| The open and shared nature of the wireless medium makes it easy for adversaries to launch simple, yet effective, denial of service attacks (DoS attacks). As an example, jamming attacks, involve the uncoordinated transmission of electromagnetic energy on the medium. In a carrier sensing network (e.g., 802.11), this attack strategy increases the number of collisions at the receiver side and/or blocks the medium access to legitimate nodes at the transmitting side. Both of the above effects degrade the wireless network performance significantly. Frequency hopping (FH) has been traditionally used to overcome jamming attacks. However, we analytically and experimentally show that FH is inadequate to efficiently cope with jamming in today's networks.;Later we propose a suite of systems that aim at coping with jamming attacks at various levels (i.e., detection, localization and prevention). We first identify two intelligent and effective jamming attacks that can be launched in 802.11 WLANs and we provide robust detection systems. In particular, we design and implement (i) CMD, a system to detect active jamming attacks that exploit the carrier sensing functionality of 802.11 networks and (ii) FIJI, a cross-layer system for detecting (and mitigating) jamming attacks that exploit the performance anomaly of 802.11 WLANs. Furthermore, given the importance of locating the jamming device in many deployment scenarios (e.g., battlefield), we propose a lightweight jamming localization scheme. Our system utilizies ideas borrowed from the gradient descent optimization method. The system's evaluations, show the potentials and applicability of our localization strategy. The final step for coping with jamming attacks is jamming prevention. Based on our initial measurement driven analysis, we do not rely on a FH scheme, that tries to simply avoid the jammer. On the contrary, we design, implement and evaluate a prevention system, called ARES (Anti-jamming REinforcement System), to fight against the saboteur. ARES is applicable to carrier sensing networks and tunes the parameters of rate adaptation and power control to improve the performance under the presence of an attack while ensuring that operations under benign conditions are unaffected. Our extensive evaluations, show that ARES improves the network throughput across all scenarios by up to 150%. |
