Latin American businesses have been under attack by a sophisticated Windows-based banking trojan called TOITOIN since May 2023, according to Zscaler researchers.
Furthermore, the campaign follows a multi-staged infection chain, utilizing specially crafted modules that perform malicious activities, including code injection, User Account Control circumvention, and sandbox evasion.
The attack begins with phishing emails containing a link to a ZIP archive hosted on an Amazon EC2 instance, employing invoice-themed lures to deceive recipients. The trojan, injected into the “svchost.exe” process, enables further manipulation of system files and execution of commands with elevated privileges.
At the same time, TOITOIN demonstrates a well-crafted attack sequence with its six-stage endeavor. The downloader executable within the ZIP archive sets up persistence, generates a Batch script for system reboot, and communicates with a remote server to retrieve next-stage payloads.
The payloads include a valid signed binary that sideloads a rogue DLL, enabling the injection of malicious code into the “explorer.exe” process and bypassing User Account Control if necessary. TOITOIN has the capability to collect system information, harvest data from web browsers, and detect Topaz Online Fraud Detection.
Additionally, the command-and-control (C2) server’s response nature is currently unknown as it is no longer available. The threat actors behind the campaign employ deceptive phishing emails, intricate redirect mechanisms, and domain diversification to deliver their malicious payload.
The use of custom-developed modules with evasion techniques and encryption methods emphasizes the advanced nature of this multi-staged infection chain.
