Web browser warnings should help protect people from malware, phishing, and network attacks. Adhering to warnings keeps people safer online. Recent improvements in warning design have raised adherence rates, but they could still be higher. And prior work suggests many people still do not understand them. Thus, two challenges remain: increasing both comprehension and adherence rates. To dig deeper into user decision making and comprehension of warnings, we performed an experience sampling study of web browser security warnings, which involved surveying over 6,000 Chrome and Firefox users in situ to gather reasons for adhering or not to real warnings. We find these reasons are many and vary with context. Contrary to older prior work, we do not find a single dominant failure in modern warning design---like habituation---that prevents effective decisions. We conclude that further improvements to warnings will require solving a range of smaller contextual misunderstandings.

In Apple's iOS 6, when an app requires access to a protected resource (e.g., location or photos), the user is prompted with a permission request that she can allow or deny. These permission request dialogs include space for developers to optionally include strings of text to explain to the user why access to the resource is needed. We examine how app developers are using this mechanism and the effect that it has on user behavior. Through an online survey of 772 smartphone users, we show that permission requests that include explanations are significantly more likely to be approved. At the same time, our analysis of 4,400 iOS apps shows that the adoption rate of this feature by developers is relatively small: around 19% of permission requests include developer-specified explanations. Finally, we surveyed 30 iOS developers to better understand why they do or do not use this feature.

Both academic research and historical incidents have shown that unstable BGP speakers can have extreme, undesirable impacts on network performance and reliability. Large amounts of time and energy have been invested in improving router stability. In this paper, we show how an adversary in control of a BGP speaker in a transit AS can cause a victim router in an arbitrary location on the Internet to become unstable. Through experimentation with both hardware and software routers, we examine the behavior of routers under abnormal conditions and come to three conclusions. First, that unexpected but perfectly legal BGP messages can place routers into those states with troubling ease. Second, that an adversary can implement attacks using these messages to disrupt the function of victim routers in arbitrary locations in the network. And third, modern best practices do not blunt the force of these attacks sufficiently. These conclusions lead us to recommend more rigorous testing of BGP implementations, focusing as much on protocol correctness as on software correctness.

Smartphone applications pose interesting security problems because the same resources they use to enhance the user experience may also be used in ways that users might find objectionable. We performed a set of experiments to study whether attribution mechanisms could help users understand how smartphone applications access device resources. First, we performed an online survey and found that, as attribution mechanisms have become available on the Android platform, users notice and use them. Second, we designed new attribution mechanisms; a qualitative experiment suggested that our proposed mechanisms are intuitive to understand. Finally, we performed a laboratory experiment in which we simulated application misbehaviors to observe whether users equipped with our attribution mechanisms were able to identify the offending applications. Our results show that, for users who notice application misbehaviors, these attribution mechanisms are significantly more effective than the status quo.

Decoy Routing is a new approach to Internet censorship circumvention that was recently and independently proposed at FOCI'11, USENIX Security'11 and CCS'11. Decoy routing aims to hamper nation-state level Internet censorship by having routers, rather than end hosts, relay traffic to blocked destinations. We analyze the security of these schemes against a routing capable adversary, a censoring authority that is willing to make routing decisions in response to decoy routing systems.