Digital images and video footages comprise one of the core data types for human-machine interaction and visual understanding in general. Human perception along with the human logic are the most attractive capabilities of the human species that the research community strives to mimic. Except the relevant perception models, the community focused also on pioneer computer vision models that could extract additional information from visual representations towards facilitating various human activities. Object recognition, face detection, pedestrian detection, style transfer and weed detection are some research fields amongst a variety of applications that can be exploited to accomplish specific objectives. Our research activities display a wide diversity of computer vision objectives in order to cover a significant number of applications and extend the state-of-the-art in these research fields.
Fight against Crime and Terrorism
PROJECTS
PUBLICATIONS
- S. Bianchi, M. Mancuso, C. Paternoster, G. Kalpakis, T. Tsikrika, S. Vrochidis, D. Kozhuharova, and B. Jaeger. “Artificial Intelligence to counter Cyber-Terrorism. ” in Proceedings International Conference on Cybersecurity and Cybercrime, 5-7 December 2023, Vol. 10
- D. Touska, K. Gkountakos, O. Theodosiadou, T. Tsikrika, S. Vrochidis, "Object Detection and Recognition in Visual Content Understanding", CERTH, Thessaloniki, Greece, Tech. Rep. INFINITY project H2020, 2023.
- Theodosiadou, O.; Koufakis, A.-M.; Tsikrika, T.; Vrochidis, S.; Kompatsiaris, I. Change Point Analysis of Time Series Related to Bitcoin Transactions: Towards the Detection of Illegal Activities. J. Risk Financial Manag. 2023, 16, 408. https://doi.org/10.3390/jrfm16090408 OPEN ACCESS
- A. Konstantinou, D. Chatzakou, O. Theodosiadou, T. Tsikrika, S. Vrochidis and I. Kompatsiaris, “Trend Detection in Crime-related Time Series with Change Point Detection Methods” in International Conference of the Cross-Language Evaluation Forum for European Languages, 18-21 September 2023, Thessaloniki, Greece. Arampatzis, A., et al. Experimental IR Meets Multilinguality, Multimodality, and Interaction. CLEF 2023. Lecture Notes in Computer Science, vol 14163. Springer. https://doi.org/10.1007/978-3-031-42448-9_7 OPEN ACCESS
- D. Touska, K. Gkountakos, K. Ioannidis, T. Tsikrika, S. Vrochidis and I. Kompatsiaris, "Graph-Based Data Association in Multiple Object Tracking: A Survey", 2023, In Proceedings of the 29th International Conference on Multimedia Modeling (MMM 2023), 9 - 12 January 2023, Bergen, Norway. OPEN ACCESS
- K. Stavrothanasopoulos, K. Gkountakos, K. Ioannidis, T. Tsikrika, S. Vrochidis, I. Kompatsiaris, "Vehicle Color Identification Framework using Pixel-level Color Estimation from Segmentation Masks of Car Parts". Fifth IEEE International Conference on Image Processing, Applications and Systems (IPAS 2022), 07-09 December, 2022, Genova, Italy. OPEN ACCESS
- O. Theodosiadou, D. Chatzakou, T. Tsikrika, S. Vrochidis, I. Kompatsiaris, “Real-time Threat Assessment based on Hidden Markov Models”, Risk Analysis 2023, vol. 43, no. 10, pp. 2069-2081, October 2023, https://doi.org/10.1111/risa.14105.
