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The dark web has emerged as the state-of-the-art solution for enhanced anonymity. Just like a double-edged sword, it also inadvertently becomes the safety net and breeding ground for illicit activities. Among them, cryptocurrencies have been prevalently abused to receive illicit income while evading regulations. Despite the continuing efforts to combat illicit activities, there is still a lack of an in-depth understanding regarding the characteristics and dynamics of cryptocurrency abuses on the dark web. In this work, we conduct a multi-dimensional and systematic study to track cryptocurrency-related illicit activities and campaigns on the dark web. We first harvest a dataset of 4,923 cryptocurrency-related onion sites with over 130K pages. Then, we detect and extract the illicit blockchain transactions to characterize the cryptocurrency abuses, targeting features from single/clustered addresses and illicit campaigns. Throughout our study, we have identified 2,564 illicit sites with 1,189 illicit blockchain addresses, which account for 90.8 BTC in revenue. Based on their inner connections, we further identify 66 campaigns behind them. Our exploration suggests that illicit activities on the dark web have strong correlations, which can guide us to identify new illicit blockchain addresses and onions, and raise alarms at the early stage of their deployment.

Vulnerability detectors based on deep learning (DL) models have proven their effectiveness in recent years. However, the shroud of opacity surrounding the decision-making process of these detectors makes it difficult for security analysts to comprehend. To address this, various explanation approaches have been proposed to explain the predictions by highlighting important features, which have been demonstrated effective in other domains such as computer vision and natural language processing. Unfortunately, an in-depth evaluation of vulnerability-critical features, such as fine-grained vulnerability-related code lines, learned and understood by these explanation approaches remains lacking. In this study, we first evaluate the performance of ten explanation approaches for vulnerability detectors based on graph and sequence representations, measured by two quantitative metrics including fidelity and vulnerability line coverage rate. Our results show that fidelity alone is not sufficient for evaluating these approaches, as fidelity incurs significant fluctuations across different datasets and detectors. We subsequently check the precision of the vulnerability-related code lines reported by the explanation approaches, and find poor accuracy in this task among all of them. This can be attributed to the inefficiency of explainers in selecting important features and the presence of irrelevant artifacts learned by DL-based detectors., Comment: Accepted by Tosem

Mobile malware has become one of the most critical security threats in the era of ubiquitous mobile computing. Despite the intensive efforts from security experts to counteract it, recent years have still witnessed a rapid growth of identified malware samples. This could be partly attributed to the newly-emerged technologies that may constantly open up under-studied attack surfaces for the adversaries. One typical example is the recently-developed mobile machine learning (ML) framework that enables storing and running deep learning (DL) models on mobile devices. Despite obvious advantages, this new feature also inadvertently introduces potential vulnerabilities (e.g., on-device models may be modified for malicious purposes). In this work, we propose a method to generate or transform mobile malware by hiding the malicious payloads inside the parameters of deep learning models, based on a strategy that considers four factors (layer type, layer number, layer coverage and the number of bytes to replace). Utilizing the proposed method, we can run malware in DL mobile applications covertly with little impact on the model performance (i.e., as little as 0.4% drop in accuracy and at most 39ms latency overhead)., Comment: Due to the limitation "The abstract field cannot be longer than 1,920 characters", the abstract here is shorter than that in the PDF file

Vision-language pre-trained (VLP) models have been the foundation of numerous vision-language tasks. Given their prevalence, it becomes imperative to assess their adversarial robustness, especially when deploying them in security-crucial real-world applications. Traditionally, adversarial perturbations generated for this assessment target specific VLP models, datasets, and/or downstream tasks. This practice suffers from low transferability and additional computation costs when transitioning to new scenarios. In this work, we thoroughly investigate whether VLP models are commonly sensitive to imperceptible perturbations of a specific pattern for the image modality. To this end, we propose a novel black-box method to generate Universal Adversarial Perturbations (UAPs), which is so called the Effective and T ransferable Universal Adversarial Attack (ETU), aiming to mislead a variety of existing VLP models in a range of downstream tasks. The ETU comprehensively takes into account the characteristics of UAPs and the intrinsic cross-modal interactions to generate effective UAPs. Under this regime, the ETU encourages both global and local utilities of UAPs. This benefits the overall utility while reducing interactions between UAP units, improving the transferability. To further enhance the effectiveness and transferability of UAPs, we also design a novel data augmentation method named ScMix. ScMix consists of self-mix and cross-mix data transformations, which can effectively increase the multi-modal data diversity while preserving the semantics of the original data. Through comprehensive experiments on various downstream tasks, VLP models, and datasets, we demonstrate that the proposed method is able to achieve effective and transferrable universal adversarial attacks., Comment: 9 pages, 5 figures

