Machine Learning is the study of methods for programming computers to learn. Computers are applied to a wide range of tasks, and for most of these it is relatively easy for programmers to design and implement the necessary software. However, there are many tasks for which this is difficult or impossible. These can be divided into four general categories. First, there are problems for which there exist no human experts. For example, in modern automated manufacturing facilities, there is a need to predict machine failures before they occur by analyzing sensor readings. Because the machines are new, there are no human experts who can be interviewed by a programmer to provide the knowledge necessary to build a computer system. A machine learning system can study recorded data and subsequent machine failures and learn prediction rules. Second, there are problems where human experts exist, but where they are unable to explain their expertise. This is the case in many perceptual tasks, such as speech recognition, hand-writing recognition, and natural language understanding. Virtually all humans exhibit expert-level abilities on these tasks, but none of them can describe the detailed steps that they follow as they perform them. Fortunately, humans can provide machines with examples of the inputs and correct outputs for these tasks, so machine learning algorithms can learn to map the inputs to the outputs. Third, there are problems where phenomena are changing rapidly. In finance, for example, people would like to predict the future behavior of the stock market, of consumer purchases, or of exchange rates. These behaviors change frequently, so that even if a programmer could construct a good predictive computer program, it would need to be rewritten frequently. A learning program can relieve the programmer of this burden by constantly modifying and tuning a set of learned prediction rules. Fourth, there are applications that need to be customized for each computer user separately. Consider, for example, a program to filter unwanted electronic mail messages. Different users will need different filters. It is unreasonable to expect each user to program his or her own rules, and it is infeasible to provide every user with a software engineer to keep the rules up-to-date. A machine learning system can learn which mail messages the user rejects and maintain the filtering rules automatically. Machine learning addresses many of the same research questions as the fields of statistics, data mining, and psychology, but with differences of emphasis. Statistics focuses on understanding the phenomena that have generated the data, often with the goal of testing different hypotheses about those phenomena. Data mining seeks to find patterns in the data that are understandable by people. Psychological studies of human learning aspire to understand the mechanisms underlying the various learning behaviors exhibited by people (concept learning, skill acquisition, strategy change, etc.).

Machine learning

Data Mining Practical Machine Learning Tools and Techniques

Rapid growth in the volume of unsolicited and unwanted messages has inspired the development of many anti-spam methods. Supervised anti-spam filters using machine-learning methods have been particularly effective in categorizing spam and non-spam messages. These automatically integrate spam corpora pre-processing, appropriate word lists selection, and the calculation of word weights, usually in a bag-of-words fashion. To develop an accurate spam filter is challenging because spammers attempt to decrease the probability of spam detection by using legitimate words. Complex models are therefore needed to solve such a problem. However, existing spam filtering methods usually converge to a poor local minimum, cannot effectively handle high-dimensional data and suffer from overfitting issues. To overcome these problems, we propose a novel spam filter integrating an N-gram tf.idf feature selection, modified distribution-based balancing algorithm and a regularized deep multi-layer perceptron NN model with rectified linear units (DBB-RDNN-ReL). As demonstrated on four benchmark spam datasets (Enron, SpamAssassin, SMS spam collection and Social networking), the proposed approach enables capturing more complex features from high-dimensional data by additional layers of neurons. Another advantage of this approach is that no additional dimensionality reduction is necessary and spam dataset imbalance is addressed using a modified distribution-based algorithm. We compare the performance of the approach with that of state-of-the-art spam filters (Minimum Description Length, Factorial Design using SVM and NB, Incremental Learning C4.5, and Random Forest, Voting and Convolutional Neural Network) and several machine learning algorithms commonly used to classify text. We show that the proposed model outperforms these other methods in terms of classification accuracy, with fewer false negatives and false positives. Notably, the proposed spam filter classifies both major (legitimate) and minor (spam) classes well on personalized / non-personalized and balanced / imbalanced spam datasets. In addition, we show that the proposed model performs better than the results reported by previous studies in terms of accuracy. However, the high computational expenses related to additional hidden layers limit its application as an online spam filter and make it difficult to overcome the problem of concept drift.

/pdf/spam-filtering-using-integrated-distribution-based-balancing-2b91ho97sj.pdf

Spam filtering using integrated distribution-based balancing approach and regularized deep neural networks

Towards automatic filtering of fake reviews

In the last years, the popularity of smartphones and social networks has been contributing to the spread of fake news. Through these electronic media, this type of news can deceive thousands of people in a short time and cause great harm to individuals, companies, or society. Fake news has the potential to change a political scenario, to contribute to the spread of diseases, and even to cause deaths. Despite the efforts of several studies on fake news detection, most of them only cover English language news. There is a lack of labeled datasets of fake news in other languages and, moreover, important questions still remain open. For example, there is no consensus on what are the best classification strategies and sets of features to be used for automatic fake news detection. To answer this and other important open questions, we present a new public and real dataset of labeled true and fake news in Portuguese, and we perform a comprehensive analysis of machine learning methods for fake news detection. The experiments were performed using different sets of features and employing different types of classification methods. A careful analysis of the results provided sufficient evidence to respond appropriately to the open questions. The various evaluated scenarios and the drawn conclusions from the results shed light on the potentiality of the methods and on the challenges that fake news detection presents.

