Firms adopt blockchain technology (BCT) to provide secure internal database functionality and secure external digital transactions. However, these firms can encounter hacks because of BCT vulnerabilities. Extant qualitative studies suggest conflicting perspectives regarding the legitimacy of blockchain security. Prior literature on BCT adoption and information security has not specifically examined the universal legitimacy of this adoption. As a result, current knowledge of the relationship between BCT adoption and information security is not well established. Our longitudinal study applies institutional theory that distinguishes between symbolic and substantive BCT adoption. Symbolic BCT adoption merely offers stakeholders the perception of technological advancement without actual blockchain implementation. Conversely, substantive adoptions create tangible and concrete changes in organizational routines, aligning with the maximization of a meaningful impact on the firms. Our empirical analysis provides revelatory insights that demonstrate substantive BCT adoptions reduce data breaches caused by insider threats.