Corruptions due to data perturbations and label noise are prevalent in the datasets from unreliable sources, which poses significant threats to model training. Despite existing efforts in developing robust models, current learning methods commonly overlook the possible co-existence of both corruptions, limiting the effectiveness and practicability of the model. In this paper, we develop an Effective and Robust Adversarial Training (ERAT) framework to simultaneously handle two types of corruption (i.e., data and label) without prior knowledge of their specifics. We propose a hybrid adversarial training surrounding multiple potential adversarial perturbations, alongside a semi-supervised learning based on class-rebalancing sample selection to enhance the resilience of the model for dual corruption. On the one hand, in the proposed adversarial training, the perturbation generation module learns multiple surrogate malicious data perturbations by taking a DNN model as the victim, while the model is trained to maintain semantic consistency between the original data and the hybrid perturbed data. It is expected to enable the model to cope with unpredictable perturbations in real-world data corruption. On the other hand, a class-rebalancing data selection strategy is designed to fairly differentiate clean labels from noisy labels. Semi-supervised learning is performed accordingly by discarding noisy labels. Extensive experiments demonstrate the superiority of the proposed ERAT framework., Comment: 12 pages, 8 figures

We present PAODING, a toolkit to debloat pretrained neural network models through the lens of data-free pruning. To preserve the model fidelity, PAODING adopts an iterative process, which dynamically measures the effect of deleting a neuron to identify candidates that have the least impact to the output layer. Our evaluation shows that PAODING can significantly reduce the model size, generalize on different datasets and models, and meanwhile preserve the model fidelity in terms of test accuracy and adversarial robustness. PAODING is publicly available on PyPI via https://pypi.org/project/paoding-dl., Comment: 3 pages

The Thread protocol (or simply Thread ) is a popular networking protocol for the Internet of Things (IoT). It allows seamless integration of a set of applications and protocols, hence reducing the risk of incompatibility among different applications or user protocols. Thread has been deployed in many popular smart home products by the majority of IoT manufacturers, such as Apple TV, Apple HomePod mini, eero 6, Nest Hub, and Nest Wifi. Despite a few empirical analyses on the security of Thread, there is still a lack of formal analysis on this infrastructure of the booming IoT ecosystem. In this work, we performed a formal symbolic analysis of the security properties of Thread. Our main focus is on MeshCoP (Mesh Commissioning Protocol), the main subprotocol in Thread for secure authentication and commissioning of new, untrusted devices inside an existing Thread network. This case study presents the challenges and proposed solutions in modeling MeshCoP. We use ProVerif, a symbolic verification tool of {\pi}-calculus models, for verifying the security properties of MeshCoP., Comment: 18 pages

