SSAP: A Shape-Sensitive Adversarial Patch for Comprehensive Disruption of Monocular Depth Estimation in Autonomous Navigation Applications

Monocular depth estimation (MDE) has advanced significantly, primarily through the integration of convolutional neural networks (CNNs) and more recently, Transformers. However, concerns about their susceptibility to adversarial attacks have emerged, especially in safety-critical domains like autonomous driving and robotic navigation. Existing approaches for assessing CNN-based depth prediction methods have fallen short in inducing comprehensive disruptions to the vision system, often limited to specific local areas. In this paper, we introduce SSAP (Shape-Sensitive Adversarial Patch), a novel approach designed to comprehensively disrupt monocular depth estimation (MDE) in autonomous navigation applications. Our patch is crafted to selectively undermine MDE in two distinct ways: by distorting estimated distances or by creating the illusion of an object disappearing from the system's perspective. Notably, our patch is shape-sensitive, meaning it considers the specific shape and scale of the target object, thereby extending its influence beyond immediate proximity. Furthermore, our patch is trained to effectively address different scales and distances from the camera. Experimental results demonstrate that our approach induces a mean depth estimation error surpassing 0.5, impacting up to 99% of the targeted region for CNN-based MDE models. Additionally, we investigate the vulnerability of Transformer-based MDE models to patch-based attacks, revealing that SSAP yields a significant error of 0.59 and exerts substantial influence over 99% of the target region on these models.

Anomaly Unveiled: Securing Image Classification against Adversarial Patch Attacks

Adversarial patch attacks pose a significant threat to the practical deployment of deep learning systems. However, existing research primarily focuses on image pre-processing defenses, which often result in reduced classification accuracy for clean images and fail to effectively counter physically feasible attacks. In this paper, we investigate the behavior of adversarial patches as anomalies within the distribution of image information and leverage this insight to develop a robust defense strategy. Our proposed defense mechanism utilizes a clustering-based technique called DBSCAN to isolate anomalous image segments, which is carried out by a three-stage pipeline consisting of Segmenting, Isolating, and Blocking phases to identify and mitigate adversarial noise. Upon identifying adversarial components, we neutralize them by replacing them with the mean pixel value, surpassing alternative replacement options. Our model-agnostic defense mechanism is evaluated across multiple models and datasets, demonstrating its effectiveness in countering various adversarial patch attacks in image classification tasks. Our proposed approach significantly improves accuracy, increasing from 38.8\% without the defense to 67.1\% with the defense against LaVAN and GoogleAp attacks, surpassing prominent state-of-the-art methods such as LGS (53.86\%) and Jujutsu (60\%)

ODDR: Outlier Detection & Dimension Reduction Based Defense Against Adversarial Patches

Adversarial attacks are a major deterrent towards the reliable use of machine learning models. A powerful type of adversarial attacks is the patch-based attack, wherein the adversarial perturbations modify localized patches or specific areas within the images to deceive the trained machine learning model. In this paper, we introduce Outlier Detection and Dimension Reduction (ODDR), a holistic defense mechanism designed to effectively mitigate patch-based adversarial attacks. In our approach, we posit that input features corresponding to adversarial patches, whether naturalistic or otherwise, deviate from the inherent distribution of the remaining image sample and can be identified as outliers or anomalies. ODDR employs a three-stage pipeline: Fragmentation, Segregation, and Neutralization, providing a model-agnostic solution applicable to both image classification and object detection tasks. The Fragmentation stage parses the samples into chunks for the subsequent Segregation process. Here, outlier detection techniques identify and segregate the anomalous features associated with adversarial perturbations. The Neutralization stage utilizes dimension reduction methods on the outliers to mitigate the impact of adversarial perturbations without sacrificing pertinent information necessary for the machine learning task. Extensive testing on benchmark datasets and state-of-the-art adversarial patches demonstrates the effectiveness of ODDR. Results indicate robust accuracies matching and lying within a small range of clean accuracies (1%-3% for classification and 3%-5% for object detection), with only a marginal compromise of 1%-2% in performance on clean samples, thereby significantly outperforming other defenses.

