Abstract-To simulate crowds at mass events, realistic movement data of people is required. Despite their limited capacity for approximating real human mobility, synthetic movement models are traditionally used for this purpose. More realistic simulations can be achieved by using real-life movement data, gathered by observing people in the desired context. This paper presents a method for tracking people at mass events without the need for active cooperation by the subjects. The mechanism works by scanning at multiple locations for packets sent out by the Wi-Fi interface on visitors' smartphones, and correlating the data captured at these different locations. The proposed method can be implemented at very low cost on Raspberry Pi computers. This implementation was trialed in two different contexts: a popular music festival and a university campus. The method allows for tracking thousands of people simultaneously, and achieves a higher coverage rate than similar methods for involuntary crowd tracking. Moreover, the coverage rate is expected to increase even further as more people will start using smartphones. The proposed method has many applications in different domains. It also entails privacy implications that must be considered when deploying a similar system.
We present two novel noncooperative MAC layer fingerprinting and tracking techniques for Wi-Fi (802.11) enabled mobile devices. Our first technique demonstrates how a per-bit entropy analysis of a single captured frame allows an adversary to construct a fingerprint of the transmitter that is 80.0 to 67.6 percent unique for 50 to 100 observed devices and 33.0 to 15.1 percent unique for 1,000 to 10,000 observed devices. We show how existing mitigation strategies such as MAC address randomization can be circumvented using only this fingerprint and temporal information. Our second technique leverages peer-to-peer 802.11u Generic Advertisement Service (GAS) requests and 802.11e Block Acknowledgement (BA) requests to instigate transmissions on demand from devices that support these protocols. We validate these techniques using two datasets, one of which was recorded at a music festival containing 28,048 unique devices and the other at our research lab containing 138 unique devices. Finally, we discuss a number of countermeasures that can be put in place by mobile device vendors in order to prevent noncooperative tracking through the discussed techniques.
Abstract-Large crowds at music festivals or other mass events create challenging environments for traditional infrastructure based wireless networks. Mobile devices carried by the attendees produce large amounts of network traffic that can result in network outage or serious delays. Opportunistic networks may offer solutions to enable communication between attendees and/or organizers through direct communication between devices, without requiring a fixed infrastructure. In previous work, researchers have developed numerous opportunistic routing protocols designed to enable communication in such ad hoc networks. In this paper, several of these protocols are evaluated for the specific use case of a music festival by running simulations that make use of realistic mobility data collected during an international music festival. This analysis allows for identification of candidate routing protocols that exhibit properties that make them suitable for the envisaged scenario. The goal is to narrow down the set of candidate protocols and to eventually fine tune them to optimize their working. Based on the simulations, we propose two candidate routing protocols that are most suited for use at mass events.
Smartphones and other mobile devices have proliferated in the past five years. The expectation of mobile device users to always be online has led to Wi-Fi networks being offered by a variety of providers. Using these networks introduces multiple security risks. In this work, we assess to what extent the privacy stance of mobile device users corresponds with their actual behavior by conducting a study with 108 participants. Our methodology consists of monitoring Wi-Fi networks that the participants' devices connect to and the connections made by apps on these devices, for a period of 30 days. Afterwards, participants are surveyed about their awareness and privacy sensitiveness. We show that while a higher expertise in computer networks corresponds to more awareness about the connections made by apps, neither this expertise nor the actual privacy stance of the participant translates to better security habits. Moreover, participants in general were unaware about a significant part of connections made by apps on their devices, a matter that is worsened by the fact that one third of Wi-Fi networks that participants connect to do not have any security enabled. Based on our results, we provide recommendations to network providers, developers and users on how to improve Wi-Fi security for mobile devices.
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