One of the key advantages of Federated Learning (FL) is its ability to collaboratively train a Machine Learning (ML) model while keeping clients' data on-site. However, this can create a false sense of security. Despite not sharing private data increases the overall privacy, prior studies have shown that gradients exchanged during the FL training remain vulnerable to Gradient Inversion Attacks (GIAs). These attacks allow reconstructing the clients' local data, breaking the privacy promise of FL. GIAs can be launched by either a passive or an active server. In the latter case, a malicious server manipulates the global model to facilitate data reconstruction. While effective, earlier attacks falling under this category have been demonstrated to be detectable by clients, limiting their real-world applicability. Recently, novel active GIAs have emerged, claiming to be far stealthier than previous approaches. This work provides the first comprehensive analysis of these claims, investigating four state-of-the-art GIAs. We propose novel lightweight client-side detection techniques, based on statistically improbable weight structures and anomalous loss and gradient dynamics. Extensive evaluation across several configurations demonstrates that our methods enable clients to effectively detect active GIAs without any modifications to the FL training protocol.

Automatic fish detection in images plays a crucial role in marine biodiversity monitoring and environmental conservation. The advent of deep learning has significantly improved the results achievable in fish detection; however, underwater challenges such as scale variability, optical distortions, and color inconsistencies reveal some limitations of conventional deep learning-based detectors. To address these issues, we propose an improved fish detection model designed for underwater environments trained to perform joint underwater image enhancement and multi-scale fish detection. While incorporating structural enhancements for multi-scale robustness, such as a dedicated tiny object detection head and attention mechanisms, the core of our approach resides in the joint training of an underwater image enhancement module with the detector. We evaluate our method on two challenging test sets. The experimental results demonstrate that our model significantly outperforms state-of-the-art methods, achieving an average precision between 0.84 and 0.89. Despite its superior accuracy, the proposed solution maintains a lightweight architecture with only 24 millions of parameters and ensures real-time processing capabilities (13 frames per second on edge hardware), highlighting its potential for effective deployment in marine research and autonomous fisheries monitoring. • YOLO-JUICE boosts small-object detection with an extra tiny-object head. • YOLO-JUICE preserves details without extra cost with a space to depth module. • YOLO-JUICE refines spatial and channel features with a spatial-channel attention. • YOLO-JUICE is jointly trained for image classification and enhancement.

Internet of Things (IoT) devices are increasingly permeating homes, industries, and many other environments. The need for robust security measures in IoT networks has never been more critical, since they are becoming the preferred target for cyberattacks. In this paper, we address the challenge of detecting abnormal communication patterns in IoT networks using Graph Neural Networks (GNNs). To this end, we have conducted a comprehensive and fair comparison of machine learning approaches and GNNs, for both static and dynamic graphs, across three recent datasets, IoT23, IoTID20, IoT Traces, that contain recordings of network communications among IoT devices in real environments. Differently from the state-of-the-art, we face the problem as a node anomaly detection task under the realistic assumption of only having normal traffic samples for training the GNNs. Furthermore, we have also restricted the false positive rate below 1% to make the system practical for human operators willing to use it as an Anomaly-based IDS (A-IDS). Finally, the experimental results highlight the relevance of structural information to effectively address the task in real-world conditions. • The security of IoT devices is becoming a relevant issue in modern networks. • Host-based analysis is unfeasible in many IoT devices. • Graph Neural Networks are becoming a promising tool for network traffic analysis. • Anomaly detection is the most suitable approach scenarios where attacks are unknow. • A comparison among ML methods and GNNs for anomaly detection is proposed.

Sharing facial pictures through online services, especially on social networks, has become a common habit for thousands of users. This practice hides a possible threat to privacy: the owners of such services, as well as malicious users, could automatically extract information from faces using modern and effective neural networks. In this article, we propose the harmless use of adversarial attacks, i.e., variations of images that are almost imperceptible to the human eye and that are typically generated with the malicious purpose to mislead Convolutional Neural Networks (CNNs). Such attacks have been instead adopted to (1) obfuscate soft biometrics (gender, age, ethnicity) but (2) without degrading the quality of the face images posted online. We achieve the above-mentioned two conflicting goals by modifying the implementations of four of the most popular adversarial attacks, namely FGSM, PGD, DeepFool, and C&W, in order to constrain the average amount of noise they generate on the image and the maximum perturbation they add on the single pixel. We demonstrate, in an experimental framework including three popular CNNs, namely VGG16, SENet, and MobileNetV3, that the considered obfuscation method, which requires at most 4 seconds for each image, is effective not only when we have a complete knowledge of the neural network that extracts the soft biometrics (white box attacks) but also when the adversarial attacks are generated in a more realistic black box scenario. Finally, we prove that an opponent can implement defense techniques to partially reduce the effect of the obfuscation, but substantially paying in terms of accuracy over clean images; this result, confirmed by the experiments carried out with three popular defense methods, namely adversarial training, denoising autoencoder, and Kullback-Leibler autoencoder, shows that it is not convenient for the opponent to defend himself and that the proposed approach is robust to defenses.