The collaborative nature of federated learning (FL) poses a major threat in the form of manipulation of local training data and local updates, known as the Byzantine poisoning attack. To address this issue, many Byzantine-robust aggregation rules (AGRs) have been proposed to filter out or moderate suspicious local updates uploaded by Byzantine participants. This paper introduces a novel approach called AGRAMPLIFIER, aiming to simultaneously improve the robustness, fidelity, and efficiency of the existing AGRs. The core idea of AGRAMPLIFIER is to amplify the "morality" of local updates by identifying the most repressive features of each gradient update, which provides a clearer distinction between malicious and benign updates, consequently improving the detection effect. To achieve this objective, two approaches, namely AGRMP and AGRXAI, are proposed. AGRMP organizes local updates into patches and extracts the largest value from each patch, while AGRXAI leverages explainable AI methods to extract the gradient of the most activated features. By equipping AGRAMPLIFIER with the existing Byzantine-robust mechanisms, we successfully enhance the model's robustness, maintaining its fidelity and improving overall efficiency. AGRAMPLIFIER is universally compatible with the existing Byzantine-robust mechanisms. The paper demonstrates its effectiveness by integrating it with all mainstream AGR mechanisms. Extensive evaluations conducted on seven datasets from diverse domains against seven representative poisoning attacks consistently show enhancements in robustness, fidelity, and efficiency, with average gains of 40.08%, 39.18%, and 10.68%, respectively., Comment: Accepted by IEEE TIFS, this is the complete version

When deploying pre-trained neural network models in real-world applications, model consumers often encounter resource-constraint platforms such as mobile and smart devices. They typically use the pruning technique to reduce the size and complexity of the model, generating a lighter one with less resource consumption. Nonetheless, most existing pruning methods are proposed with the premise that the model after being pruned has a chance to be fine-tuned or even retrained based on the original training data. This may be unrealistic in practice, as the data controllers are often reluctant to provide their model consumers with the original data. In this work, we study the neural network pruning in the data-free context, aiming to yield lightweight models that are not only accurate in prediction but also robust against undesired inputs in open-world deployments. Considering the absence of the fine-tuning and retraining that can fix the mis-pruned units, we replace the traditional aggressive one-shot strategy with a conservative one that treats the pruning as a progressive process. We propose a pruning method based on stochastic optimization that uses robustness-related metrics to guide the pruning process. Our method is implemented as a Python program and evaluated with a series of experiments on diverse neural network models. The experimental results show that it significantly outperforms existing one-shot data-free pruning approaches in terms of robustness preservation and accuracy.

Neural networks have been widely applied in security applications such as spam and phishing detection, intrusion prevention, and malware detection. This black-box method, however, often has uncertainty and poor explainability in applications. Furthermore, neural networks themselves are often vulnerable to adversarial attacks. For those reasons, there is a high demand for trustworthy and rigorous methods to verify the robustness of neural network models. Adversarial robustness, which concerns the reliability of a neural network when dealing with maliciously manipulated inputs, is one of the hottest topics in security and machine learning. In this work, we survey existing literature in adversarial robustness verification for neural networks and collect 39 diversified research works across machine learning, security, and software engineering domains. We systematically analyze their approaches, including how robustness is formulated, what verification techniques are used, and the strengths and limitations of each technique. We provide a taxonomy from a formal verification perspective for a comprehensive understanding of this topic. We classify the existing techniques based on property specification, problem reduction, and reasoning strategies. We also demonstrate representative techniques that have been applied in existing studies with a sample model. Finally, we discuss open questions for future research.

Federated learning enables multiple participants to collaboratively train a model without aggregating the training data. Although the training data are kept within each participant and the local gradients can be securely synthesized, recent studies have shown that such privacy protection is insufficient. The global model parameters that have to be shared for optimization are susceptible to leak information about training data. In this work, we propose Confined Gradient Descent (CGD) that enhances privacy of federated learning by eliminating the sharing of global model parameters. CGD exploits the fact that a gradient descent optimization can start with a set of discrete points and converges to another set at the neighborhood of the global minimum of the objective function. It lets the participants independently train on their local data, and securely share the sum of local gradients to benefit each other. We formally demonstrate CGD's privacy enhancement over traditional FL. We prove that less information is exposed in CGD compared to that of traditional FL. CGD also guarantees desired model accuracy. We theoretically establish a convergence rate for CGD. We prove that the loss of the proprietary models learned for each participant against a model learned by aggregated training data is bounded. Extensive experimental results on two real-world datasets demonstrate the performance of CGD is comparable with the centralized learning, with marginal differences on validation loss (mostly within 0.05) and accuracy (mostly within 1%).

