Incidents of cyber security breaches are on the rise and pose a potential threat to businesses. Especially for publicly traded firms as they could create a long-lasting influence on their financial performance and, thus, the market value (MV) of a firm. Following the footsteps of the efficient market hypothesis, previous studies have examined only the short-run impact on MV ensuing to security breach announcements. Therefore, this study aims to conceptualize the impact of security breaches on MV as manifested by long-run abnormal returns those firms. The study is expected to provide a meaningful insight to investors and managers on the long-run interconnection between cyber security breaches and firms� market value. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.