Description

A newly advanced macOS malware loader, known as ReaderUpdate, has exhibited significant adaptability by incorporating a variety of programming languages, including Nim, Rust, Go, Crystal, and Python. Active since at least 2020, this malware has largely evaded detection by security vendors due to its evolving implementation. Initially a compiled Python binary, ReaderUpdate has transitioned to alternative development languages to enhance stealth and optimize payload delivery. It is primarily distributed through freeware and third-party download sites, often concealed within trojanized utility apps such as DragonDrop. Once installed, it establishes persistence on the infected system and communicates with command-and-control (C2) servers to receive further instructions. While its primary payload has been the Genieo (DOLITTLE) adware, its modular design suggests it could deliver more severe threats in the future. The malware's infrastructure is extensive, utilizing multiple malicious domains such as entryway[.]world, airconditionersontop[.]com, and streamingleaksnow[.]com. These domains are interconnected across different malware iterations, indicating an actively maintained operation. Upon execution, ReaderUpdate collects system hardware details using macOS’s system_profiler command, generating a unique identifier for each compromised machine. It then verifies its installation path and, if necessary, establishes a dedicated folder structure to persist within the system. To ensure continued operation, the malware installs a LaunchAgent, allowing it to execute automatically upon login making it resistant to system reboots. The choice of lightweight, diverse programming languages suggests an intentional strategy to explore different evasion techniques and maintain compatibility across macOS versions. With the ability to execute arbitrary commands, ReaderUpdate poses a significant risk, particularly in Pay-Per-Install (PPI) and Malware-as-a-Service (MaaS) campaigns aimed at macOS users. Its modular architecture allows attackers to quickly adapt and deploy additional malware when needed. As macOS increasingly becomes a target for cybercriminals, security teams must enforce strict software download policies, enhance endpoint detection capabilities, and implement behavior-based monitoring to counter this growing threat. SentinelOne researchers emphasize that ReaderUpdate’s continued evolution underscores the increasing sophistication of macOS malware and the urgent need for layered security defenses.