Malware analysis is still largely a manual task. This slow and inefficient approach does not scale to the exponential rise in the rate of new unique malware generated. Hence, automating the process as much as possible becomes desirable. In this paper, we present ColdPress - an extensible malware analysis platform that automates the end-to-end process of malware threat intelligence gathering integrated output modules to perform report generation of arbitrary file formats. ColdPress combines state-of-the-art tools and concepts into a modular system that aids the analyst to efficiently and effectively extract information from malware samples. It is designed as a user-friendly and extensible platform that can be easily extended with user-defined modules. We evaluated ColdPress with complex real-world malware samples (e.g., WannaCry), demonstrating its efficiency, performance and usefulness to security analysts., Comment: The code is open source at https://github.com/uqcyber/ColdPress

Industrial control systems (ICS) of critical infrastructure are increasingly connected to the Internet for remote site management at scale. However, cyber attacks against ICS - especially at the communication channels between humanmachine interface (HMIs) and programmable logic controllers (PLCs) - are increasing at a rate which outstrips the rate of mitigation. In this paper, we introduce a vendor-agnostic analytics framework which allows security researchers to analyse attacks against ICS systems, even if the researchers have zero control automation domain knowledge or are faced with a myriad of heterogenous ICS systems. Unlike existing works that require expertise in domain knowledge and specialised tool usage, our analytics framework does not require prior knowledge about ICS communication protocols, PLCs, and expertise of any network penetration testing tool. Using `digital twin' scenarios comprising industry-representative HMIs, PLCs and firewalls in our test lab, our framework's steps were demonstrated to successfully implement a stealthy deception attack based on false data injection attacks (FDIA). Furthermore, our framework also demonstrated the relative ease of attack dataset collection, and the ability to leverage well-known penetration testing tools. We also introduce the concept of `heuristic inference attacks', a new family of attack types on ICS which is agnostic to PLC and HMI brands/models commonly deployed in ICS. Our experiments were also validated on a separate ICS dataset collected from a cyber-physical scenario of water utilities. Finally, we utilized time complexity theory to estimate the difficulty for the attacker to conduct the proposed packet analyses, and recommended countermeasures based on our findings.

Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Info & Comm Tech, Science, Environment, Engineering and Technology, We live in an increasingly interconnected, complex world, where our collective decisions can have unanticipated indirect consequences on the world. What is today a hands-on job may soon be a job of managing variables at a computer screen. However, people have tremendous difficulty handling even relatively mild levels of complexity in experiments. Yet, in the context of many modern computer games, people eagerly teach themselves vastly complex systems, all without any external guidance or coercion. Educational video games research is a menagerie of different methodologies and paradigms. Meta analyses have found that mixed results in the literature are difficult to interpret due to the combination of different theoretical approaches, different data reporting conventions, and a general focus on proof-of-concept studies. They recommend a transition to narrower investigations of specific causal relationships between game properties and outcomes of engagement and learning, but this requires a way to incorporate them into the broader picture of educational and serious games research. In this thesis, I focus on educational games and propose the Model-Master-Transfer (MMT) framework to break down educational game usage into a set of formal subprocesses that can be studied in more depth individually, and specify how such narrow studies can then be assembled to build up a causal model of the underlying effects. The framework is illustrated using different educational examples. The conceptual study contributes a comprehensive framework to the ambiguous research on educational learning using games. MMT is then used in empirical experiments to address two sub-problems: 1) Why players sometimes choose to lose the game, completely derailing its intended purpose; 2) The design of inherently learnable systems in terms of how the complexity of a game relates to the player’s ability to master it - searching for forms of complexity that elicit curiosity to learn about that complexity. T

Educational games research is a menagerie of different methodologies and paradigms. Mixed results in the literature are difficult to interpret due to the combination of different theoretical frames, different data reporting conventions, and a genera! focus on proof-of-concept studies. Narrower investigations of specific causal relationships between game properties and outcomes of engagement and learning can provide more specific findings, but require a way to incorporate them into the broader picture of educational games research. In this study, we focus on educational games and propose the Model-Master-Transfer (MMT) framework to break down educa-tional game usage into a set of formal sub-processcs that can be studied in more depth individually, and specify how such narrow studies can then be assembled to build up a causal model of the underlying effects. The framework is illustrated using different educational examples. The conceptual study contributes a comprehensive framework to the ambiguous re-search on educational learning using games. Additionally, it provides practical implications for game developers and educators alike.