- K. Gkountakos, D. Galanopoulos, D. Touska, K. Ioannidis, S. Vrochidis, V. Mezaris, I. Kompatsiaris, “ITI-CERTH participation in ActEV and AVS Tracks of TRECVID 2022”, Proc. TRECVID 2022 Workshop, Gaithersburg, MD, USA, 6 Dec. 2022. OPEN ACCESS
- A-M. Koufakis, T. Tsikrika, S. Vrochidis, I. Kompatsiaris, “M4D-MKLab/ITI-CERTH Participation in TREC Deep Learning Track 2022” in Proc. Text REtrieval Conference (TREC) 2022 Workshop, Gaithersburg, MD, USA, 14-18 Nov. 2022. OPEN ACCESS
- R. Karlović, H. Nitsch, S. E. Fikenscher, D. Osterman, S. Menexis, T. Tsikrika, S. Vrochidis, I. Kompatsiaris,and A. Sahar (2022). "The Threat of Behavioral Radicalization Online: Conceptual Challenges and Technical Solutions Provided by the PROPHETS (Preventing Radicalization Online through the Proliferation of Harmonized ToolkitS) Project". In G. Markarian, R. Karlovic, H. Nitsch and K. Chandramouli (eds.) Security Technologies and Social Implications: A European Perspective. (accepted for publication).
- G. Begkas, P. Giannakeris, K. Ioannidis, G. Kalpakis, T. Tsikrika, S. Vrochidis, I. Kompatsiaris. “Automatic Visual Recognition of Unexploded Ordnances Using Supervised Deep Learning” in Proceedings of the 2022 International Conference on Multimedia Retrieval, Newark, NJ, USA, June 27-30, 2022, pp. 286-294, DOI:https://doi.org/10.1145/3512527.3531383.
- K. Pantelidou, D. Chatzakou, T. Tsikrika, S. Vrochidis, I. Kompatsiaris. "Selective Word Substitution for Contextualized Data Augmentation". In Proc. of the 27th International Conference on Natural Language & Information Systems (NLDB), Valencia, Spain, 15-17 June 2022, pp.508-516. OPEN ACCESS
- P. Kyriakidis, D. Chatzakou, T. Tsikrika, S. Vrochidis, I. Kompatsiaris, "Leveraging Transformer Self Attention Encoder for Crisis Event Detection in Short Texts", 44th European Conference on Information Retrieval (ECIR2022), Stavanger, Norway, April 10–14, 2022, Proceedings, Part II Apr 2022, pp. 163–171. DOI:https://doi.org/10.1007/978-3-030-99739-7_19. OPEN ACCESS
- K. Gkountakos, D. Galanopoulos, D. Touska, K. Ioannidis, S. Vrochidis, V. Mezaris, I. Kompatsiaris, "ITI-CERTH participation in ActEV and AVS Tracks of TRECVID 2021" in Proc. TRECVID 2021 Workshop, Gaithersburg, MD, USA (Virtual), 2021. OPEN ACCESS
- A-Μ Koufakis, T. Tsikrika, S. Vrochidis, & I. Kompatsiaris, "M4D-MKLab/ITI-CERTH Participation in TREC Deep Learning Track 2021". Text REtrieval Conference (TREC). OPEN ACCESS
- O. Theodosiadou, K. Pantelidou, N. Bastas, D. Chatzakou, T. Tsikrika, S. Vrochidis, I. Kompatsiaris, "Change Point Detection in Terrorism-Related Online Content Using Deep Learning Derived Indicators". Information 2021, 12, 274. OPEN ACCESS
- Κ. Gkountakos, D. Touska, K. Ioannidis, T. Tsikrika, S. Vrochidis, & I. Kompatsiaris. "Spatio-temporal activity detection and recognition in untrimmed surveillance videos". In Proceedings of the 2021 International Conference on Multimedia Retrieval, August 2021. OPEN ACCESS
- G. Galanakis,; X.Zabulis,; T.Evdaimon,;S.-E. Fikenscher,; S.Allertseder,; T.Tsikrika,; S. Vrochidis "A Study of 3D Digitisation Modalities for Crime Scene Investigation". Forensic. Sci. 2021, 1, 56–85. OPEN ACCESS
- C. Iliou, T. Kostoulas, T. Tsikrika, V. Katos, S. Vrochidis, and I. Kompatsiaris, "Web Bot Detection Evasion Using Generative Adversarial Networks", In Proceedings of the 2021 IEEE International Conference on Cyber Security and Resilience, IEEE, 26-28 July, 2021. DOI:10.1109/CSR51186.2021.9527915. OPEN ACCESS
- C. Iliou, T. Kostoulas, T. Tsikrika, V. Katos, S. Vrochidis, I. Kompatsiaris. "Detection of advanced web bots by combining web logs with mouse behavioural biometrics". Digital Threats: Research and Practice (DTRAP), 2021, Volume 2, Issue 3, 3 September 2021, DOI:10.1145/3447815. OPEN ACCESS
- K. Gkountakos, K. Ioannidis, T. Tsikrika, S. Vrochidis, I. Kompatsiaris. "Visual Recognition of Abnormal Activities in Video Streams". In Technology Development for Security Practitioners (pp. 151-165). Cham: Springer International Publishing. OPEN ACCESS
- K. Gkountakos, K. Ioannidis, T.Tsikrika, S. Vrochidis, & Ι. Kompatsiaris, "Crowd Violence Detection from Video Footage". In 2021 International Conference on Content-Based Multimedia Indexing (CBMI). IEEE June 2021. OPEN ACCESS
- B. Akhgar, M. Gercke, S. Vrochidis, H. Gibson (2021). Dark Web investigation. 288 Pages, Springer.
