<p>Some types of Internet security countermeasures require cooperative adoption to effectively defend against cyberattacks, such as authentication mechanisms that prevent spoofing attacks. In these mechanisms, both the information source and the receiver must participate: the source signs the information, and the receiver verifies it. Adoption by only one party is insufficient, creating a social dilemma where cooperative adoption maximizes social welfare, but individual incentives diminish if others do not adopt. Resource Public Key Infrastructure (RPKI) is an example of such a mechanism, protecting against spoofing in Internet routing. Its effectiveness depends on the adoption rate across network paths and has been hindered by a low adoption ratio. However, recent trends show a moderate increase in RPKI adoption. This paper investigates the reasons behind this adoption, considering the roles of altruism, bounded rationality, and the influence of network externality. Through multi-agent simulations, we explore how these factors interact. Our findings suggest that while bounded rationality is crucial for overcoming the social dilemma, the effect of altruism is limited, and the underlying network externality also plays a significant role in facilitating spontaneous adoption across the network. These insights have implications for both network operators and policymakers in designing strategies to promote the widespread adoption of security technologies.</p>