Due to the wide spread of android smartphones, different types of attacks have emerged against android systems and accordingly many researches have been accomplished in the android security. In particular, a variety of covert channels have been recently developed in android systems. They are usually built up by utilizing physical media and distinct characteristics of systems in the literature. To the best of our information, however, we do not find out any research work establishing covert channels in android systems on basis of the sequential analysis, which is a kind of statistical decision theory. This is mainly because the sequential analysis has been conventionally treated as defense technique in terms of security. In contrast to this common application of the sequential analysis, we discover a new covert channel based on the sequential analysis in android systems. The key idea of newly devised covert channel is to harness the sequential analysis in order to encode (resp. decode) private information bits to (resp. from) multiple sequences of randomly selected data. Through simulation, we demonstrate that our developed covert channel works efficiently and thus it could be substantial threat to android systems.

Due to the unattended nature of wireless sensor networks, an adversary can physically capture and compromise sensor nodes and then mount a variety of attacks with the compromised nodes. To minimize the damage incurred by the compromised nodes, the system should detect and revoke them as soon as possible. To meet this need, researchers have recently proposed a variety of node compromise detection schemes in wireless ad hoc and sensor networks. For example, reputation-based trust management schemes identify malicious nodes but do not revoke them due to the risk of false positives. Similarly, software-attestation schemes detect the subverted software modules of compromised nodes. However, they require each sensor node to be attested periodically, thus incurring substantial overhead. To mitigate the limitations of the existing schemes, we propose a zone-based node compromise detection and revocation scheme in wireless sensor networks. The main idea behind our scheme is to use sequential hypothesis testing to detect suspect regions in which compromised nodes are likely placed. In these suspect regions, the network operator performs software attestation against sensor nodes, leading to the detection and revocation of the compromised nodes. Through quantitative analysis and simulation experiments, we show that the proposed scheme detects the compromised nodes with a small number of samples while reducing false positive and negative rates, even if a substantial fraction of the nodes in the zone are compromised. Additionally, we model the detection problem using a game theoretic analysis, derive the optimal strategies for the attacker and the defender, and show that the attacker's gain from node compromise is greatly limited by the defender when both the attacker and the defender follow their optimal strategies.

Due to the unattended nature of wireless sensor networks, an adversary can capture and compromise sensor nodes, make replicas of them, and then mount a variety of attacks with these replicas. These replica node attacks are dangerous because they allow the attacker to leverage the compromise of a few nodes to exert control over much of the network. Several replica node detection schemes have been proposed in the literature to defend against such attacks in static sensor networks. However, these schemes rely on fixed sensor locations and hence do not work in mobile sensor networks, where sensors are expected to move. In this work, we propose a fast and effective mobile replica node detection scheme using the Sequential Probability Ratio Test. To the best of our knowledge, this is the first work to tackle the problem of replica node attacks in mobile sensor networks. We show analytically and through simulation experiments that our scheme detects mobile replicas in an efficient and robust manner at the cost of reasonable overheads.

Due to the unattended nature of wireless sensor networks, an adversary can capture and compromise sensor nodes, generate their replicas, and thus mount a variety of attacks with these replicas. Such attacks are dangerous because they allow the attacker to leverage the compromise of a few nodes to exert control over much of the network. Several replica node detection schemes have been proposed in the literature to defend against such attacks in static sensor networks. However, these schemes rely on fixed sensor locations and hence do not work in mobile sensor networks, where sensors are expected to move. In this work, we propose a fast and effective mobile replica node detection scheme using the Sequential Probability Ratio Test. To the best of our knowledge, this is the first work to tackle the problem of replica node attacks in mobile sensor networks. We show analytically and through simulation experiments that our scheme provides effective and robust replica detection capability with reasonable overheads.

In this work, we propose a zone-based trust management scheme in wireless sensor networks in order to detect and revoke groups of compromised nodes by region. Our scheme works with less overhead than the existing trust management schemes since multiple compromised nodes in a zone can be detected and revoked at a time. We also present the possible attacks against our scheme and describe the countermeasures of these attacks.

Due to the unattended nature of wireless sensor networks, an adversary can physically capture and compromise sensor nodes and then mount a variety of attacks with these compromised nodes. To minimize the damage incurred by compromised nodes, the system should detect and revoke them as soon as possible. To meet this need, we propose a zone-based node compromise detection and revocation scheme in sensor networks. The main idea of the proposed scheme is to use the sequential hypothesis testing to detect suspect regions in which compromised nodes are likely placed. In these suspect regions, the network operator performs software attestation against sensor nodes, leading to the detection and revocation of the compromised nodes. Through analysis and simulation, we show that the proposed scheme provides effective and robust node compromise detection and revocation capability with little overhead.

Due to the unattended nature of wireless sensor networks, an adversary can capture and compromise sensor nodes, generate replicas of those compromised nodes, and mount a variety of attacks with the replicas he injects into the network. This is a severe type of attack in the sense that the attacker can leverage the compromise of a single node to create widespread effects on the network. In particular, we are interested in replica cluster attacks, in which many replicas with the same identity form a cluster in a small region. This is also a dangerous attack because attacker can leverage a replica cluster to harmfully impact on the much of the network. To defend against replica cluster attacks, we propose an efficient and effective replica cluster detection scheme using the sequential probability ratio test. We show analytically that our scheme achieves a high replica cluster detection capability.