A highly sophisticated malware operation is actively distributing the Grandoreiro banking trojan, targeting individuals in Mexico, Argentina, and Spain through deceptive phishing emails that mimic official tax authorities. The campaign begins with fraudulent government notifications warning recipients of substantial tax penalties, instilling a sense of urgency that prompts them to click on malicious links. These links direct users to counterfeit tax document portals hosted on virtual private servers, often utilizing subdomains resembling legitimate services, such as vmi2500240[.]contaboserver[.]net, to enhance credibility. Once victims interact with these links, they are led to a fraudulent website where clicking a "Download PDF" button initiates a series of redirects, culminating in the download of a password-protected ZIP file from Mediafire. This ZIP archive, secured with the password 2025, contains an obfuscated Visual Basic Script designed to obscure its true purpose. When executed, the script extracts another ZIP file into the victim’s Public directory, concealing a Delphi-compiled executable that is disguised with a PDF icon to avoid suspicion. Upon execution, the malware displays a fake Adobe Reader error message to deceive the user into believing a document failed to open. Meanwhile, it silently establishes persistence within the system and communicates with remote command-and-control servers via unconventional ports, such as port 42195. Grandoreiro is specifically engineered to harvest financial data, scanning for Bitcoin wallet directories and collecting system information, including language preferences and unique machine identifiers, through registry queries. This campaign underscores the increasing sophistication of cybercriminals who exploit legitimate hosting services and advanced obfuscation tactics to evade security defenses. Organizations must implement layered security strategies to detect and mitigate threats at every stage of the attack lifecycle from phishing email detection to payload execution monitoring and command-and-control traffic analysis.
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