Two complementary firms＇ information sharing and security investment are investigated. When two complementary firms with heterogeneous assets are both breached, it is assumed that they suffer different losses which are associated with their information assets. Some insights about optimal strategies for the firms and the attacker are obtained by the game theory, which forms a comparison with those derived from substitutable firms, and those derived from complementary firms with homogenous loss. In addition, both the unit transform cost of investment and the extent of firms＇loss affect the optimal strategies.Assuming that firms can control information sharing, security investments and both of them, respectively, the effect of the social planner is further analyzed on the information sharing, firms＇ aggregate defence, the aggregate attack and social total cost. Finally, some policy advice is provided through numerical simulation. Results show that firms are willing to choose security investment centrally rather than individually, but an intervention in information sharing by the social planner may not necessarily be preferable.
