Detecting sexual predators in chats using behavioral features and imbalanced learning
Abstract
This paper presents a system developed for detecting sexual predators in online chat conversations using a two-stage classification and behavioral features. A sexual predator is defined as a person who tries to obtain sexual favors in a predatory manner, usually with underage people. The proposed approach uses several text categorization methods and empirical behavioral features developed especially for the task at hand. After investigating various approaches for solving the sexual predator identification problem, we have found that a two-stage classifier achieves the best results. In the first stage, we employ a Support Vector Machine classifier to distinguish conversations having suspicious content from safe online discussions. This is useful as most chat conversations in real life do not contain a sexual predator, therefore it can be viewed as a filtering phase that enables the actual detection of predators to be done only for suspicious chats that contain a sexual predator with a very high degree. In the second stage, we detect which of the users in a suspicious discussion is an actual predator using a Random Forest classifier. The system was tested on the corpus provided by the PAN 2012 workshop organizers and the results are encouraging because, as far as we know, our solution outperforms all previous approaches developed for solving this task.
Integrity signals
Registry
Cites
Statistics
Claims the paper makes
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
Some papers attempted to consider this setting and have tried to address this as an imbalanced data problem.
“Some papers attempted to consider this setting and have tried to address this as an imbalanced data problem [62,72,73,86].”
From Online grooming detection: A comprehensive survey of child exploitation in chat logs (2023) · cites this paper as [62]
The cost-sensitive technique performed best when testing on the PAN2012 dataset for predator detection, where a cost matrix defines the penalty for misclassifying a sample.
“The cost-sensitive technique performed best when testing on the PAN2012 dataset for predator detection, where a cost matrix defines the penalty for misclassifying a sample.”
From Online grooming detection: A comprehensive survey of child exploitation in chat logs (2023) · cites this paper as [62]
The necessity of pertinent data leads to the challenge of a highly imbalanced dataset in grooming detection, where the amount of predatory conversations data is much lower than everyday conversations data.
“The necessity of pertinent data also leads to the challenge of the highly imbalanced dataset in grooming detection, where the amount of predatory conversations data is much lower than everyday conversations data [62,72,85].”
From Online grooming detection: A comprehensive survey of child exploitation in chat logs (2023) · cites this paper as [62]
Cites
Breiman, L. (2001) · Machine Learning · doi:10.1023/a:1010933404324 · Cited by 133,538 · see citing works
Elements of Information Theory
Cover, T. M., & Thomas, J. A. (2001) · Wiley eBooks · doi:10.1002/0471200611 · Cited by 37,139 · see citing works
(2003) · Journal of Machine Learning Research · doi:10.5555/944919.944937 · Cited by 32,337 · see citing works
The WEKA data mining software: an update
Hall, M., Frank, E., Holmes, G., Pfahringer, B., Reutemann, P., & Witten, I. H. (2009) · ACM SIGKDD Explorations Newsletter · doi:10.1145/1656274.1656278 · Cited by 17,750 · see citing works
Blei, D. M., Ng, A. Y., & Jordan, M. I. (2002) · The MIT Press eBooks · doi:10.7551/mitpress/1120.003.0082 · Cited by 12,649 · see citing works
Introduction to information retrieval
(2009) · Choice Reviews Online · doi:10.5860/choice.46-2715 · Cited by 12,278 · see citing works
Introduction to Information Retrieval
Manning, C. D., Raghavan, P., & Schütze, H. (2008) · doi:10.1017/cbo9780511809071 · Cited by 11,288 · see citing works