Towards automatically filtering fake news in Portuguese

The profitability promoted by Google in its brand new video distribution platform YouTube has attracted an increasing number of users. However, such success has also attracted malicious users, which aim to self-promote their videos or disseminate viruses and malwares. Since YouTube offers limited tools for comment moderation, the spam volume is shockingly increasing which lead owners of famous channels to disable the comments section in their videos. Automatic comment spam filtering on YouTube is a challenge even for established classification methods, since the messages are very short and often rife with slangs, symbols and abbreviations. In this work, we have evaluated several top-performance classification techniques for such purpose. The statistical analysis of results indicate that, with 99.9% of confidence level, decision trees, logistic regression, Bernoulli Naive Bayes, random forests, linear and Gaussian SVMs are statistically equivalent. Based on this, we have also offered the TubeSpam -- an accurate online system to filter comments posted on YouTube.

http://www.dt.fee.unicamp.br/~tiago/papers/TCA_ICMLA15.pdf

TubeSpam: Comment Spam Filtering on YouTube

A new classifier is presented to detect undesired short text comments.The proposed approach is light, fast, multinomial and offers incremental learning.The impact of applying text normalization and semantic indexing is studied.The results indicate the proposed techniques outperformed most of the approaches.Text normalization and semantic indexing enhanced the classifiers performance. The popularity and reach of short text messages commonly used in electronic communication have led spammers to use them to propagate undesired content. This is often composed by misleading information, advertisements, viruses, and malwares that can be harmful and annoying to users. The dynamic nature of spam messages demands for knowledge-based systems with online learning and, therefore, the most traditional text categorization techniques can not be used. In this study, we introduce the MDLText, a text classifier based on the minimum description length principle, to the context of filtering undesired short text messages. The proposed approach supports incremental learning and, therefore, its predictive model is scalable and can adapt to continuously evolving spamming techniques. It is also fast, with computational cost increasing linearly with the number of samples and features, which is very desirable for expert systems applied to real-time electronic communication. In addition to the dynamic nature of these messages, they are also short and usually poorly written, rife with slangs, symbols, and abbreviations that difficult text representation, learning, and filtering. In this scenario, we also investigated the benefits of using text normalization and semantic indexing techniques. We showed these techniques can improve the text content quality and, consequently, enhance the performance of the expert systems for spamming detection. Based on these findings, we propose a new hybrid ensemble approach that combines the predictions obtained by the classifiers using the original text samples along with their variations created by applying text normalization and semantic indexing techniques. It has the advantages of being independent of the classification method and the results indicated it is efficient to filter undesired short text messages.

Towards filtering undesired short text messages using an online learning approach with semantic indexing

Currently, a great volume of the available information on several websites comes from the interaction with users, such as social networks, forums and blogs, where readers can post comments and sometimes develop habits of frequenting them. Some blogs specialized in certain subjects, gain the users credibility and become references in the field. Nevertheless, the ease of inserting content through text comments makes room for unwanted messages, which affect the user experience, reduce the quality of the information provided by the websites and indirectly cause personal and economic losses. In this scenario, this paper presents a comprehensive study of established machine learning techniques applied to automatically detect undesired comments posted on blogs. Furthermore, different sets of attributes were evaluated along with text normalization techniques. Experiments carried out with a real and public database indicate that support vector machines, logistic regression and stacking ensemble methods, trained with both attributes extracted from the text messages and posting information, are promising for the task of blocking undesired comments.

Post or Block? Advances in Automatically Filtering Undesired Comments

A significant amount of the available information on web sites come from the interaction with users, such as news sites and blogs, where readers can post comments and sometimes develop habits of frequenting them. Some blogs specialize in certain subjects, receive the users credibility and become references in the field. However, the ease of inserting content through text comments makes room for unwanted messages, which affect the user experience, reduce the quality of the information provided by the websites and indirectly causing personal and economic losses. Given this scenario, this paper presents a comprehensive analysis of machine learning techniques applied to automatically detect undesired comments posted on blogs. Experiments carried out with a real and public database indicate that support vector machines and logistic regression, trained with both attributes extracted from the text messages and metadata from the posts, are promising in the task of filtering unwanted comments.

http://www.dt.fee.unicamp.br/~tiago/papers/ICMLA13_Almeida.pdf

Learning to Block Undesired Comments in the Blogosphere

Muitos usuarios do YouTube produzem conteudo regularmente e fazem desta tarefa seu principal meio de vida. Contudo, esse sucesso vem despertando a atencao de usuarios mal-intencionados, que propagam comentarios indesejados para se autopromoverem ou para disseminar links maliciosos. Neste cenario, metodos tradicionais de categorizacao de texto podem sofrer limitacoes devido as caracteristicas inerentes ao problema: (1) os comentarios costumam ser curtos e mal redigidos e (2) o problema de classificacao e naturalmente online. Este artigo avalia um metodo de classificacao baseado no principio da descricao mais simples e compara os resultados com os de metodos tradicionais de aprendizado online. Tambem e proposta uma tecnica ensemble, que combina os metodos de classificacao com diferentes tecnicas de processamento de linguagem natural. Os experimentos foram cuidadosamente realizados e a analise estatistica dos resultados indica que a tecnica proposta obteve desempenho superior ao obtido quando apenas os comentarios originais foram empregados.

/pdf/mdltext-e-indexacao-semantica-aplicados-na-deteccao-de-spam-608mehf3kx.pdf

Tulio C. Alberto

Papers

TubeSpam: Comment Spam Filtering on YouTube

Towards filtering undesired short text messages using an online learning approach with semantic indexing

Post or Block? Advances in Automatically Filtering Undesired Comments

Learning to Block Undesired Comments in the Blogosphere

MDLText e Indexação Semântica aplicados na Detecção de Spam nos Comentários do YouTube