The interdependency of information security risks poses a significant challenge for firms to manage security. Firms may over- or under-invest in security because security investments generate network externalities. In this paper, we explore how firms can use three risk management approaches, third-party cyberinsurance, managed security service (MSS) and risk pooling arrangement (RPA), to address the issue of investment inefficiency. We show that compared with cyberinsurance, MSS is more effective in mitigating the security investment inefficiency because the MSS provider (MSSP) serving multiple firms can endogenize the externalities of security investments. However, the investment externalities may discourage a for-profit MSSP from serving all firms even on a monopoly market. We then show that firms can use RPA as a complement to cyberinsurance to address risk interdependency for all firms. However, the adoption of RPA is incentive-compatible for firms only when the security investments generate negative externalities.