Security and Privacy Issues

C rowdsensing—the crowdsourcing of sensor data—allows for real-time data gathering with greater reach and accessibility than traditional crowdsourcing, because it leverages personal mobile devices as its sensor nodes (see Figure 1). This makes large-scale participatory sensing viable with little or no infrastructure cost, and because mobile device users can freely move around, coverage of sensor nodes is easily scalable. Some crowdsensing applications also exploit the spatial properties of a problem space. In these spatial crowdsensing applications, a requester can ask for resources—which always include multimedia data—related to a specific location, and mobile users who accept the task travel to that location to obtain the multimedia data. With the ubiquity of smartphones equipped with various sensors and powerful networking capacities, such spatial multimedia crowdsensing has become increasingly prominent, but understanding the related safety and privacy concerns is extremely important when promoting participation and ensuring safe use of the data collected. Multimedia crowdsensing activities often take place on participants’ personal devices, so sensitive information can be inadvertently revealed (such as home and work locations and the routes used when commuting). Furthermore, the crowdsourcers—that is, the companies or institutions initiating the crowdsensing—cannot entirely trust data provided by the volunteers, because personal devices can be exposed to unsafe third-party access points (such as Wi-Fi) or contaminated with malicious code (viruses and malware), which could pose challenges to the veracity of the transmitted information.1,2 Here, we identify security and privacy issues in multimedia crowdsensing and look into existing works that aim to overcome these issues.