Marianne Junger

Raphael Hoheisel, Tom Meurs, Jai Wientjes et al.

Cybercrime forums play a central role in the cybercrime ecosystem, serving as hubs for the exchange of illicit goods, services, and knowledge. Previous studies have explored the market and social structures of these forums, but less is known about the behavioral dynamics of users, particularly regarding participants' disclosure of criminal activity. This study provides the first large-scale assessment of crime disclosure patterns in a major cybercrime forum, analysing over 3.5 million posts from nearly 300k users. Using a three-level classification scheme (benign, grey, and crime) and a scalable labelling pipeline powered by large language models (LLMs), we measure the level of crime disclosure present in initial posts, analyse how participants switch between levels, and assess how crime disclosure behavior relates to private communications. Our results show that crime disclosure is relatively normative: one quarter of initial posts include explicit crime-related content, and more than one third of users disclose criminal activity at least once in their initial posts. At the same time, most participants show restraint, with over two-thirds posting only benign or grey content and typically escalating disclosure gradually. Grey initial posts are particularly prominent, indicating that many users avoid overt statements and instead anchor their activity in ambiguous content. The study highlights the value of LLM-based text classification and Markov chain modelling for capturing crime disclosure patterns, offering insights for law enforcement efforts aimed at distinguishing benign, grey, and criminal content in cybercrime forums.

Azqa Nadeem, Marianne Junger

Laptops have become an indispensable asset in today's digital age. They often contain highly sensitive information, such as credentials and confidential documents. As a result, the value of a laptop is an accumulation of the value of both the physical device itself and the cyber assets it contains, making it a lucrative target for theft. Educational institutions have a large population of potential victims of laptop theft. To mitigate this risk, we investigate whether a simple warning sign can reduce the opportunity for potential offenders. To this end, we have conducted an empirical study to observe the prevalence of students/staff leaving their laptops unattended at a university study hall at the Delft University of Technology in the Netherlands, both with and without a warning sign. We observed 148 out of 220 subjects leaving their laptops unattended in just three weeks. The results also showed that without the warning banner, 75.5% (83 out of 110) of subjects left their laptops unattended and with the warning, only 59.1% (65 out of 110) of subjects showed the same behavior, which is a significant reduction of 16.4%. In addition, a qualitative analysis was performed on the responses of subjects who left their laptops unattended after the warning banner was placed. The results showed a mix of convenience, and a blind trust on the safety of the faculty. In conclusion, a simple banner was effective in reducing the opportunity for laptop theft. However, the percentage of laptops left unattended was still high even after the introduction of the banner.