Wireless networks are built upon a shared medium that makes it easy for adversaries to launch jamming-style attacks. These attacks can be easily accomplished by an adversary emitting radio frequency signals that do not follow an underlying MAC protocol. Jamming attacks can severely interfere with the normal operation of wireless networks and, consequently, mechanisms are needed that can cope with jamming attacks. In this paper, we examine radio interference attacks from both sides of the issue: first, we study the problem of conducting radio interference attacks on wireless networks, and second we examine the critical issue of diagnosing the presence of jamming attacks. Specifically, we propose 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

The proliferation of hotspots based on IEEE 802.11 wireless LANs brings the promise of seamless Internet access from a large number of public locations. However, as the number of users soars, so does the risk of possible misbehavior; to protect themselves, wireless ISPs already make use of a number of security mechanisms, and require mobile stations to authenticate themselves at the Access Points (APs). However, IEEE 802.11 works properly only if the stations also respect the MAC protocol. We show in this paper that a greedy user can substantially increase his share of bandwidth, at the expense of the other users, by slightly modifying the driver of his network adapter. We explain how easily this can be performed, in particular with the new generation of adapters. We then present DOMINO (System for Detection Of greedy behavior in the MAC layer of IEEE 802.11 public NetwOrks), a piece of software to be installed in the Access Point. DOMINO can detect and identify greedy stations, without requiring any modification of the standard protocol at the AP and without revealing its own presence. We illustrate these concepts by simulation results and by the description of our prototype.

Restricting network access of routing and packet forwarding to well-behaving nodes, and denying access from misbehaving nodes are critical for the proper functioning of a mobile ad-hoc network where cooperation among all networking nodes is usually assumed. However, the lack of a network infrastructure, the dynamics of the network topology and node membership, and the potential attacks from inside the network by malicious and/or non-cooperative selfish nodes make the conventional network access control mechanisms not applicable. We present URSA, a ubiquitous and robust access control solution for mobile ad-hoc networks. URSA implements ticket certification services through multiple-node consensus and fully localized instantiation, and uses tickets to identify and grant network access to well-behaving nodes. In URSA, no single node monopolizes the access decision or is completely trusted, and multiple nodes jointly monitor a local node and certify/revoke its ticket. Furthermore, URSA ticket certification services are fully localized into each node's neighborhood to ensure service ubiquity and resilience. Through analysis, simulations and experiments, we show that our design effectively enforces access control in the highly dynamic, mobile ad-hoc network.

Most proposed routing protocols for mobile ad hoc networks are vulnerable to modification, impersonation and fabrication attacks. The proposed secure rout8 Mobile Computing and Communications Review, Volume 6, Number 4 ing protocol, Authenticated Routing for Ad Hoc Networks, prevents such attacks through message authentication, integrity and non-repudiation. Simulation results show that ARAN maintains good network performance while offering significant security advantages over existing routing protocols.

In multihop wireless systems, such as ad-hoc and sensor networks, the need for cooperation among nodes to relay each other’s packets exposes them to a wide range of security attacks. A particularly devastating attack is known as the wormhole attack, where a malicious node records control and data traffic at one location and tunnels it to a colluding node, which replays it locally. This can have an adverse effect in route establishment by preventing nodes from discovering routes that are more than two hops away. In this paper, we present a lightweight countermeasure for the wormhole attack, called LITEWORP, which does not require specialized hardware. LITEWORP is particularly suitable for resource-constrained multihop wireless networks, such as sensor networks. Our solution allows detection of the wormhole, followed by isolation of the malicious nodes. Simulation results show that every wormhole is detected and isolated within a very short period of time over a large range of scenarios. The results also show that the fraction of packets lost due to the wormhole when LITEWORP is applied is negligible compared to the loss encountered when the method is not applied.

Abstract — CSMA/CA protocols rely on the random deferment of packet transmissions. Like most other protocols, CSMA/CA was designed with the assumption that the nodes would play by the rules. This can be dangerous, since the nodes themselves control their random deferment. Indeed, with the higher programmability of the network adapters, the temptation to tamper with the software or firmware is likely to grow; by doing so, a user could obtain a much larger share of the available bandwidth at the expense of other users. We use a game-theoretic approach to investigate the problem of the selfish behavior of nodes in CSMA/CA networks, specifically geared towards the most widely accepted protocol in this class of protocols, IEEE 802.11. We characterize two families of Nash equilibria in a single stage game, one of which always results in a network collapse. We argue that this result provides an incentive for cheaters to cooperate with each other. Explicit cooperation among nodes is clearly impractical. By applying the model of dynamic games borrowed from game theory, we derive the conditions for the stable and optimal functioning of a population of cheaters. We use this insight to develop a simple, localized and distributed protocol that successfully guides multiple selfish nodes to a Pareto-optimal Nash equilibrium. I.

Selfish behavior at the MAC layer can have devastating side effects on the performance of wireless networks, similar to the effects of DoS attacks. In this paper we focus on the prevention and detection of the manipulation of the backoff mechanism by selfish nodes in 802.11. We first propose an algorithm to ensure honest backoffs when at least one, either the receiver or the sender is honest. Then we discuss detection algorithms to deal with the problem of colluding selfish nodes. Although we have focused on the MAC layer of 802.11, our approach is general and can serve as a guideline for the design of any probabilistic distributed MAC protocol.

Wireless Medium Access Control (MAC) protocols such as IEEE 802.11 use distributed contention resolution mechanisms for sharing the wireless channel. In this environment, selfish hosts that fail to adhere to the MAC protocol may obtain an unfair throughput share. For example, IEEE 802.11 requires hosts competing for access to the channel to wait for a “backoff ” interval, randomly selected from a specified range, before initiating a transmission. Selfish hosts may wait for smaller backoff intervals than well-behaved hosts, thereby obtaining an unfair advantage. We present modifications to the IEEE 802.11 protocol to simplify detection of such selfish hosts, and analyze the optimality of the chosen strategy. We also present a penalty scheme for punishing selfish misbehavior. We develop two misbehavior models to capture the behavior of misbehaving hosts. Simulation results under these misbehavior models indicate that our detection and penalty schemes are successful in handling MAC layer misbehavior.

Abstract. In this paper we investigate the problem of maintaining connectivity under jamming in multihop ad hoc wireless networks. Connectivity is measured using a connectivity index, which indicates the probability that there exists a path between two nodes. We first show that connectivity can be drastically reduced with a relatively small number of jammers. We show that using sectored antennas can maintain connectivity in the presence of a significantly higher number of jammers at the expense of higher average number of hops. Finally, we show that mobility allows further resiliency to jamming. 1

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