Doctor of Philosophy / Security Studies / Jeffrey J. Pickering / As the Internet is progressively integrated into industrial and defense-related networks around the globe, it is becoming increasingly important to understand how state and sub-state groups can use Internet vulnerabilities as a conduit of attack. The current social science literature on cyber threats is largely dominated by descriptive, U.S.-centric research. While this scholarship is important, the findings are not generalizable and fail to address the global aspects of network vulnerabilities. As a result, this dissertation employs a unique dataset of cyber threats from around the world, spanning from 1990 to 2011. This dataset allows for three diverse empirical studies to be conducted. The first study investigates the political, social, and economic characteristics that increase the likelihood of a state being targeted for cyber threats. The results show that different state characteristics are likely to influence the forms of digital attack targeting. For example, states that experience increases in GDP per capita and military size are more likely to be targeted for cyber attacks. Inversely, states that experience increases in GDP per capita and those that are more democratic are less likely to be targeted for cyber terrorism. The second study investigates the role that international rivalries play in cyber threat targeting. The results suggest that states in rivalries may have more reason to strengthen their digital security, and rival actors may be cautious about employing serious, threatening forms of cyber activity against foes because of concerns about escalation. The final study, based upon the crisis bargaining theory, seeks to determine if cyber threat targeting decreases private information asymmetry and therefore decreases conflict participation. Empirical results show that the loss of digital information via cyber means may thus illicit a low intensity threat or militarized action by a target state, but it also simultaneously increases the likelihood that a bargain may be researched, preventing full scale war by reducing the amount of private information held between parties.

This dissertation reexamines the often cited conclusion in diplomatic crisis bargaining that sunk cost signals, such as military mobilization and arms races, are inefficient compared to tied hands signals. This conclusion ignores the the investment potential that the most frequent examples of sunk cost signaling have in terms of increasing preparedness for war. Through a novel game theoretic model, I demonstrate that signals with a sunk investment can be optimal in comparison to tied hands signals. The conclusion of the model suggests that signals with a sunk investment, such as mobilization, have value as a hedged bet against deterrence, increasing in value as the investment would make the state more powerful in war, the state is pessimistic about deterrence, and the state is risk averse. I contextualize these conclusions in historical case studies of the Berlin Crisis and NATO intervention in Kosovo.

Audience costs, which are defined as political costs for a leader generated when the leader fails to follow through on international commitments, are an important concept in international relations to understand the causes of war and peace. However, despite its prominence, evidence for audience costs is mixed at best. In this dissertation, by conducting a series of survey experiments in the United States, I examine a variety of causal mechanisms and observable implications of audience cost models. In Chapter 2 I explore the role of the media. The result of a survey experiment shows that the media's negative framing of a leader's backing down from a threat increases audience costs, but only after subjects are informed of the leader's justification. Chapter 3 tests the idea that the magnitude of audience costs depends on an individual's personality traits. A pilot experiment using a sample of undergraduate students does not support this expectation. Lastly, I compare the credibility of public versus private threats in Chapter 4. A conjoint survey experiment demonstrates that as many proponents of audience cost theory suggest, public threats are perceived as more credible, and the sources of their credibility are domestic audience costs.

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