He, H., & Garcia, E. A. (2009) · IEEE Transactions on Knowledge and Data Engineering · doi:10.1109/tkde.2008.239 · Cited by 10,359 · see citing works
Flesch, R. (1948) · Journal of Applied Psychology · doi:10.1037/h0057532 · Cited by 5,391 · see citing works
(1998) · Cited by 2,679 · see citing works
Exploratory Undersampling for Class-Imbalance Learning
Liu, X., Wu, J., & Zhou, Z. (2008) · IEEE Transactions on Systems Man and Cybernetics Part B (Cybernetics) · doi:10.1109/tsmcb.2008.2007853 · Cited by 2,477 · see citing works
Elements of Information Theory
Nalewajski, R. F. (2011) · Springer eBooks · doi:10.1007/978-3-642-20180-6_8 · Cited by 2,310 · see citing works
Linguistic Inquiry and Word Count (LIWC)
Chung, C. K., & Pennebaker, J. W. (2012) · IGI Global eBooks · doi:10.4018/978-1-60960-741-8.ch012 · Cited by 2,152 · see citing works
Cost-sensitive boosting for classification of imbalanced data
Sun, Y., Kamel, M. S., Wong, A. K. C., & Wang, Y. (2007) · Pattern Recognition · doi:10.1016/j.patcog.2007.04.009 · Cited by 1,429 · see citing works
The Victimization of Children and Youth: A Comprehensive, National Survey
David Finkelhor, B., Ormrod, R. K., Turner, H. A., & Hamby, S. L. (2004) · Child Maltreatment · doi:10.1177/1077559504271287 · Cited by 1,411 · see citing works
Domingos, P. (1999) · ACM SIGKDD Conference on Knowledge Discovery and Data Mining (KDD) · doi:10.1145/312129.312220 · Cited by 1,307 · see citing works
Class imbalances versus small disjuncts
Jo, T., & Japkowicz, N. (2004) · ACM SIGKDD Explorations Newsletter · doi:10.1145/1007730.1007737 · Cited by 687 · see citing works
Wolak, J., Finkelhor, D., Mitchell, K. J., & Ybarra, M. L. (2008) · American Psychologist · doi:10.1037/0003-066x.63.2.111 · Cited by 537 · see citing works
Learning When Data Sets are Imbalanced and When Costs are Unequal and Unknown
Maloof, M. A. (2003) · Cited by 406 · see citing works
Wolak, J., David Finkelhor, B., & Mitchell, K. J. (2004) · Journal of Adolescent Health · doi:10.1016/j.jadohealth.2004.05.006 · Cited by 303 · see citing works
A review of online grooming: Characteristics and concerns
Whittle, H., Hamilton-Giachritsis, C., Beech, A., & Collings, G. (2013) · Aggression and Violent Behavior · doi:10.1016/j.avb.2012.09.003 · Cited by 242 · see citing works
Cambria, E., & Hussain, A. (2012) · SpringerBriefs in Cognitive Computation · doi:10.1007/978-94-007-5070-8 · Cited by 236 · see citing works
Youth Internet Users at Risk for the Most Serious Online Sexual Solicitations
MITCHELL, K., FINKELHOR, D., & WOLAK, J. (2007) · American Journal of Preventive Medicine · doi:10.1016/j.amepre.2007.02.001 · Cited by 230 · see citing works
Liar, liar! An examination of how open, supportive and honest people are in chat rooms
Whitty, M. T. (2002) · Computers in Human Behavior · doi:10.1016/s0747-5632(01)00059-0 · Cited by 158 · see citing works
Malesky, L. A. (2007) · Journal of Child Sexual Abuse · doi:10.1300/j070v16n02_02 · Cited by 128 · see citing works
Overview of the International Sexual Predator Identification Competition at PAN-2012.
Inches, G., & Crestani, F. (2012) · Cited by 93 · see citing works
Proceedings of the 13th European Conference on Artificial Intelligence
Madsen, A. L. (1998) · Cited by 74 · see citing works
Proceedings of the 2nd Workshop on Computational Approaches to Subjectivity and Sentiment Analysis
Balahur, A., Montoyo, A., Martínez-Barco, P., & Boldrini, E. (2011) · Cited by 68 · see citing works
A Two-step Approach for Effective Detection of Misbehaving Users in Chats
Villatoro-Tello, E., Juárez-González, A., Escalante, H. J., Montes-y-Gómez, M., & Villaseñor-Pineda, L. (2012) · Cited by 41 · see citing works
Criminal network investigation
Wiil, U. K. (2014) · Security Informatics · doi:10.1186/2190-8532-3-1 · Cited by 35 · see citing works
Kernel Methods and String Kernels for Authorship Analysis.
