Adversarial Machine Learning: Bayesian Perspectives

Adversarial Machine Learning (AML) is emerging as a major field aimed at protecting machine learning (ML) systems against security threats: in certain scenarios there may be adversaries that actively manipulate input data to fool learning systems. This creates a new class of security vulnerabilities that ML systems may face, and a new desirable property called adversarial robustness essential to trust operations based on ML outputs. Most work in AML is built upon a game-theoretic modelling of the conflict between a learning system and an adversary, ready to manipulate input data. This assumes that each agent knows their opponent's interests and uncertainty judgments, facilitating inferences based on Nash equilibria. However, such common knowledge assumption is not realistic in the security scenarios typical of AML. After reviewing such game-theoretic approaches, we discuss the benefits that Bayesian perspectives provide when defending ML-based systems. We demonstrate how the Bayesian approach allows us to explicitly model our uncertainty about the opponent's beliefs and interests, relaxing unrealistic assumptions, and providing more robust inferences. We illustrate this approach in supervised learning settings, and identify relevant future research problems

Command & Control: Understanding, Denying and Detecting - A review of malware C2 techniques, detection and defences

In this survey, we first briefly review the current state of cyber attacks, highlighting significant recent changes in how and why such attacks are performed. We then investigate the mechanics of malware command and control (C2) establishment: we provide a comprehensive review of the techniques used by attackers to set up such a channel and to hide its presence from the attacked parties and the security tools they use. We then switch to the defensive side of the problem, and review approaches that have been proposed for the detection and disruption of C2 channels. We also map such techniques to widely-adopted security controls, emphasizing gaps or limitations (and success stories) in current best practices.Comment: Work commissioned by CPNI, available at c2report.org. 38 pages. Listing abstract compressed from version appearing in repor

Contribuciones a la Seguridad del Aprendizaje Automático

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Matemáticas, leída el 05-11-2020Machine learning (ML) applications have experienced an unprecedented growth over the last two decades. However, the ever increasing adoption of ML methodologies has revealed important security issues. Among these, vulnerabilities to adversarial examples, data instances targeted at fooling ML algorithms, are especially important. Examples abound. For instance, it is relatively easy to fool a spam detector simply misspelling spam words. Obfuscation of malware code can make it seem legitimate. Simply adding stickers to a stop sign could make an autonomous vehicle classify it as a merge sign. Consequences could be catastrophic. Indeed, ML is designed to work in stationary and benign environments. However, in certain scenarios, the presence of adversaries that actively manipulate input datato fool ML systems to attain benefits break such stationarity requirements. Training and operation conditions are not identical anymore. This creates a whole new class of security vulnerabilities that ML systems may face and a new desirable property: adversarial robustness. If we are to trust operations based on ML outputs, it becomes essential that learning systems are robust to such adversarial manipulations...Las aplicaciones del aprendizaje automático o machine learning (ML) han experimentado un crecimiento sin precedentes en las últimas dos décadas. Sin embargo, la adopción cada vez mayor de metodologías de ML ha revelado importantes problemas de seguridad. Entre estos, destacan las vulnerabilidades a ejemplos adversarios, es decir; instancias de datos destinadas a engañar a los algoritmos de ML. Los ejemplos abundan: es relativamente fácil engañar a un detector de spam simplemente escribiendo mal algunas palabras características de los correos basura. La ofuscación de código malicioso (malware) puede hacer que parezca legítimo. Agregando unos parches a una señal de stop, se podría provocar que un vehículo autónomo la reconociese como una señal de dirección obligatoria. Cómo puede imaginar el lector, las consecuencias de estas vulnerabilidades pueden llegar a ser catastróficas. Y es que el machine learning está diseñado para trabajar en entornos estacionarios y benignos. Sin embargo, en ciertos escenarios, la presencia de adversarios que manipulan activamente los datos de entrada para engañar a los sistemas de ML(logrando así beneficios), rompen tales requisitos de estacionariedad. Las condiciones de entrenamiento y operación de los algoritmos ya no son idénticas, quebrándose una de las hipótesis fundamentales del ML. Esto crea una clase completamente nueva de vulnerabilidades que los sistemas basados en el aprendizaje automático deben enfrentar y una nueva propiedad deseable: la robustez adversaria. Si debemos confiaren las operaciones basadas en resultados del ML, es esencial que los sistemas de aprendizaje sean robustos a tales manipulaciones adversarias...Fac. de Ciencias MatemáticasTRUEunpu