- K. Gkountakos, D. Galanopoulos, M. Mpakratsas, D. Touska, A. Moumtzidou, K. Ioannidis, I. Gialampoukidis, S. Vrochidis, V. Mezaris, I. Kompatsiaris, "ITI-CERTH participation in TRECVID 2020", Proc. TRECVID 2020 Workshop, Gaithersburg, MD, USA, Dec. 2020. OPEN ACCESS
- G. Orfanidis, K. Ioannidis, A. Tefas, S. Vrochidis, Y. Kompatsiaris, "A modified Single-Shot multibox Detector for beyond Real-Time Object Detection", 25th International Conference on Pattern Recognition, (ICPR 2020), 10 & 15 January 2021, Milan, Italy.
- D. Chatzakou, J. Soler-Company, T. Tsikrika, L. Wanner, S. Vrochidis, I. Kompatsiaris, "User Identity Linkage in Social Media Using Linguistic and Social Interaction Features", In Proceedings of the 2020 ACM on Web Science Conference, (WEBSCI 2020), July 6-10 2020. OPEN ACCESS
- K. Gkountakos, K. Ioannidis, T. Tsikrika, S. Vrochidis, I. Kompatsiaris,"A Crowd Analysis Framework for Detecting Violence Scenes", in Proceedings of the 2020 International Conference on Multimedia Retrieval (ICMR ‘20), June 8–11, 2020, Dublin, Ireland. OPEN ACCESS
- A. Koufakis, D. Chatzakou, G. Meditskos, T. Tsikrika, S. Vrochidis, I. Kompatsiaris, "Semantic Web Technologies in Fighting Crime and Terrorism: The CONNEXIONs Approach", Invited talk in 1st International Workshop on IoT infrastructures for safety in pervasive environments (IoT4SAFE), 2 June, 2020. OPEN ACCESS
- K. Gkountakos, K. Ioannidis, S. Vrochidis, I. Kompatsiaris, "ITI-CERTH participation in TRECVID 2019", Proc. TRECVID 2019 Workshop, Gaithersburg, MD, USA, Nov. 2019. OPEN ACCESS
- A. Katmada, G. Kalpakis, T. Tsikrika, S. Vrochidis & Y. Kompatsiaris, "An extensible framework for interactive real-time visualizations of large-scale heterogeneous multimedia information from online sources", in Proceedings of the International Conference on Multimedia Modeling (MMM2020), Special Session on “Multimedia Analytics: Perspectives, Tools and Applications”, Daejeon, Korea, 5-8 January 2020.
