Detection of abusive language in user generated online content has become an issue of increasing importance in recent years. Most current commercial methods make use of blacklists and regular expressions, however these measures fall short when contending with more subtle, less ham-fisted examples of hate speech. In this work, we develop a machine learning based method to detect hate speech on online user comments from two domains which outperforms a state-of-the-art deep learning approach. We also develop a corpus of user comments annotated for abusive language, the first of its kind. Finally, we use our detection tool to analyze abusive language over time and in different settings to further enhance our knowledge of this behavior.

Many large Internet websites are accessed by users anonymously, without requiring registration or logging-in. However, to provide personalized service these sites build anonymous, yet persistent, user models based on repeated user visits. Cookies, issued when a web browser first visits a site, are typically employed to anonymously associate a website visit with a distinct user (web browser). However, users may reset cookies, making such association short-lived and noisy. In this paper we propose a solution to the cookie churn problem: a novel algorithm for grouping similar cookies into clusters that are more persistent than individual cookies. Such clustering could potentially allow more robust estimation of the number of unique visitors of the site over a certain long time period, and also better user modeling which is key to plenty of web applications such as advertising and recommender systems.

Unlabeled samples can be intelligently selected for labeling to minimize classification error. In many real-world applications, a large number of unlabeled samples arrive in a streaming manner, making it impossible to maintain all the data in a candidate pool. In this work, we focus on binary classification problems and study selective labeling in data streams where a decision is required on each sample sequentially. We consider the unbiasedness property in the sampling process, and design optimal instrumental distributions to minimize the variance in the stochastic process. Meanwhile, Bayesian linear classifiers with weighted maximum likelihood are optimized online to estimate parameters. In empirical evaluation, we collect a data stream of user-generated comments on a commercial news portal in 30 consecutive days, and carry out offline evaluation to compare various sampling strategies, including unbiased active learning, biased variants, and random sampling. Experimental results verify the usefulness of online active learning, especially in the non-stationary situation with concept drift.

Large scale retrieval of handwritten documents has primarily been focused around searching a query text in the OCR'ed transcription of the document images, which provides a limited view of the complete search process. Recent research advances have led to a number of content based retrieval techniques which expand the search scope to document content level (i.e. image features, meta-information). Based on similar motivations, we propose a new approach to content based retrieval of handwritten document images by retrieving similar handwriting styles corresponding to a handwritten query image. At the core, we formulate this problem as the task of unsupervised writer style classification without the need of any style definitions or grammar. We build upon our previous work in writer style modeling and apply it to learn a style distribution for every handwriting sample in the corpus. Given a query image, all documents are ranked in order of their style distribution similarity. Experimental results conducted on publicly available IAM dataset demonstrate the efficacy of our proposed method over baseline feature based systems.

In this paper we present a novel CAPTCHA that is based on the current hard AI problem of mixed-text (handwriting and printed-text) segmentation. The proposed CAPTCHA overlays generated handwritten word images on a generated printed-text background. We first propose a modification that allows for character level perturbations on an existing synthetic handwriting generation technique. These perturbations are parameterized allowing for varying levels of handwritten word complexity. We then use the output from the modified synthetic handwriting generator as the foreground for the mixed-text CAPTCHA. Experiments show that the proposed approach is effective at successfully distinguishing between humans and machines. Human recognition accuracy averages at 0.77 while machine accuracy is below 0.0001.

Cancelable biometric systems are gaining in popularity for use in person authentication for applications where the privacy and security of biometric templates are important considerations. A variety of approaches have been proposed in the literature. In this work, we have chosen two (a registration based and a registration free) techniques and performed a comparative study focusing on template representation size, useful dataset coverage, system accuracy and transform strength. Results show that both systems have their own advantages that are suited for use in specific applications.