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Federated learning (FL) enables participants to collaboratively train machine and deep learning models while safeguarding data privacy. However, the FL paradigm still has drawbacks that affect its trustworthiness, as malicious participants could launch adversarial attacks against the training process. Previous research has examined the robustness of horizontal FL scenarios under various attacks. However, there is a lack of research evaluating the robustness of decentralized vertical FL and comparing it with horizontal FL architectures affected by adversarial attacks. Therefore, this study proposes three decentralized FL architectures: HoriChain, VertiChain, and VertiComb. These architectures feature different neural networks and training protocols suitable for horizontal and vertical scenarios. Subsequently, a decentralized, privacy-preserving, and federated use case with non-IID data to classify handwritten digits is deployed to assess the performance of the three architectures. Finally, a series of experiments computes and compares the robustness of the proposed architectures when they are affected by different data poisoning methods, including image watermarks and gradient poisoning adversarial attacks. The experiments demonstrate that while specific configurations of both attacks can undermine the classification performance of the architectures, HoriChain is the most robust one. [ABSTRACT FROM AUTHOR]

Detecting malicious attacks presents a major challenge in the field of reinforcement learning (RL), as such attacks can force the victim to perform abnormal actions, with potentially severe consequences. To mitigate these risks, current research focuses on the enhancement of RL algorithms with efficient detection mechanisms, especially for real-world applications. Adversarial attacks have the potential to alter the environmental dynamics of a Markov Decision Process (MDP) perceived by an RL agent. Leveraging these changes in dynamics, we propose a novel approach to detect attacks. Our contribution can be summarized in two main aspects. Firstly, we propose a novel formalization of the attack detection problem that entails analyzing modifications made by attacks to the transition and reward dynamics within the environment. This problem can be framed as a context change detection problem, where the goal is to identify the transition from a "free-of-attack" situation to an "under-attack" scenario. To solve this problem, we propose a groundbreaking "model-free" clustering-based countermeasure. This approach consists of two essential steps: first, partitioning the transition space into clusters, and then using this partitioning to identify changes in environmental dynamics caused by adversarial attacks. To assess the efficiency of our detection method, we performed experiments on four established RL domains (grid-world, mountain car, carpole, and acrobot) and subjected them to four advanced attack types. Uniform, Strategically-timed, Q-value, and Multi-objective. Our study proves that our technique has a high potential for perturbation detection, even in scenarios where attackers employ more sophisticated strategies. [ABSTRACT FROM AUTHOR]

Progress in making neural networks more robust against adversarial attacks is mostly marginal, despite the great efforts of the research community. Moreover, the robustness evaluation is often imprecise, making it challenging to identify promising approaches. We do an observational study on the classification decisions of 19 different state-of-the-art neural networks trained to be robust against adversarial attacks. This analysis gives a new indication of the limits of the robustness of current models on a common benchmark. In addition, our findings suggest that current untargeted adversarial attacks induce misclassification toward only a limited amount of different classes. Similarly, we find that previous attacks under-explore the perturbation space during optimization. This leads to unsuccessful attacks for samples where the initial gradient direction is not a good approximation of the final adversarial perturbation direction. Additionally, we observe that both over- and under-confidence in model predictions result in an inaccurate assessment of model robustness. Based on these observations, we propose a novel loss function for adversarial attacks that consistently improves their efficiency and success rate compared to prior attacks for all 30 analyzed models. [ABSTRACT FROM AUTHOR]

Deep neural networks (DNNs) are vulnerable to adversarial examples that are similar to original samples but contain the perturbations intentionally crafted by adversaries. Many efficient and typical attacks are based on the fast gradient sign method and usually against models by adding invariant perturbation magnitude to the input of DNN in each iteration. Some studies report that the loss surface demonstrates significant non-smooth variation in the input space. The invariant perturbation size may not be conducive to finding adversarial examples fast in iterations. In this work, we propose the adaptive moment iterative fast gradient sign method (Adam-FGSM), a new iterative white-box attack. According to the moment estimations of the gradients, Adam-FGSM can follow stable perturbation directions by the first-order moment estimation of gradients and adaptively compute the perturbation size with the second-order moment estimations. The experimental results show that Adam-FGSM could adopt rugged input loss space to generate adversarial examples with a higher attack success rate and acceptable transferability in fewer iterations. We analyze the attack process of Adam-FGSM to explain why it can achieve outstanding performance by visualizing the L1, L ∞ norms, and the cosine similarity of perturbations. Furthermore, we plot trajectories of iterative attack methods to observe the geometric characteristics intuitively. [ABSTRACT FROM AUTHOR]

Security-sensitive applications that rely on Deep Neural Networks (DNNs) are vulnerable to small perturbations that are crafted to generate Adversarial Examples. The (AEs) are imperceptible to humans and cause DNN to misclassify them. Many defense and detection techniques have been proposed. Model's confidences and Dropout, as a popular way to estimate the model's uncertainty, have been used for AE detection but they showed limited success against black- and gray-box attacks. Moreover, the state-of-the-art detection techniques have been designed for specific attacks or broken by others, need knowledge about the attacks, are not consistent, increase model parameters overhead, are time-consuming, or have latency in inference time. To trade off these factors, we revisit the model's uncertainty and confidences and propose a novel unsupervised ensemble AE detection mechanism that 1) uses the uncertainty method called SelectiveNet, 2) processes model layers outputs, i.e. feature maps, to generate new confidence probabilities. The detection method is called SFAD. Experimental results show that the proposed approach achieves better performance against black- and gray-box attacks than the state-of-the-art methods and achieves comparable performance against white-box attacks. Moreover, results show that SFAD is fully robust against High Confidence Attacks (HCAs) for MNIST and partially robust for CIFAR10 datasets.1 [ABSTRACT FROM AUTHOR]

Visual speech recognition is essential in understanding speech in several real-world applications such as surveillance systems and aiding differently-abled. It proliferates the research in the realm of visual speech recognition, also known as Automatic Lip Reading (ALR). In recent years, Deep Learning (DL) methods are being utilised for developing ALR systems. DL models tend to be vulnerable to adversarial attacks. Studying these attacks creates new research directions in designing robust DL systems. Existing attacks on images and videos classification models are not directly applicable to ALR systems. Since the ALR systems encompass temporal information, attacking these systems is comparatively more challenging and strenuous than attacking image classification models. Similarly, compared to other video classification tasks, the region-of-interest is smaller in the case of ALR systems. Despite these factors, our proposed method, Fooling AuTomAtic Lip Reading (FATALRead), can successfully perform adversarial attacks on state-of-the-art ALR systems. To the best of our knowledge, we are the first to successfully fool ALR systems for the word recognition task. We further demonstrate that the success of the attack is increased by incorporating logits instead of probabilities in the loss function. Our extensive experiments on a publicly available dataset, show that our attack successfully circumvents the well-known transformation based defences. [ABSTRACT FROM AUTHOR]