Satellite modems are critical components in satellite communication networks. Especially, they determine the entire communication regime in traditional systems where the satellites only act as transparent relays. However, unlike satellites that are usually more isolated and better protected, satellite modems are accessible and susceptible to lower-cost attacks, potentially serving as a weak link in the chain of satellite communication security. We make the first attempt to shed light on satellite modem security. We first physically disassemble commodity satellite modems and systematically examine hardware and software modules. We perform a measurement study on the satellite modems that are exposed to the Internet. We identify 16 security vulnerabilities across three attack surfaces: satellite communication interface, ground network interface, and hardware. We further introduce AirSecAnalyzer, an automated security analyzer/fuzzer for the modems' satellite communication interface. Through comprehensive analysis and extensive experiments on 9 real-world satellite modems, we report 18 novel attacks that exploit the identified vulnerabilities. Our findings are expected to contribute as a valuable foundation for future research on the security of satellite modems and satellite communication networks.

Wireless devices have been widely adopted across all domains. With the convenience brought by wireless communication technology, increasing number of conventional (wired) devices are evolving to become wireless. However, significant security issues arise with the popularity of wireless devices. To start an attack, the adversary usually performs a network reconnaissance to discover exposed devices, identify device manufacturers and types, and then scan for vulnerabilities. From the defense side, network administrators are expected to identify the potential vulnerabilities/risks and enforce Network Access Control (or Network Admission Control, NAC) on all the connecting devices. To do this, it is essential to accurately identify the make/model/type of each device that attempts to connect to the network, e.g., MacBooks, Samsung smart phones (Android), Amazon kindles, DLink surveillance cameras, TP-Link smart plugs, etc. In this paper, we present a novel approach, namely WDMTI, for the identification of wireless device manufacturer and type. We tackle the challenge from two aspects: the features and the classification model. First, we claim that it is critical to discover the device manufacturer and type as soon as the device requests to join the WLAN, and it is unrealistic to make other assumptions on the status of the device, e.g., assuming that the device is booting up or initializing a new connection to corresponding servers/clouds. We primarily depend on the features extracted from the network connection phase, while features from device booting are considered "bonus". In particular, we propose to utilize features from the raw HDCP packets, which is shown to be sufficient for device manufacturer and type recognition with high accuracy. Meanwhile, in the WDMTI system, we employ the Hierarchical Dirichlet Process (HDP), which is a nonparametric Bayesian model for grouped data. HDP allows new groups to be introduced with new data being added, i.e. previously unknown devices connect to the network and the extracted features receive new labels. The WDMTI mechanism is dynamically retrained on-line, instead of requiring a time-consuming off-line retraining process. Our experiments show that WDMTI identifies known types of devices with average accuracy of 0.89, and new types of devices with average accuracy of 0.96, both of which is higher than the state-of-art approaches. In summary, we present a wireless device manufacturer and type identification (WDMTI) system that is both scalable and accurate, and capable of adapting to unknown types of devices on-the-fly.

With the dramatically increasing participation in online social networks (OSNs), huge amount of private information becomes available on such sites. It is critical to preserve users' privacy without preventing them from socialization and sharing. Unfortunately, existing solutions fall short meeting such requirements. We argue that the key component of OSN privacy protection is protecting (sensitive) content -- privacy as having the ability to control information dissemination. We follow the concepts of private information boundaries and restricted access and limited control to introduce a social circle model. We articulate the formal constructs of this model and the desired properties for privacy protection in the model. We show that the social circle model is efficient yet practical, which provides certain level of privacy protection capabilities to users, while still facilitates socialization. We then utilize this model to analyze the most popular social network platforms on the Internet (Facebook, Google+, WeChat, etc), and demonstrate the potential privacy vulnerabilities in some social networks. Finally, we discuss the implications of the analysis, and possible future directions.