Popescu, M., & Grozea, C. (2012) · Fraunhofer-Publica (Fraunhofer-Gesellschaft) · Cited by 32 · see citing works
A Learning-Based Approach for the Identification of Sexual Predators in Chat Logs.
Parapar, J., Losada, D. E., & Barreiro, Á. (2012) · CLEF (Online Working Notes/Labs/Workshop) · Cited by 27 · see citing works
Sexual predator detection in chats with chained classifiers
Escalante, H. J., Villatoro-Tello, E., Juárez, A. G.-U., Montes-y-Gómez, M., & Villaseñor-Pineda, L. (2013) · Cited by 24 · see citing works
Conversation Level Constraints on Pedophile Detection in Chat Rooms
Peersman, C., Vaassen, F., Asch, V. V., & Daelemans, W. M. P. (2012) · Bristol Research (University of Bristol) · Cited by 23 · see citing works
Identifying Sexual Predators by SVM Classification with Lexical and Behavioral Features.
Morris, C. W., & Hirst, G. (2012) · Cited by 23 · see citing works
Gillam, L., & Vartapetiance, A. (2012) · Surrey Research Insight Open Access (The University of Surrey) · Cited by 20 · see citing works
Identifying Predators Using ChatCoder 2.0.
Kontostathis, A., Garron, A., Reynolds, K., West, W. H., & Edwards, L. (2012) · CLEF (Online Working Notes/Labs/Workshop) · Cited by 14 · see citing works
"Our Little Secret": pinpointing potential predators
Vartapetiance, A., & Gillam, L. (2014) · Security Informatics · doi:10.1186/s13388-014-0003-7 · Cited by 11 · see citing works
Features for Modelling Characteristics of Conversations.
Eriksson, G., & Jussi Karlgren, C. (2012) · CLEF (Online Working Notes/Labs/Workshop) · Cited by 10 · see citing works
Flagged first, then by citations
2 of the 41 references couldn’t be matched to a known paper.
Cited by
Sorted by citations
Cyber-aggression, Cyberbullying, and Cyber-grooming: A Survey and Research Challenges
Mladenović, M., Ošmjanski, V., & Stanković, S. V. (2022) · ACM Computing Surveys · doi:10.1145/3424246 · Cited by 79 · see citing works
Early detection of deception and aggressiveness using profile-based representations
Escalante, H. J., Villatoro-Tello, E., Garza, S. E., López-Monroy, A. P., Montes-y-Gómez, M., & Villaseñor-Pineda, L. (2017) · Expert Systems with Applications · doi:10.1016/j.eswa.2017.07.040 · Cited by 44 · see citing works
Online grooming detection: A comprehensive survey of child exploitation in chat logs
Borj, P. R., Raja, K., & Bours, P. (2023) · Knowledge-Based Systems · doi:10.1016/j.knosys.2022.110039 · Cited by 38 · see citing works
Milon-Flores, D. F., & Cordeiro, R. L. F. (2022) · Knowledge-Based Systems · doi:10.1016/j.knosys.2021.108017 · Cited by 29 · see citing works
The Detection of Sexual Harassment and Chat Predators Using Artificial Neural Network
Hamzah, N. A., & Dhannoon, B. N. (2021) · Karbala International Journal of Modern Science · doi:10.33640/2405-609x.3157 · Cited by 18 · see citing works
Early Detection of Sexual Predators in Chats
Vogt, M., Leser, U., & Akbik, A. (2021) · doi:10.18653/v1/2021.acl-long.386 · Cited by 18 · see citing works
Sexual-predator Detection System based on Social Behavior Biometric (SSB) Features
Wani, M. A., Agarwal, N., & Bours, P. (2021) · Procedia Computer Science · doi:10.1016/j.procs.2021.05.075 · Cited by 18 · see citing works
Chiang, E., Nguyen, D., Towler, A., Haas, M., & Grieve, J. (2021) · International Journal of Speech Language and the Law · doi:10.1558/ijsll.41446 · Cited by 13 · see citing works
Automatically Identifying Online Grooming Chats Using CNN-based Feature Extraction
Preuß, S., Bley, L. P., Bayha, T., Dehne, V., Jordan, A., Reimann, S., Roberto, F., Zahm, J. R., Siewerts, H., Labudde, D., et al. (2021) · Cited by 13 · see citing works