Physical Adversarial Attacks For Camera-based Smart Systems: Current Trends, Categorization, Applications, Research Challenges, and Future Outlook

In this paper, we present a comprehensive survey of the current trends focusing specifically on physical adversarial attacks. We aim to provide a thorough understanding of the concept of physical adversarial attacks, analyzing their key characteristics and distinguishing features. Furthermore, we explore the specific requirements and challenges associated with executing attacks in the physical world. Our article delves into various physical adversarial attack methods, categorized according to their target tasks in different applications, including classification, detection, face recognition, semantic segmentation and depth estimation. We assess the performance of these attack methods in terms of their effectiveness, stealthiness, and robustness. We examine how each technique strives to ensure the successful manipulation of DNNs while mitigating the risk of detection and withstanding real-world distortions. Lastly, we discuss the current challenges and outline potential future research directions in the field of physical adversarial attacks. We highlight the need for enhanced defense mechanisms, the exploration of novel attack strategies, the evaluation of attacks in different application domains, and the establishment of standardized benchmarks and evaluation criteria for physical adversarial attacks. Through this comprehensive survey, we aim to provide a valuable resource for researchers, practitioners, and policymakers to gain a holistic understanding of physical adversarial attacks in computer vision and facilitate the development of robust and secure DNN-based systems.

SAAM: Stealthy Adversarial Attack on Monoculor Depth Estimation

In this paper, we investigate the vulnerability of MDE to adversarial patches. We propose a novel \underline{S}tealthy \underline{A}dversarial \underline{A}ttacks on \underline{M}DE (SAAM) that compromises MDE by either corrupting the estimated distance or causing an object to seamlessly blend into its surroundings. Our experiments, demonstrate that the designed stealthy patch successfully causes a DNN-based MDE to misestimate the depth of objects. In fact, our proposed adversarial patch achieves a significant 60\% depth error with 99\% ratio of the affected region. Importantly, despite its adversarial nature, the patch maintains a naturalistic appearance, making it inconspicuous to human observers. We believe that this work sheds light on the threat of adversarial attacks in the context of MDE on edge devices. We hope it raises awareness within the community about the potential real-life harm of such attacks and encourages further research into developing more robust and adaptive defense mechanisms.

DAP: A Dynamic Adversarial Patch for Evading Person Detectors

In this paper, we present a novel approach for generating naturalistic adversarial patches without using GANs. Our proposed approach generates a Dynamic Adversarial Patch (DAP) that looks naturalistic while maintaining high attack efficiency and robustness in real-world scenarios. To achieve this, we redefine the optimization problem by introducing a new objective function, where a similarity metric is used to construct a similarity loss. This guides the patch to follow predefined patterns while maximizing the victim model's loss function. Our technique is based on directly modifying the pixel values in the patch which gives higher flexibility and larger space to incorporate multiple transformations compared to the GAN-based techniques. Furthermore, most clothing-based physical attacks assume static objects and ignore the possible transformations caused by non-rigid deformation due to changes in a person's pose. To address this limitation, we incorporate a ``Creases Transformation'' (CT) block, i.e., a preprocessing block following an Expectation Over Transformation (EOT) block used to generate a large variation of transformed patches incorporated in the training process to increase its robustness to different possible real-world distortions (e.g., creases in the clothing, rotation, re-scaling, random noise, brightness and contrast variations, etc.). We demonstrate that the presence of different real-world variations in clothing and object poses (i.e., above-mentioned distortions) lead to a drop in the performance of state-of-the-art attacks. For instance, these techniques can merely achieve 20\% in the physical world and 30.8\% in the digital world while our attack provides superior success rate of up to 65\% and 84.56\%, respectively when attacking the YOLOv3tiny detector deployed in smart cameras at the edge.

Exploring Machine Learning Privacy/Utility trade-off from a hyperparameters Lens

Machine Learning (ML) architectures have been applied to several applications that involve sensitive data, where a guarantee of users' data privacy is required. Differentially Private Stochastic Gradient Descent (DPSGD) is the state-of-the-art method to train privacy-preserving models. However, DPSGD comes at a considerable accuracy loss leading to sub-optimal privacy/utility trade-offs. Towards investigating new ground for better privacy-utility trade-off, this work questions; (i) if models' hyperparameters have any inherent impact on ML models' privacy-preserving properties, and (ii) if models' hyperparameters have any impact on the privacy/utility trade-off of differentially private models. We propose a comprehensive design space exploration of different hyperparameters such as the choice of activation functions, the learning rate and the use of batch normalization. Interestingly, we found that utility can be improved by using Bounded RELU as activation functions with the same privacy-preserving characteristics. With a drop-in replacement of the activation function, we achieve new state-of-the-art accuracy on MNIST (96.02\%), FashionMnist (84.76\%), and CIFAR-10 (44.42\%) without any modification of the learning procedure fundamentals of DPSGD.

