DarkGram: Exploring and Mitigating Cybercriminal content shared in Telegram channels

We present the first large scale analysis of 339 cybercriminal activity channels (CACs) on Telegram from February to May 2024. Collectively followed by over 23.8 million users, these channels shared a wide array of illicit content, including compromised credentials, pirated software and media, tools for blackhat hacking resources such as malware, social engineering scams, and exploit kits. We developed DarkGram, a BERT based framework that identifies malicious posts from the CACs with an accuracy of 96%, using which we conducted a quantitative analysis of 53,605 posts from these channels, revealing key characteristics of shared content. While much of this content is distributed for free, channel administrators frequently employ promotions and giveaways to engage users and boost the sales of premium cybercriminal content. These channels also pose significant risks to their own subscribers. Notably, 28.1% of shared links contained phishing attacks, and 38% of executable files were bundled with malware. Moreover, our qualitative analysis of replies in CACs shows how subscribers cultivate a dangerous sense of community through requests for illegal content, illicit knowledge sharing, and collaborative hacking efforts, while their reactions to posts, including emoji responses, further underscore their appreciation for such content. We also find that the CACs can evade scrutiny by quickly migrating to new channels with minimal subscriber loss, highlighting the resilience of this ecosystem. To counteract this, we further utilized DarkGram to detect new channels, reporting malicious content to Telegram and the affected organizations which resulted in the takedown of 196 such channels over three months. To aid further collaborative efforts in taking down these channels, we open source our dataset and the DarkGram framework.