Browse Theses

Wireless networks are built upon a shared medium that makes it easy for adversaries to conduct radio interference, or jamming attacks, which effectively cause a denial of service (DoS) of either transmission or reception functionalities. These attacks can be easily accomplished by an adversary by either bypassing MAC-layer protocols, or emitting a radio signal targeted at jamming a particular channel. In this thesis, we examine the issue of jamming wireless networks, and sensor networks in particular, by studying both the attack and defense side of the problem. On the attack side, we present four different jamming attack models that can be used by an adversary to disable the operation of a wireless network, and evaluate their effectiveness in terms of how each method affects the ability of a wireless node to send and receive packets. In order to cope with the problem of jamming, we discuss a two-phase strategy involving the diagnosis of the attack, followed by a suitable defense strategy. For detection, we show that single measurement statistics are not enough to reliably classify the presence of a jamming attack, and propose multimodal detection methods. To cope with jamming, we propose a technique, channel surfing, which involves evading the interferer in the spectral domain. Several different channel surfing models are presented, and we evaluate their effectiveness using a testbed of MICA2 motes. Beyond channel surfing, we overview a second defense strategy whereby it is possible to establish a low data rate jamming resistant communication channel by modulating the interarrival times between jammed packets.