AdvART: Adversarial Art for Camouflaged Object Detection Attacks

A majority of existing physical attacks in the real world result in conspicuous and eye-catching patterns for generated patches, which made them identifiable/detectable by humans. To overcome this limitation, recent work has proposed several approaches that aim at generating naturalistic patches using generative adversarial networks (GANs), which may not catch human's attention. However, these approaches are computationally intensive and do not always converge to natural looking patterns. In this paper, we propose a novel lightweight framework that systematically generates naturalistic adversarial patches without using GANs. To illustrate the proposed approach, we generate adversarial art (AdvART), which are patches generated to look like artistic paintings while maintaining high attack efficiency. In fact, we redefine the optimization problem by introducing a new similarity objective. Specifically, we leverage similarity metrics to construct a similarity loss that is added to the optimized objective function. This component guides the patch to follow a predefined artistic patterns while maximizing the victim model's loss function. Our patch achieves high success rates with $12.53\%$ mean average precision (mAP) on YOLOv4tiny for INRIA dataset.

APARATE: Adaptive Adversarial Patch for CNN-based Monocular Depth Estimation for Autonomous Navigation

In recent years, monocular depth estimation (MDE) has witnessed a substantial performance improvement due to convolutional neural networks (CNNs). However, CNNs are vulnerable to adversarial attacks, which pose serious concerns for safety-critical and security-sensitive systems. Specifically, adversarial attacks can have catastrophic impact on MDE given its importance for scene understanding in applications like autonomous driving and robotic navigation. To physically assess the vulnerability of CNN-based depth prediction methods, recent work tries to design adversarial patches against MDE. However, these methods are not powerful enough to fully fool the vision system in a systemically threatening manner. In fact, their impact is partial and locally limited; they mislead the depth prediction of only the overlapping region with the input image regardless of the target object size, shape and location. In this paper, we investigate MDE vulnerability to adversarial patches in a more comprehensive manner. We propose a novel adaptive adversarial patch (APARATE) that is able to selectively jeopardize MDE by either corrupting the estimated distance, or simply manifesting an object as disappeared for the autonomous system. Specifically, APARATE is optimized to be shape and scale-aware, and its impact adapts to the target object instead of being limited to the immediate neighborhood. Our proposed patch achieves more than $14~meters$ mean depth estimation error, with $99\%$ of the target region being affected. We believe this work highlights the threat of adversarial attacks in the context of MDE, and we hope it would alert the community to the real-life potential harm of this attack and motivate investigating more robust and adaptive defenses for autonomous robots.

AdvRain: Adversarial Raindrops to Attack Camera-based Smart Vision Systems

Vision-based perception modules are increasingly deployed in many applications, especially autonomous vehicles and intelligent robots. These modules are being used to acquire information about the surroundings and identify obstacles. Hence, accurate detection and classification are essential to reach appropriate decisions and take appropriate and safe actions at all times. Current studies have demonstrated that "printed adversarial attacks", known as physical adversarial attacks, can successfully mislead perception models such as object detectors and image classifiers. However, most of these physical attacks are based on noticeable and eye-catching patterns for generated perturbations making them identifiable/detectable by human eye or in test drives. In this paper, we propose a camera-based inconspicuous adversarial attack (\textbf{AdvRain}) capable of fooling camera-based perception systems over all objects of the same class. Unlike mask based fake-weather attacks that require access to the underlying computing hardware or image memory, our attack is based on emulating the effects of a natural weather condition (i.e., Raindrops) that can be printed on a translucent sticker, which is externally placed over the lens of a camera. To accomplish this, we provide an iterative process based on performing a random search aiming to identify critical positions to make sure that the performed transformation is adversarial for a target classifier. Our transformation is based on blurring predefined parts of the captured image corresponding to the areas covered by the raindrop. We achieve a drop in average model accuracy of more than $45\%$ and $40\%$ on VGG19 for ImageNet and Resnet34 for Caltech-101, respectively, using only $20$ raindrops.