- S. Andreadis, A. Moumtzidou, K. Apostolidis, K. Gkountakos, D. Galanopoulos, E. Michail, I. Gialampoukidis, S. Vrochidis, V. Mezaris, I. Kompatsiaris, "VERGE in VBS 2020", Proc. 26th Int. Conf. on Multimedia Modeling (MMM2020), 5-8 January 2020, Daejeon Convention Center (DCC), Korea OPEN ACCESS
- N. Bastas, G. Kalpakis, T. Tsikrika, S. Vrochidis & Y. Kompatsiaris, "A comparative study of clustering methods using word embeddings", in Proceedings of the 2019 European Intelligence and Security Informatics Conference (EISIC 2019), Oulu, Finland, 24-26 November 2019. https://ieeexplore.ieee.org/document/9108898
- P. Panagiotou, G. Kalpakis, T. Tsikrika, S. Vrochidis, I. Kompatsiaris. "Query reformulation based on word embeddings: A comparative study". Technology Advances and Support for Security Practitioners of the Security Informatics and Law Enforcement book series. OPEN ACCESS
- P. Mitzias, E. Kontopoulos, J. Staite, T. Day, G. Kalpakis, T. Tsikrika, H. Gibson, S. Vrochidis, B. Akhgar, & Υ. Kompatsiaris, "Deploying Semantic Web Technologies for Information Fusion of Terrorism related Content and Threat Detection on the Web", Proceedings of the Security Analytics and Cyber Threat Intelligence on the Web (SACTI 2019) workshop, in conjunction with the IEEE/WIC/ACM International Conference on Web Intelligence (WI 2019), Thessaloniki, Greece, 14-17 October 2019. OPEN ACCESS
- C. Iliou, T. Kostoulas, T. Tsikrika, V. Katos, S. Vrochidis, and Y. Kompatsiaris, "Towards a framework for detecting advanced Web bots", Iin Proceedings of the 14th International Conference on Availability, Reliability and Security, p. 18. ACM, 2019. OPEN ACCESS
- I. Gialampoukidis, S. Vrochidis, I. Kompatsiaris, and I. Antoniou. “Probabilistic density-based estimation of the number of clusters using the DBSCAN-martingale process”. Pattern Recognition Letters, Vol. 123, pp 23-30, 4 March 2019. OPEN ACCESS
- G. Kalpakis, T. Tsikrika, S. Vrochidis, I. Kompatsiaris, "Identifying terrorism-related key actors in multidimensional social networks", in Proc. 25th Int. Conf. on Multimedia Modeling (MMM2019), Thessaloniki, Greece, Jan. 2019. OPEN ACCESS
- C. Iliou, T. Tsikrika, G. Kalpakis, S. Vrochidis, I. Kompatsiaris, "Adaptive focused crawling using online learning: A study on content related to Islamic extremism", in 5th International conference ‘Internet Science’ (INSCI’2018), 24-26 October 2018, St. Petersburg, Russia. OPEN ACCESS
- G. Kalpakis, T. Tsikrika, I. Gialampoukidis, S. Papadopoulos, S. Vrochidis, I., Kompatsiaris, "Analysis of Suspended Terrorism-Related Content on Social Media", Community-Oriented Policing and Technological Innovations, 107-118. OPEN ACCESS
- G. Kalpakis, T. Tsikrika, I. Gialampoukidis, S. Papadopoulos, S. Vrochidis, I. Kompatsiaris. "Analysis of Suspended Terrorism-Related Content on Social Media". In Community-Oriented Policing and Technological Innovations, Springer Briefs in Policing, Springer, 27 April 2018. OPEN ACCESS
- C. Iliou, G. Kalpakis, T. Tsikrika, S. Vrochidis, I. Kompatsiaris. "Hybrid Focused Crawling on the Surface and the Dark Web". EURASIP Journal on Information Security, vol. 2017, no. 11, 4 July 2017. OPEN ACCESS
- M. Zampoglou, S. Vrochidis, A. Rocha, V. Katos (Eds.). (2017). MFSec '17: Proceedings of the 2nd International Workshop on Multimedia Forensics and Security. Bucharest, Romania, 2017. Association for Computing Machinery, 30 June 2017. OPEN ACCESS
