As an emerging and thriving research branch, information security economics has recently drawn significant attention from practitioners and academics. Traditionally, both decision and static game theoretical techniques are employed to characterize the strategies of firms and hackers. However, these techniques fail to capture the dynamic attribute of the risk environment, which is an increasingly important element, especially in modern distributed and complex computer and communication networks. Utilizing a differential game framework in which hackers disseminate security knowledge within a hacker population over time, this paper analyzes dynamic interactions between a firm endeavoring to protect its information assets and a hacker seeking to misappropriate them. In particular, we investigate three differential games in which the firm and the hacker move simultaneously and sequentially, respectively. We find that (a) the hacker invests the most in the simultaneous differential game, whereas the firm, as the leader, invests the most in the sequential differential game, and (b) both the firm and the hacker enjoy their highest payoffs in the sequential differential game with the hacker as the leader. Furthermore, it is numerically shown that in equilibrium, knowledge dissemination may not necessarily benefit the hacker and harm the firm. Some of our results are consistent with the findings of previous work, although the earlier results were obtained from a static game framework. Our main findings contrast with those of several previous studies that showed mixed results for comparisons between simultaneous and sequential games.