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David Arroyo

Publications and source records attributed to David Arroyo.

At least 19 recordsLinked to original sources
arXiv2025

Analysing Multidisciplinary Approaches to Fight Large-Scale Digital Influence Operations

Crime as a Service (CaaS) has evolved from isolated criminal incidents to a broad spectrum of illicit activities, including social media manipulation, foreign information manipulation and interference (FIMI), and the sale of disinformation toolkits. This article analyses how threat actors exploit specialised infrastructures ranging from proxy and VPN services to AI-driven generative models to orchestrate large-scale opinion manipulation. Moreover, it discusses how these malicious operations monetise the virality of social networks, weaponise dual-use technologies, and leverage user biases to amplify polarising narratives. In parallel, it examines key strategies for detecting, attributing, and mitigating such campaigns by highlighting the roles of blockchain-based content verification, advanced cryptographic proofs, and cross-disciplinary collaboration. Finally, the article highlights that countering disinformation demands an integrated framework that combines legal, technological, and societal efforts to address a rapidly adapting and borderless threat

cs.CY↗
arXiv2024

The Malware as a Service ecosystem

The goal of this chapter is to illuminate the operational frameworks, key actors, and significant cybersecurity implications of the Malware as a Service (MaaS) ecosystem. Highlighting the transformation of malware proliferation into a service-oriented model, the chapter discusses how MaaS democratises access to sophisticated cyberattack capabilities, enabling even those with minimal technical knowledge to execute catastrophic cyberattacks. The discussion extends to the roles within the MaaS ecosystem, including malware developers, affiliates, initial access brokers, and the essential infrastructure providers that support these nefarious activities. The study emphasises the profound challenges MaaS poses to traditional cybersecurity defences, rendered ineffective against the constantly evolving and highly adaptable threats generated by MaaS platforms. With the increase in malware sophistication, there is a parallel call for a paradigm shift in defensive strategies, advocating for dynamic analysis, behavioural detection, and the integration of AI and machine learning techniques. By exploring the intricacies of the MaaS ecosystem, including the economic motivations driving its growth and the blurred lines between legitimate service models and cyber crime, the chapter presents a comprehensive overview intended to foster a deeper understanding among researchers and cybersecurity professionals. The ultimate goal is to aid in developing more effective strategies for combating the spread of commoditised malware threats and safeguarding against the increasing accessibility and scalability of cyberattacks facilitated by the MaaS model.

cs.CR↗
arXiv2024

Investigating child sexual abuse material availability, searches, and users on the anonymous Tor network for a public health intervention strategy

Tor is widely used for staying anonymous online and accessing onion websites; unfortunately, Tor is popular for distributing and viewing illicit child sexual abuse material (CSAM). From 2018 to 2023, we analyse 176,683 onion domains and find that one-fifth share CSAM. We find that CSAM is easily available using 21 out of the 26 most-used Tor search engines. We analyse 110,133,715 search sessions from the Ahmia.fi search engine and discover that 11.1% seek CSAM. When searching CSAM by age, 40.5% search for 11-year-olds and younger; 11.0% for 12-year-olds; 8.2% for 13-year-olds; 11.6% for 14-year-olds; 10.9% for 15-year-olds; and 12.7% for 16-year-olds. We demonstrate accurate filtering for search engines, introduce intervention, show a questionnaire for CSAM users, and analyse 11,470 responses. 65.3% of CSAM users first saw the material when they were children themselves, and half of the respondents first saw the material accidentally, demonstrating the availability of CSAM. 48.1% want to stop using CSAM. Some seek help through Tor, and self-help websites are popular. Our survey finds commonalities between CSAM use and addiction. Help-seeking correlates with increasing viewing duration and frequency, depression, anxiety, self-harming thoughts, guilt, and shame. Yet, 73.9% of help seekers have not been able to receive it.

cs.CR↗
arXiv2024

A Cybersecurity Risk Analysis Framework for Systems with Artificial Intelligence Components

The introduction of the European Union Artificial Intelligence Act, the NIST Artificial Intelligence Risk Management Framework, and related norms demands a better understanding and implementation of novel risk analysis approaches to evaluate systems with Artificial Intelligence components. This paper provides a cybersecurity risk analysis framework that can help assessing such systems. We use an illustrative example concerning automated driving systems.

