses, in turn, can be
classied as either reactive or proactive. Public attribution and countermeasures under international
law are examples of reactive defense; proactive defense can include active cyber defense and other
threat-hunting activities. In certain circumstances, alternatives to proactive cyber defense can be
more eective. This paper is based on this conceptualization.
For proactive defense, countries need to glean insights into adversaries’ acts in cyberspace
before their impacts reach the intended targets. These insights are mostly embedded in physical
infrastructures that adversaries exploit for malicious cyber operations—facilities primarily located
in foreign territories. That is why working with allies and partners is crucial for proactive cyber
defense. Fortunately, South Korea and the United States have made a great eort to cooperate in this
space over the last few years. Such cooperation is primarily based on the alliance between the two