Milon-Flores, D. F. (2022) · doi:10.11606/d.55.2022.tde-01082022-150335 · Cited by 12 · see citing works
Detecting Sexual Predatory Chats by Perturbed Data and Balanced Ensembles
Borj, P. R., Raja, K., & Bours, P. (2021) · 2021 International Conference of the Biometrics Special Interest Group (BIOSIG) · doi:10.1109/biosig52210.2021.9548303 · Cited by 13 · see citing works
Effectiveness of machine learning methods in detecting grooming: a systematic meta-analytic review
Bianchi, M. L., Castillo, N., Astudillo, C. A., & Ahumada-Méndez, F. (2025) · Scientific Reports · doi:10.1038/s41598-024-83003-4 · Cited by 13 · see citing works
Machine learning approaches to detect online harassment using bag of words
Hamzah, N. A., & Dhannoon, B. N. (2023) · AIP conference proceedings · doi:10.1063/5.0118599 · Cited by 7 · see citing works
Reconceptualising ‘risk’: Towards a humanistic paradigm of sexual offending
McAlinden, A. (2021) · Social & Legal Studies · doi:10.1177/09646639211032957 · Cited by 6 · see citing works
Prevention of Emotional Entrapment of Children on Social Media
Kirupalini, S., Baskar, A., Ramesh, A., Rengarajan, G., Gowri, S., Swetha, S., & Sangeetha, D. (2021) · International Conference on Emerging Techniques in Computational Intelligence (ICETCI) · doi:10.1109/icetci51973.2021.9574068 · Cited by 4 · see citing works
Waezi, H., Barzegar, R., & Fani, H. (2024) · ACM International Conference on Information and Knowledge Management (CIKM) · doi:10.1145/3627673.3679974 · Cited by 2 · see citing works
dos Santos, L. F., & Guedes, G. P. (2019) · Anais do Brazilian Workshop on Social Network Analysis and Mining (BraSNAM) · doi:10.5753/brasnam.2019.6556 · Cited by 1 · see citing works
dos Santos, L. F., & Guedes, G. P. (2020) · iSys - Brazilian Journal of Information Systems · doi:10.5753/isys.2020.822 · Cited by 1 · see citing works
SafeCon: AI-Powered Real-Time Cyber Grooming Detection System
Sallahudin, S., Ismail, M., Ali, S., Ahmed, A., & Hameed, M. F. (2025) · VFAST Transactions on Software Engineering · doi:10.21015/vtse.v13i2.2118
The Missing Resources for Child Online Risk Detection
Prosser, E., Peersman, C., & Edwards, M. (2026) · ACM Computing Surveys · doi:10.1145/3806384
- Authors
- CARDEI, C., & REBEDEA, T.
- Affiliations
- Universitatea Națională de Știință și Tehnologie Politehnica București (RO)
- ORCID
- REBEDEA, TRAIAN
- Venue
- Natural Language Engineering
- Publisher
- Cambridge University Press (CUP)
- Published
- 2017-01-31
- Volume
- 23
- Issue
- 4
- Pages
- 589-616
- ISSN
- 1351-3249 (ISSN-L)
- 1469-8110
- OpenAlex
- W2585232420
- Cited by
- 21
- References
- 41
- Citations by year
- 2026: 1 · 2025: 2 · 2024: 1 · 2023: 1 · 2022: 2 · 2021: 11 · 2020: 1 · 2019: 1 · 2017: 1
- FWCI
- 0.49
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Natural Language Engineering (publishedVersion)
- Topics
- Physical Sciences › Computer Science › Artificial Intelligence › Hate Speech and Cyberbullying Detection
- Physical Sciences › Computer Science › Artificial Intelligence › Text and Document Classification Technologies
- Physical Sciences › Computer Science › Information Systems › Spam and Phishing Detection
- Keywords
- child sexual exploitation, behavioral characteristics, imbalanced learning, two-stage classification, text classification, support vector machine, random forest
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
What counts as a claim ›How we measure confidence ›How we check this ›
Are you an author, or do you see a problem with this page? Request a review