cs.AI↗
arXiv2019

A compression based framework for the detection of anomalies in heterogeneous data sources

Nowadays, information and communications technology systems are fundamental assets of our social and economical model, and thus they should be properly protected against the malicious activity of cybercriminals. Defence mechanisms are generally articulated around tools that trace and store information in several ways, the simplest one being the generation of plain text files coined as security logs. This log files are usually inspected, in a semi-automatic way, by security analysts to detect events that may affect system integrity. On this basis, we propose a parameter-free methodology to detect security incidents from structured text regardless its nature. We use the Normalized Compression Distance to obtain a set of features that can be used by a Support Vector Machine to classify events from a heterogeneous cybersecurity environment. In specific, we explore and validate the application of our methodology in four different cybersecurity domains: HTTP anomaly identification, spam detection, Domain Generation Algorithms tracking and sentiment analysis. The results obtained show the validity and flexibility of our approach in different security scenarios with a low configuration burden.

cs.CR↗
arXiv2016

Combining Usability and Privacy Protection in Free-Access Public Cloud Storage Servers: Review of the Main Threats and Challenges

The 21st century belongs to the world of computing, specially as a result of the so-called cloud computing. This technology enables ubiquitous information management and thus people can access all their data from any place and at any time. In this landscape, the emergence of cloud storage has had an important role in the last five years. Nowadays, several free-access public cloud storage services make it possible for users to have a free backup of their assets and to manage and share them, representing a low-cost opportunity for Small and Medium Companies (SME). However, the adoption of cloud storage involves data outsourcing, so a user does not have the guarantee about the way her data will be processed and protected. Therefore, it seems necessary to endow public cloud storage with a set of means to protect users' confidentiality and privacy, to assess data integrity and to guarantee a proper backup of information assets. Along this paper we discuss the main challenges to achieve such a goal, underlining the set of functionalities already implemented in the most popular public cloud storage services.

cs.CR↗
arXiv2016

Cryptanalysis of a Classical chaos-based cryptosystem with some quantum cryptography features

The application of synchronization theory to build up new cryptosystems has been a hot topic during the last two decades. In this paper we analyze a recent proposal in this field. We pinpoint the main limitations of the software implementation of chaos-based systems designed on the grounds of synchronization theory. In addition, we show that the cryptosystem under evaluation possesses serious security problems that imply a clear reduction of the key space.

cs.CR↗
arXiv2014

Fair anonymity for the Tor network

Current anonymizing networks have become an important tool for guaranteeing users' privacy. However, these platforms can be used to perform illegitimate actions, which sometimes makes service providers see traffic coming from these networks as a probable threat. In order to solve this problem, we propose to add support for fairness mechanisms to the Tor network. Specifically, by introducing a slight modification to the key negotiation process with the entry and exit nodes, in the shape of group signatures. By means of these signatures, we set up an access control method to prevent misbehaving users to make use of the Tor network. Additionally, we establish a predefined method for denouncing illegitimate actions, which impedes the application of the proposed fairness mechanisms as a threat eroding users' privacy. As a direct consequence, traffic coming from Tor would be considered less suspicious by service providers.

cs.CR↗
arXiv2012

Formal security analysis of registration protocols for interactive systems: a methodology and a case of study

In this work we present and formally analyze CHAT-SRP (CHAos based Tickets-Secure Registration Protocol), a protocol to provide interactive and collaborative platforms with a cryptographically robust solution to classical security issues. Namely, we focus on the secrecy and authenticity properties while keeping a high usability. In this sense, users are forced to blindly trust the system administrators and developers. Moreover, as far as we know, the use of formal methodologies for the verification of security properties of communication protocols isn't yet a common practice. We propose here a methodology to fill this gap, i.e., to analyse both the security of the proposed protocol and the pertinence of the underlying premises. In this concern, we propose the definition and formal evaluation of a protocol for the distribution of digital identities. Once distributed, these identities can be used to verify integrity and source of information. We base our security analysis on tools for automatic verification of security protocols widely accepted by the scientific community, and on the principles they are based upon. In addition, it is assumed perfect cryptographic primitives in order to focus the analysis on the exchange of protocol messages. The main property of our protocol is the incorporation of tickets, created using digests of chaos based nonces (numbers used only once) and users' personal data. Combined with a multichannel authentication scheme with some previous knowledge, these tickets provide security during the whole protocol by univocally linking each registering user with a single request. [..]

