George Kalpakis

The Centre for Research and Technology, Hellas · Information Technologies Institute (ITI)

This work proposes a framework integrating AI technologies and tools to assist micro and small hosting service providers (HSPs) in adhering to the terrorist content online (TCO) Regulation. The framework encompasses: (i) a suite of AI tools for the automated detection and removal of TCO, (ii) a federated learning infrastructure for (re-)training an...

In the era of ever-growing online social networking communities, reports of online crimes of various forms and targeting are growing exponentially, highlighting the imperative need for the development and enforcement of solutions and measures aimed at early detection and prevention. Specifically, in today’s landscape, child sexual abuse (CSA) and e...

Formulating effective queries for retrieving domain-specific content from the Web and social media is very important for practitioners in several fields, including law enforcement analysts involved in terrorism-related investigations. Query reformulation aims at transforming the original query in such a way, so as to increase the search effectivene...

This work presents the user-centered design and development of a generic and extensible visualization framework that can be re-used in various scenarios in order to communicate large–scale heterogeneous multimedia information obtained from social media and Web sources, through user-friendly interactive visualizations in real-time. Using the particu...

The Web and social media nowadays play an increasingly significant role in spreading terrorism-related propaganda and content. In order to deploy counterterrorism measures, authorities rely on automated systems for analysing text, multimedia, and social media content on the Web. However, since each of these systems is an isolated solution, investig...

Identifying terrorism-related key actors in social media is of vital significance for law enforcement agencies and social media organizations in their effort to counter terrorism-related online activities. This work proposes a novel framework for the identification of key actors in multidimensional social networks formed by considering several diff...

Social media are widely used by terrorist organizations and extremist groups for disseminating propaganda and recruiting new members. Given the recent pledges both by the major social media platforms and governments towards combating online terrorism, our work aims at understanding the terrorism-related content posted on social media and distinguis...

Focused crawlers enable the automatic discovery of Web resources about a given topic by automatically navigating through the Web link structure and selecting the hyperlinks to follow by estimating their relevance to the topic of interest. This work proposes a generic focused crawling framework for discovering resources on any given topic that resid...

Social media are widely used among terrorists to communicate and disseminate their activities. User-to-user interaction (e.g. mentions, follows) leads to the formation of complex networks, with topology that reveals key-players and key-communities in the terrorism domain. Both the administrators of social media platforms and Law Enforcement Agencie...

Monitoring terrorist groups and their suspicious activities in social media is a challenging task, given the large amounts of data involved and the need to identify the most influential users in a smart way. To this end, many efforts have focused on using centrality measures for the identification of the key players in terrorism-related social medi...

This work proposes a generic focused crawling framework for discovering resources on any given topic that reside on the Surface or the Dark Web. The proposed crawler is able to seamlessly traverse the Surface Web and several darknets present in the Dark Web (i.e. Tor, I2P and Freenet) during a single crawl by automatically adapting its crawling beh...

This work investigates the effectiveness of a novel interactive search engine in the context of discovering and retrieving Web resources containing recipes for synthesizing Home Made Explosives (HMEs). The discovery of HME Web resources both on Surface and Dark Web is addressed as a domain-specific search problem; the architecture of the search eng...

The Dark Web, a part of the Deep Web that consists of several darknets (e.g. Tor, I2P, and Freenet), provides users with the opportunity of hiding their identity when surfing or publishing information. This anonymity facilitates the communication of sensitive data for legitimate purposes, but also provides the ideal environment for transferring inf...

This work investigates the effectiveness of a state-of-the-art concept detection framework for the automatic classification of multimedia content, namely images and videos, embedded in publicly available Web resources containing recipes for the synthesis of Home Made Explosives (HMEs), to a set of predefined semantic concepts relevant to the HME do...

This work proposes a novel framework that integrates diverse state-of-the-art technologies for the discovery, analysis, retrieval, and recommendation of heterogeneous Web resources containing multimedia information about homemade explosives (HMEs), with particular focus on HME recipe information. The framework corresponds to a knowledge management...