Security experts often question why some users take actions that could expose them to security and privacy risks. Using unsecured Wi-Fi networks is one common example. Even though mobile data is now a more secure means to connect to the Internet, and is becoming faster and more affordable, many users continue to use unsecured Wi-Fi. To identify risk mitigating strategies, the research community first needs to understand the underlying factors driving users' decisions. Previous studies examined stated preferences --- what people said they have done or think they would do --- but that may not truly reflect real-life behavior. This study is the first to examine revealed preferences --- what people actually do in naturalistic settings. Specifically, we investigated how users' desire to save mobile data and battery power influenced their decisions at the time when they connected to open unsecured Wi-Fi in the wild. We also examined whether the decision to use unsecured Wi-Fi networks could be driven by demographic factors and the user's perception of the risk associated with using these networks. We recruited 71 participants in the UK to install My Wi-Fi Choices, our own Android app, on their mobile device, and run it for three months in the background. The app captured details of mobile data allowance and battery power on participants' devices whenever they used open unsecured Wi-Fi networks. We found that depleting mobile data significantly drove participants to use these networks, especially when their remaining allowance reached approximately 30%. Battery level, however, did not play a significant role. The perceived risks of unsecured Wi-Fi did not affect the decision-making either. Age, education, and income level were also correlated with increased use of unsecured Wi-Fi.

Many people today use public Wi-Fi networks but they harbor security and privacy risks. We investigated the extent of these risk today, and what factors influenced users to use the networks, adapting the design of a previous UK study, this time in Japan. We first set up an experimental open public Wi-Fi network at ll locations in downtown Nara and captured Internet traffic. From approximately 7.7 million packets captured from 196 unique mobile devices during a 150-hour experiment, we found private photos, emails, documents, and login credentials being transmitted without encryption - showing that many people use unsecured public Wi-Fi networks, and many applications do not encrypt data they send. We then examined why people use public Wi-Fi in a range of scenarios through a survey with 103 participants. We found that the desire to conserve mobile data allowance was linked to a risk-taking attitude, and use of unsecured public Wi-Fi, especially among participants with a low monthly data allowance. Gender and education also played a role; female participants and those with high school education were more likely to use public Wi-Fi.