Beyond App Markets: Demystifying Underground Mobile App Distribution Via Telegram

TL;DR

This paper explores the underground mobile app ecosystem on Telegram, revealing its prevalence, promotional strategies, and malicious behaviors, which pose significant challenges for content moderation and user safety.

Contribution

It provides the first comprehensive analysis of underground app distribution on Telegram, including a novel dataset and insights into their promotion and characteristics.

Findings

Underground apps on Telegram account for about 1% of its user base.

Apps mainly offer gambling and pornography services.

Sophisticated promotional networks and content moderation gaps are identified.

Abstract

Within the thriving mobile app ecosystem ecosystem, a subset of apps provides illicit services such as gambling and pornography to pursue economic gains, collectively referred to as "underground economy apps". While previous studies have examined these apps' characteristics and identification methods, investigations into their distribution via platforms beyond app markets (like Telegram) remain scarce, which has emerged as a crucial channel for underground activities and cybercrime due to the robust encryption and user anonymity. This study provides the first comprehensive exploration of the underground mobile app ecosystem on Telegram. Overcoming the complexities of the Telegram environment, we build a novel dataset and analyze the prevalence, promotional strategies, and characteristics of these apps. Our findings reveal the significant prevalence of these apps on Telegram, with the total sum of subscription user numbers across channels promoting these apps equivalent to 1% of Telegram's user base. We find these apps primarily cater to gambling and pornography services. We uncover sophisticated promotional strategies involving complex networks of apps, websites, users, and channels, and identify significant gaps in Telegram's content moderation capabilities. Our analysis also exposes the misuse of iOS features for app distribution and the prevalence of malicious behaviors in these apps. This research not only enhances our understanding of the underground app ecosystem but also provides valuable insights for developing effective regulatory measures and protecting users from potential risks associated with these covert operations. Our findings provide implications for platform regulators, app market operators, law enforcement agencies, and cybersecurity professionals in combating the proliferation of underground apps on encrypted messaging platforms.