Face analysis includes a variety of specific problems as face detection, person identification, gender and ethnicity recognition, just to name the most common ones; in the last two decades, significant research efforts have been devoted to the challenging task of age estimation from faces, as witnessed by the high number of published papers. The explosion of the deep learning paradigm, that is determining a spectacular increasing of the performance, is in the public eye; consequently, the number of approaches based on deep learning is impressively growing and this also happened for age estimation. The exciting results obtained have been recently surveyed on almost all the specific face analysis problems; the only exception stands for age estimation, whose last survey dates back to 2010 and does not include any deep learning based approach to the problem. This paper provides an analysis of the deep methods proposed in the last six years; these are analysed from different points of view: the network architecture together with the learning procedure, the used datasets, data preprocessing and augmentation, and the exploitation of additional data coming from gender, race and face expression. The review is completed by discussing the results obtained on public datasets, so as the impact of different aspects on system performance, together with still open issues.

Graph matching is essential in several fields that use structured information, such as biology, chemistry, social networks, knowledge management, document analysis and others. Except for special classes of graphs, graph matching has in the worst-case an exponential complexity; however, there are algorithms that show an acceptable execution time, as long as the graphs are not too large and not too dense. In this paper we introduce a novel subgraph isomorphism algorithm, VF3, particularly efficient in the challenging case of graphs with thousands of nodes and a high edge density. Its performance, both in terms of time and memory, has been assessed on a large dataset of 12,700 random graphs with a size up to 10,000 nodes, made publicly available. VF3 has been compared with four other state-of-the-art algorithms, and the huge experimentation required more than two years of processing time. The results confirm that VF3 definitely outperforms the other algorithms when the graphs become huge and dense, but also has a very good performance on smaller or sparser graphs.

The detection of persons from videos is particularly important in many computer vision contexts being an enabling technology for several relevant applications either for security and safety or for business intelligence purposes. The adoption of a depth sensor mounted in a top-view position is often used to achieve high person detection accuracy as it allows to cope effectively with occlusions and difficult lighting conditions. In this paper, we propose a new method for people detection from depth maps produced by sensors mounted in a zenithal position. The method is designed with the aim of providing an optimal trade off between the detection accuracy and the computational complexity. The proposed approach adopts a dynamic background modeling strategy in order to find the objects of interest into the scene; then a lightweight algorithm is used to filter out the noise from the foreground image and to determine the position of the persons into the scene. The experimental analysis carried out on a public and large dataset allowed to demonstrate that the method is fast and accurate. The method has been compared with respect to two different approaches available in the literature for people detection from a depth camera mounted in a zenithal position: an unsupervised method that is fast although not highly accurate, and a supervised one that conversely is very accurate but less computationally efficient. The proposed method allows to achieve comparable accuracy of the supervised approach using very few computational resources, with a reduction of an order of magnitude of the processing times.

The detection of illegal roadside parking is becoming more and more interesting in the field of intelligent transportation systems, since it may cause traffic congestion or accidents. In this paper we propose a method able to analyze videos acquired by traditional surveillance cameras and to automatically detect the vehicles stopped in a forbidden area. Two main contributions have been introduced: first, spatio temporal information related to the stopped vehicles are encoded by a heat map; second, the background is not updated by evaluating the movement of the vehicle in a single time instant, but instead the whole movement of the vehicles, encoded into the heat map, is taken into account. Two widely adopted datasets, namely the iLids and the PETS 2000, have been used to experimentally evaluate the proposed approach and the results achieved, compared with state of the art methodologies, confirm its effectiveness.

In this paper we propose a novel approach for the audio-based detection of events. The approach adopts the bag of words paradigm, and has two main advantages over other techniques present in the literature: the ability to automatically adapt (through a learning phase) to both short, impulsive sounds and long, sustained ones, and the ability to work in noisy environments where the sounds of interest are superimposed to background sounds possibly having similar characteristics. The proposed method has been experimentally validated on a large database of sounds, including several kinds of background noise, which are superimposed to the sounds to be recognized. The obtained performance has been compared with the results of another audio event detection algorithm from the literature, showing a significant improvement.