Distribution-Based Categorization of Classifier Transfer Learning

Transfer Learning (TL) aims to transfer knowledge acquired in one problem, the source problem, onto another problem, the target problem, dispensing with the bottom-up construction of the target model. Due to its relevance, TL has gained significant interest in the Machine Learning community since it paves the way to devise intelligent learning models that can easily be tailored to many different applications. As it is natural in a fast evolving area, a wide variety of TL methods, settings and nomenclature have been proposed so far. However, a wide range of works have been reporting different names for the same concepts. This concept and terminology mixture contribute however to obscure the TL field, hindering its proper consideration. In this paper we present a review of the literature on the majority of classification TL methods, and also a distribution-based categorization of TL with a common nomenclature suitable to classification problems. Under this perspective three main TL categories are presented, discussed and illustrated with examples

Transfer Learning using Computational Intelligence: A Survey

Abstract Transfer learning aims to provide a framework to utilize previously-acquired knowledge to solve new but similar problems much more quickly and effectively. In contrast to classical machine learning methods, transfer learning methods exploit the knowledge accumulated from data in auxiliary domains to facilitate predictive modeling consisting of different data patterns in the current domain. To improve the performance of existing transfer learning methods and handle the knowledge transfer process in real-world systems, ..

Graph based Anomaly Detection and Description: A Survey

Detecting anomalies in data is a vital task, with numerous high-impact applications in areas such as security, finance, health care, and law enforcement. While numerous techniques have been developed in past years for spotting outliers and anomalies in unstructured collections of multi-dimensional points, with graph data becoming ubiquitous, techniques for structured graph data have been of focus recently. As objects in graphs have long-range correlations, a suite of novel technology has been developed for anomaly detection in graph data. This survey aims to provide a general, comprehensive, and structured overview of the state-of-the-art methods for anomaly detection in data represented as graphs. As a key contribution, we give a general framework for the algorithms categorized under various settings: unsupervised vs. (semi-)supervised approaches, for static vs. dynamic graphs, for attributed vs. plain graphs. We highlight the effectiveness, scalability, generality, and robustness aspects of the methods. What is more, we stress the importance of anomaly attribution and highlight the major techniques that facilitate digging out the root cause, or the ‘why’, of the detected anomalies for further analysis and sense-making. Finally, we present several real-world applications of graph-based anomaly detection in diverse domains, including financial, auction, computer traffic, and social networks. We conclude our survey with a discussion on open theoretical and practical challenges in the field

Artist Ranking Through Analysis of On-line Community Comments

We describe an approach to measure the popularity of music tracks, albums and artists by analyzing the comments of music listeners in social networking online communities such as MySpace. This measure of popularity appears to be more accurate than the traditional measure based on album sales figures, as demonstrated by our focus group study. We faced many challenges in our attempt to generate a popularity ranking from the user comments on social networking sites, e.g., broken English sentences, comment spam, etc. We discuss the steps we took to overcome these challenges and describe an end to end system for generating a new popularity measure based on online comments, and the experiments performed to evaluate its success

Why is Machine Learning Security so hard?

The increase of available data and computing power has fueled a wide application of machine learning (ML). At the same time, security concerns are raised: ML models were shown to be easily fooled by slight perturbations on their inputs. Furthermore, by querying a model and analyzing output and input pairs, an attacker can infer the training data or replicate the model, thereby harming the owner’s intellectual property. Also, altering the training data can lure the model into producing specific or generally wrong outputs at test time. So far, none of the attacks studied in the field has been satisfactorily defended. In this work, we shed light on these difficulties. We first consider classifier evasion or adversarial examples. The computation of such examples is an inherent problem, as opposed to a bug that can be fixed. We also show that adversarial examples often transfer from one model to another, different model. Afterwards, we point out that the detection of backdoors (a training-time attack) is hindered as natural backdoor-like patterns occur even in benign neural networks. The question whether a pattern is benign or malicious then turns into a question of intention, which is hard to tackle. A different kind of complexity is added with the large libraries nowadays in use to implement machine learning. We introduce an attack that alters the library, thereby decreasing the accuracy a user can achieve. In case the user is aware of the attack, however, it is straightforward to defeat. This is not the case for most classical attacks described above. Additional difficulty is added if several attacks are studied at once: we show that even if the model is configured for one attack to be less effective, another attack might perform even better. We conclude by pointing out the necessity of understanding the ML model under attack. On the one hand, as we have seen throughout the examples given here, understanding precedes defenses and attacks. On the other hand, an attack, even a failed one, often yields new insights and knowledge about the algorithm studied.This work was supported by the German Federal Ministry of Education and Research (BMBF) through funding for the Center for IT-Security,Privacy and Accountability (CISPA) (FKZ: 16KIS0753