We live in an increasingly interconnected, complex world, where our collective decisions can have unanticipated indirect consequences on the world. What is today a hands-on job may soon be a job of managing variables at a computer screen. However, people have tremendous difficulty handling even relatively mild levels of complexity in experiments. Yet, in the context of many modern computer games, people eagerly teach themselves vastly complex systems, all without any external guidance or coercion. Educational video games research is a menagerie of different methodologies and paradigms. Meta analyses have found that mixed results in the literature are difficult to interpret due to the combination of different theoretical approaches, different data reporting conventions, and a general focus on proof-of-concept studies. They recommend a transition to narrower investigations of specific causal relationships between game properties and outcomes of engagement and learning, but this requires a way to incorporate them into the broader picture of educational and serious games research. In this thesis, I focus on educational games and propose the Model-Master-Transfer (MMT) framework to break down educational game usage into a set of formal subprocesses that can be studied in more depth individually, and specify how such narrow studies can then be assembled to build up a causal model of the underlying effects. The framework is illustrated using different educational examples. The conceptual study contributes a comprehensive framework to the ambiguous research on educational learning using games. MMT is then used in empirical experiments to address two sub-problems: 1) Why players sometimes choose to lose the game, completely derailing its intended purpose; 2) The design of inherently learnable systems in terms of how the complexity of a game relates to the player’s ability to master it - searching for forms of complexity that elicit curiosity to learn about that complexity. T, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Info & Comm Tech, Science, Environment, Engineering and Technology, Full Text

As COVID-19 has been spreading across the world since early 2020, a growing number of malicious campaigns are capitalizing the topic of COVID-19. COVID-19 themed cryptocurrency scams are increasingly popular during the pandemic. However, these newly emerging scams are poorly understood by our community. In this paper, we present the first measurement study of COVID-19 themed cryptocurrency scams. We first create a comprehensive taxonomy of COVID-19 scams by manually analyzing the existing scams reported by users from online resources. Then, we propose a hybrid approach to perform the investigation by: 1) collecting reported scams in the wild; and 2) detecting undisclosed ones based on information collected from suspicious entities (e.g., domains, tweets, etc). We have collected 195 confirmed COVID-19 cryptocurrency scams in total, including 91 token scams, 19 giveaway scams, 9 blackmail scams, 14 crypto malware scams, 9 Ponzi scheme scams, and 53 donation scams. We then identified over 200 blockchain addresses associated with these scams, which lead to at least 330K US dollars in losses from 6,329 victims. For each type of scams, we further investigated the tricks and social engineering techniques they used. To facilitate future research, we have released all the well-labelled scams to the research community.

Collaborative learning enables two or more participants, each with their own training dataset, to collaboratively learn a joint model. It is desirable that the collaboration should not cause the disclosure of either the raw datasets of each individual owner or the local model parameters trained on them. This privacy-preservation requirement has been approached through differential privacy mechanisms, homomorphic encryption (HE) and secure multiparty computation (MPC), but existing attempts may either introduce the loss of model accuracy or imply significant computational and/or communicational overhead. In this work, we address this problem with the lightweight additive secret sharing technique. We propose PrivColl, a framework for protecting local data and local models while ensuring the correctness of training processes. PrivColl employs secret sharing technique for securely evaluating addition operations in a multiparty computation environment, and achieves practicability by employing only the homomorphic addition operations. We formally prove that it guarantees privacy preservation even though the majority (n-2 out of n) of participants are corrupted. With experiments on real-world datasets, we further demonstrate that PrivColl retains high efficiency. It achieves a speedup of more than 45X over the state-of-the-art MPC/HE based schemes for training linear/logistic regression, and 216X faster for training neural network., Comment: 20 pages, 3 figures, to be published in 25th European Symposium on Research in Computer Security (ESORICS) 2020

