Federated learning is a novel distributed learning framework, which enables thousands of participants to collaboratively construct a deep learning model. In order to protect confidentiality of the training data, the shared information between server and participants are only limited to model parameters. However, this setting is vulnerable to model poisoning attack, since the participants have permission to modify the model parameters. In this paper, we perform systematic investigation for such threats in federated learning and propose a novel optimization-based model poisoning attack. Different from existing methods, we primarily focus on the effectiveness, persistence and stealth of attacks. Numerical experiments demonstrate that the proposed method can not only achieve high attack success rate, but it is also stealthy enough to bypass two existing defense methods.

With the continuous development of computer hardware equipment and deep learning technology, it is easier for people to swap faces in videos by currently-emerging multimedia tampering tools, such as the most popular deepfake. It would bring a series of new threats of security. Although many forensic researches have focused on this new type of manipulation and achieved high detection accuracy, most of which are based on supervised learning mechanism with requiring a large number of labeled samples for training. In this paper, we first develop a novel unsupervised detection manner for identifying deepfake videos. The main fundamental behind our proposed method is that the face region in the real video is taken by the camera while its counterpart in the deepfake video is usually generated by the computer; the provenance of two videos is totally different. Specifically, our method includes two clustering stages based on Photo-Response Non-Uniformity (PRNU) and noiseprint feature. Firstly, the PRNU fingerprint of each video frame is extracted, which is used to cluster the full-size identical source video (regardless of its real or fake). Secondly, we extract the noiseprint from the face region of the video, which is used to identify (re-cluster for the task of binary classification) the deepfake sample in each cluster. Numerical experiments verify our proposed unsupervised method performs very well on our own dataset and the benchmark FF++ dataset. More importantly, its performance rivals that of the supervised-based state-of-the-art detectors.

This article investigates the secure and privacy-preserving consensus problem of multiagent systems (MASs) with directed interaction topologies under multiple cyberattacks, which contain deception attacks and DoS attacks. First, a unified attack model is introduced to characterize such a multiple attack phenomenon. Besides, considering the existence of eavesdroppers who can intercept the data transmitted on the links, a fully distributed agent value reconstruction method based on the idea of state decomposition is designed to prevent the leakage of the agent's initial information. Then, a novel privacy-preserving adaptive resilient consensus algorithm (PPARCA) with certain graph robustness condition for MASs under the multiple cyberattacks is proposed. The algorithm adaptively takes different countermeasures in the face of different cyberattacks. PPARCA uses the reconstructed agents' states and combines with the modified secure acceptance and broadcast algorithm (SABA). Theoretical analysis shows that the proposed algorithm can effectively protect the privacy of the initial state of the agents, and reach resilient consensus in the face of cyberattacks. Finally, numerical simulations and Raspberry Pi MASs practical application experiments demonstrate the effectiveness of the proposed results.

The problem of authenticating a re-sampled image has been investigated over many years. However, few current research proposes a statistical model-based test, resulting in that statistical performance of the re-sampling detector could not be completely analyzed. To fill the gap, we utilize a parametric model to expose traces of re-sampling forgery, which is described with the distribution of residual noise. Afterwards, we propose a statistical model describing the residual noise from a re-sampled image. Then the detection problem is cast into the framework of hypothesis testing theory. By considering the image content with designing texture weight map, two types of statistical detectors are established. In an ideal context in which all distribution parameters are perfectly known, the Likelihood Ratio Test (LRT) is presented and its performance is theoretically established. An upper bound of the detection power can be successfully obtained from statistical performance of LRT. For a practical use, when the distribution parameters are not known, a generalized LRT with three different maps based on estimation of parameters is established. Numerical results on simulated data and real natural images highlight the relevance of our proposed approach.

In this paper, a novel distributed algorithm derived from the event-triggered strategy is proposed for achieving resilient consensus of multi-agent networks (MANs) under deception attacks. These malicious deception attacks are intended to interfere with the communication channel causing periods in time at which the sending information among nodes is modified. In particular, we develop an event-triggered update rule which can mitigate the influence of the attackers and at the same time reduce the computing and communication consumption. Each node chooses the instances to update its state information by checking whether its neighbor set meets a given cardinality-dependent function or not. With specified prerequisite on the coupling weights and the sampling period, the consensus achievement of the MANs is independent of the deception attacks, but strictly depends on the robustness of the interconnection topology. Simulation examples are finally given to illustrate the efficacy of the theoretical results.

With the development of facial recognition technology, face anti-spoofing as the most important security module of face recognition system becomes more and more important. As a matter of fact, face anti-spoofing is still a challenging task, especially facing various attacks simultaneously. Moreover, most of current detectors mainly focus on binary classification while usually fail to complete the task of fine-grained multiple classification, referring to as replay, print, partial mask, and full mask attacks. To fill the gap, in this context, it is proposed to design the fine-grained detection network for classifying various face spoofing attack modes. First, we propose to establish a Transformer style network structure for feature extraction, where the convolution mapping operation is adopted instead of traditional linear mapping. Specifically, we adopt the self-attention module for extracting long distance feature, and convolution mapping is used to maintain the model's ability to extract local features. Finally, the simple yet effective linear classifier is introduced for fine-grained classification. Moreover, with the help of the VGG based style-transfer network, the well-designed scheme of data augmentation module is proposed for solving the problem of insufficient training samples. In the large-scale experiments, compared with the baseline detectors, our proposed fine-grained classifier with low computation cost performs its superiority for multiple classification.