SCADA Secure Wireless Networks
Recent advances in wireless communications and digital electronics have enabled rapid development of a variety of wireless network technologies, such as wireless LANs, home networks, multi-hop ad hoc networks, and sensor networks. Wireless networks are vulnerable to radio jamming attacks because of the open and shared nature of wireless medium. In a jamming attack, an attacker injects a high level of noise into the wireless system, significantly reducing the signal-to-noise ratio (SINR) and reducing the probability of successful message receptions. Even though the spread spectrum technologies have raised the bar for the jamming defenses, they cannot deal with insider jammers who launch stealthy and intelligent jamming attacks from compromised nodes. To cope with such dangerous insiders, the first and most important step is to identify them. In this activity, we considered the problem of identifying the insider jammers. Our approach is unique: we exploit the half-duplex nature of the attackers. Specifically, a half-duplex jammer has the following characteristics: because of a non-negligible channel switching time, it cannot send or receive on two different channels simultaneously, and because of a non-negligible transmit-to-receive switching time, it cannot send and receive on a channel simultaneously. Therefore, when a compromised node jams, it cannot either send or receive any other packets. More importantly, if an honest node is observed doing a send or receive action at the time of the jammed packet, it can arguably prove that it cannot be the cause of the jammed packet. In other words, the honest node obtains an “alibi.” In the context of jamming attacks, an alibi for a node is a proof showing that an honest node could not have committed a jamming action at a specific time because it was witnessed doing a legitimate action at the same time. We explored the alibi framework in dealing with insider jammers. We studied various properties of the framework, including detection accuracy, detection time, network availability, and necessary conditions for the alibi framework to work. We also investigated different designs of the alibi framework, such as sending-based alibis and receiving-based alibis, and studied their strengths and weaknesses. We evaluated the alibi framework through analysis, simulations, and MICAz experiments.