cs.CR↗
arXiv2012

A formal methodology for integral security design and verification of network protocols

We propose a methodology for verifying security properties of network protocols at design level. It can be separated in two main parts: context and requirements analysis and informal verification; and formal representation and procedural verification. It is an iterative process where the early steps are simpler than the last ones. Therefore, the effort required for detecting flaws is proportional to the complexity of the associated attack. Thus, we avoid wasting valuable resources for simple flaws that can be detected early in the verification process. In order to illustrate the advantages provided by our methodology, we also analyze three real protocols.

cs.CR↗
arXiv2012

Application of Gray codes to the study of the theory of symbolic dynamics of unimodal maps

In this paper we provide a closed mathematical formulation of our previous results in the field of symbolic dynamics of unimodal maps. This being the case, we discuss the classical theory of applied symbolic dynamics for unimodal maps and its reinterpretation using Gray codes. This connection was previously emphasized but no explicit mathematical proof was provided. The work described in this paper not only contributes to the integration of the different interpretations of symbolic dynamics of unimodal maps, it also points out some inaccuracies that exist in previous works.

nlin.CD↗
arXiv2012

Cryptanalysis of a one round chaos-based Substitution Permutation Network

The interleaving of chaos and cryptography has been the aim of a large set of works since the beginning of the nineties. Many encryption proposals have been introduced to improve conventional cryptography. However, many proposals possess serious problems according to the basic requirements for the secure exchange of information. In this paper we highlight some of the main problems of chaotic cryptography by means of the analysis of a very recent chaotic cryptosystem based on a one round Substitution Permutation Network. More specifically, we show that it is not possible to avoid the security problems of that encryption architecture just by including a chaotic system as core of the derived encryption system.

nlin.CD↗
arXiv2009

Breaking a Chaotic Cryptographic Scheme Based on Composition Maps

Recently, a chaotic cryptographic scheme based on composition maps was proposed. This paper studies the security of the scheme and reports the following findings: 1) the scheme can be broken by a differential attack with $6+\lceil\log_L(MN)\rceil$ chosen-plaintext, where $MN$ is the size of plaintext and $L$ is the number of different elements in plain-text; 2) the scheme is not sensitive to the changes of plaintext; 3) the two composition maps do not work well as a secure and efficient random number source.

cs.CR↗
arXiv2009

Cryptanalysis of a family of self-synchronizing chaotic stream ciphers

Unimodal maps have been broadly used as a base of new encryption strategies. Recently, a stream cipher has been proposed in the literature, whose keystream is basically a symbolic sequence of the (one-parameter) logistic map or of the tent map. In the present work a thorough analysis of the keystream is made which reveals the existence of some serious security problems

nlin.CD↗
arXiv2008

Estimation of the control parameter from symbolic sequences: Unimodal maps with variable critical point

The work described in this paper can be interpreted as an application of the order patterns of symbolic dynamics when dealing with unimodal maps. Specifically, it is shown how Gray codes can be used to estimate the probability distribution functions (PDFs) of the order patterns of parametric unimodal maps. Furthermore, these PDFs depend on the value of the parameter, what eventually provides a handle to estimate the parameter value from symbolic sequences (in form of Gray codes), even when the critical point depends on the parameter.

nlin.CD↗
arXiv2008

A Basic Framework for the Cryptanalysis of Digital Chaos-Based Cryptography

Chaotic cryptography is based on the properties of chaos as source of entropy. Many different schemes have been proposed to take advantage of those properties and to design new strategies to encrypt information. However, the right and efficient use of chaos in the context of cryptography requires a thorough knowledge about the dynamics of the selected chaotic system. Indeed, if the final encryption system reveals enough information about the underlying chaotic system it could be possible for a cryptanalyst to get the key, part of the key or some information somehow equivalent to the key just analyzing those dynamical properties leaked by the cryptosystem. This paper shows what those dynamical properties are and how a cryptanalyst can use them to prove the inadequacy of an encryption system for the secure exchange of information. This study is performed through the introduction of a series of mathematical tools which should be the basic framework of cryptanalysis in the context of digital chaos-based cryptography.

cs.CR↗