Cryptocurrency has seen an explosive growth in recent years, thanks to the evolvement of blockchain technology and its economic ecosystem. Besides Bitcoin, thousands of cryptocurrencies have been distributed on blockchains, while hundreds of cryptocurrency exchanges are emerging to facilitate the trading of digital assets. At the same time, it also attracts the attentions of attackers. Fake deposit, as one of the most representative attacks (vulnerabilities) related to exchanges and tokens, has been frequently observed in the blockchain ecosystem, causing large financial losses. However, besides a few security reports, our community lacks of the understanding of this vulnerability, for example its scale and the impacts. In this paper, we take the first step to demystify the fake deposit vulnerability. Based on the essential patterns we have summarized, we implement DEPOSafe, an automated tool to detect and verify (exploit) the fake deposit vulnerability in ERC-20 smart contracts. DEPOSafe incorporates several key techniques including symbolic execution based static analysis and behavior modeling based dynamic verification. By applying DEPOSafe to 176,000 ERC-20 smart contracts, we have identified over 7,000 vulnerable contracts that may suffer from two types of attacks. Our findings demonstrate the urgency to identify and prevent the fake deposit vulnerability., Comment: 10 pages, 6 figures

Ever since the beginning of the outbreak of the COVID-19 pandemic, researchers from interdisciplinary domains have worked together to fight against the crisis. The open source community, plays a vital role in coping with the pandemic which is inherently a collaborative process. Plenty of COVID-19 related datasets, tools, software, deep learning models, are created and shared in research communities with great efforts. However, COVID-19 themed open source projects have not been systematically studied, and we are still unaware how the open source community helps combat COVID-19 in practice. To fill this void, in this paper, we take the first step to study COVID-19 themed repositories in GitHub, one of the most popular collaborative platforms. We have collected over 67K COVID-19 themed GitHub repositories till July 2020. We then characterize them from a number of aspects and classify them into six categories. We further investigate the contribution patterns of the contributors, and development and maintenance patterns of the repositories. This study sheds light on the promising direction of adopting open source technologies and resources to rapidly tackle the worldwide public health emergency in practice, and reveals existing challenges for improvement.

The number of Android smartphone and tablet users has experienced a rapid growth in the past few years and it raises users' awareness on the privacy and security of their mobile devices. The features of openness and extensibility make Android unique, attractive and competitive but meanwhile vulnerable to malicious attack. There are lots of users rooting their Android devices for some useful functions, which are not originally provided to developers and users, such as backup and taking screenshot. However, after observing the danger of rooting devices, the developers begin to look for other non-root alternatives to implement those functions. ADB workaround is one of the best known non-root alternatives to help app gain higher privilege on Android. It used to be considered as a secure practice until some cases of ADB privilege leakage have been found. In this project, we design an approach and implement a couple of tools to detect the privilege leakage in Android apps. We apply them to analyse three real-world apps with millions of users, and successfully identify three ADB privilege leaks from them. Moreover, we also conduct an exploitation of the ADB privilege in one app, and therefore we prove the existence of vulnerabilities in ADB workaround. Based on out study, we propose some suggestion to help developers create their apps that could not only satisfy users' needs but also protect users' privacy from similar attacks in future., Comment: 13 pages

Social media platforms contain a great wealth of information which provides opportunities for us to explore hidden patterns or unknown correlations, and understand people's satisfaction with what they are discussing. As one showcase, in this paper, we present a system, TwiInsight which explores the insight of Twitter data. Different from other Twitter analysis systems, TwiInsight automatically extracts the popular topics under different categories (e.g., healthcare, food, technology, sports and transport) discussed in Twitter via topic modeling and also identifies the correlated topics across different categories. Additionally, it also discovers the people's opinions on the tweets and topics via the sentiment analysis. The system also employs an intuitive and informative visualization to show the uncovered insight. Furthermore, we also develop and compare six most popular algorithms - three for sentiment analysis and three for topic modeling.