Sensor networks hold the promise of facilitating large-scale, real-time data processing in complex environments. Their foreseeable applications will help protect and monitor military, environmental, safety-critical, or domestic infrastructures and resources.In these and other vital or security-sensitive deployments, keeping the network available for its intended use is essential. The stakes are high: Denial-of-service (DoS) attacks against such networks may permit real-world damage to the health and safety of people. Without proper security mechanisms, networks will be confined to limited, controlled environments, negating much of the promise they hold. The limited ability of individual sensor nodes to thwart failure or attack makes ensuring network availability more difficult.To identify DoS vulnerabilities, we analyze two effective sensor network protocols that did not initially consider security. These examples demonstrate that consideration of security at design time is the best way to ensure successful network deployment. THEORY AND APPLICATIONAdvances in miniaturization combined with an insatiable appetite for previously unrealizable information gathering have led to the development of new kinds of networks. In many areas, static infrastructures are giving way to dynamic ad hoc networks.One manifestation of these trends is the development of highly application-dependent sensor networks. Developers build sensor networks to collect and analyze low-level data from an environment of interest. Accomplishing the network's goal often depends on local cooperation, aggregation, or data processing because individual nodes have limited capabilities. Physically small, nodes have tiny or irreplaceable power reserves, communicate wirelessly, and may not possess unique identifiers. Further, they must form ad hoc relationships in a dense network with little or no preexisting infrastructure.Protocols and algorithms operating in the network must support large-scale distribution, often with only localized interactions among nodes. The network must continue operating even after significant node failure, and it must meet real-time requirements. In addition to the limitations imposed by applicationdependent deadlines, because it reflects a changing environment, the data the network gathers may intrinsically be valid for only a short time.Sensor networks may be deployed in a host of different environments, and they often figure into military scenarios. These networks may gather intelligence in battlefield conditions, track enemy troop movements, monitor a secured zone for activity, or measure damage and casualties. An airplane or artillery 1 could deploy these networks to otherwise unreachable regions.Although military applications may be the easiest to imagine, much broader opportunities await. Sensor networks could form an impromptu communications network for rescue personnel at disaster sites, or they could themselves help locate casualties. They could monitor conditions at the rim of a volcano, along an earthquake fault, or ...

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Improving the quality of healthcare and the prospects of "aging in place" using wireless sensor technology requires solving difficult problems in scale, energy management, data access, security, and privacy. We present AlarmNet, a novel system for assisted-living and residential monitoring that uses a two-way flow of data and analysis between the front and back-ends to enable context-aware protocols that are tailored to residents' individual patterns of living.AlarmNet integrates environmental, physiological, and activity sensors in a scalable, heterogeneous architecture.The SenQ query protocol provides real-time access to data and lightweight in-network processing. Circadian Activity Rhythm (CAR) analysis learns resident activity patterns and feeds them back into the network to aid context-aware power management and dynamic privacy policies.

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Jamming is a very effective denial-of-service attack that renders most higher-layer security mechanisms moot-yet it is often ignored in WSN design. We show that an interrupt jamming attack is simple to perpetrate in software using a MICAz mote, is energy efficient and stealthy for the jammer, and completely disrupts communication. Solutions are needed to mitigate this insider threat even if more powerful attackers are not thwarted.We present DEEJAM, a novel MAC-layer protocol for defeating stealthy jammers with IEEE 802.15.4-based hardware, to address this problematic area. It layers four defensive mechanisms to hide communication from a jammer, evade its search, and reduce its impact.Given the difficulty of modeling the physical layer accurately in simulation, we evaluate DEEJAM instead on the MICAz mote. We show the performance of the protocol against successively more complex attacks: interrupt jamming, activity jamming, scan jamming, and pulse jamming. Results show that DEEJAM defeats the otherwise devastating interrupt jammer, and achieves a packet delivery ratio of 88% in the presence of a pulse jammer.To the best of our knowledge, this work is the first to confront multiple types of jamming on common WSN hardware with solutions that are shown empirically to enable continued communication despite an ongoing attack.