The strategic rivalry between the United States and China is out in full swing in Southeast Asia. As the result, ASEAN is emerging both as a key player as well as a playground for pivotal global and regional actors. South Korea, Japan, and China known as ASEAN Plus Three, have strong economic, political, and technological ties with the region, and have leveraged their cyber capabilities to compete for influence in the region. This study evaluates the relative performances of the Plus Three’ cyber outreach efforts to the region by visualizing the complex web of actors and cyber cooperation and assistance activities with network analysis tools and open-source databases. We quantitatively analyze national cyber security cooperation of ASEAN including South Korea, Japan, and China through capacity building indicators and social network methodology. This study (1) analyzes cybersecurity cooperation in ASEAN Plus Three, (2) explores factors that influence cooperation, and (3) lays out a quantitative basis for establishing national information policy and cybersecurity strategy. We find that the Plus Three, despite the outward similarity in their respective regional strategies, are a study of contrasts, with one of them emerging as an influential yet silent power in the regional cyber diplomacy domain.