- B. Akhgar, P. Bertrand, C. Chalanouli, T. Day, I. Fragkiadakis, H. Gibson, D. Kavallieros, E. Kermitsis, I. Kompatsiaris, E. Kyriakou, G. Leventakis, E. Lissaris, S. Mille, D. Myttas, T. Tsikrika, S. Vrochidis, U. Williamson. "TENSOR: Retrieval and Analysis of Heterogeneous Online Content for Terrorist Activity Recognition". Proceedings of the Estonian Academy of Se-curity Sciences: Secure Societies, 15 June 2017. OPEN ACCESS
- I. Gialampoukidis, G. Kalpakis, T. Tsikrika, S. Papadopoulos, S. Vrochidis, I. Kompatsiaris, "Detection of Terrorism-related Twitter Communities using Centrality Scores", in Proceedings of International Workshop on Multimedia Forensics and Security (MFSec 2017), Bucharest, Romania, June 06, 2017. OPEN ACCESS
- T. Tsikrika, B. Akhgar, V. Katos, S. Vrochidis, P. Burnap, M. L. Williams, "1st International Workshop on Search and Mining Terrorist Online Content & Advances in Data Science for Cyber Security and Risk on the Web". In Proceedings of the Tenth ACM International Conference on Web Search and Data Mining (WSDM 2017), pp. 823-824, Cambridge, UK, February 2017. OPEN ACCESS
- G. Kalpakis, T. Tsikrika, N. Cunningham, C. Iliou, S. Vrochidis, J. Middleton, I. Kompatsiaris. "OSINT and the Dark Web". In Open Source Intelligence Investigation - From Strategy to Implementation, B. Akhgar, P. S. Bayerl, F. Sampson (Eds.), Springer, 3 January 2017. OPEN ACCESS
- I. Gialampoukidis, T. Tsikrika, S. Vrochidis, I. Kompatsiaris,"Community Detection in Complex Networks Based on DBSCAN* and a Martingale Process", in 11th International Workshop on Semantic and Social Media Adaptation and Personalization (SMAP), 2016, pp. 1-6. IEEE.
- C. Iliou, G. Kalpakis, T. Tsikrika, S. Vrochidis, I. Kompatsiaris,"Hybrid Focused Crawling for Homemade Ex-plosives Discovery on Surface and Dark Web", 11th International Conference on Availability, Reliability and Security (ARES 2016), Salzburg, Austria, Aug 2016. DOI: 10.1109/ARES.2016.66
- I. Gialampoukidis, G. Kalpakis, T. Tsikrika, S. Vrochidis, I. Kompatsiaris,"Key player identification in terrorism-related social media networks using centrality measures", in Intelligence and Security Informatics Conference (EISIC), 2016 European, pp. 112-115. IEEE, 2016. DOI: 10.1109/EISIC.2016.029
- G. Kalpakis, T. Tsikrika, C. Iliou, T. Mironidis, S. Vrochidis, J. Middleton, U. Williamson, I. Kompatsiaris,"In-teractive Discovery and Retrieval of Web Resources Containing Home Made Explosive Recipes", in 4th International Conference on Human Aspects of Information Security, Privacy and Trust, Toronto, Canada, 17 - 22 July 2016.
- T. Tsikrika, G. Kalpakis, S. Vrochidis, I. Kompatsiaris, I. Paraskakis, I. Kavasidis, J. Middleton, and U. Williamson, "A Framework for the Discovery, Analysis, and Retrieval of Multimedia Homemade Explosives Information on the Web", in Proceedings of the International Workshop on Multimedia Forensics and Security (MFSec 2015), held in conjunction with the 10th International Conference on Availability, Reliability and Security, Toulouse, France, 2015. https://doi.org/10.1109/ARES.2015.86
- G. Kalpakis, T. Tsikrika, F. Markatopoulou, N. Pittaras, S. Vrochidis, V. Mezaris, I. Patras, and I. Kompatsiaris, "Concept Detection on Multimedia Web Resources about Home Made Explosives", in Proceedings of the International Workshop on Multimedia Forensics and Security (MFSec 2015), held in conjunction with the 10th International Conference on Availability, Reliability and Security, Toulouse, France, 2015. DOI: 10.1109/ARES.2015.85