Description

Cybersecurity analysts have discovered a highly sophisticated malware campaign aimed at WhatsApp users in Brazil. This operation employs a self-spreading worm that delivers malicious payloads designed to steal banking credentials and logins for cryptocurrency platforms. The attack was first observed on September 29, 2025, and marks a new level of complexity in social engineering, exploiting users' trust in familiar contacts to propagate malware across the WhatsApp Web platform. Victims receive deceptive messages that appear to come from trusted WhatsApp contacts who were previously infected. These messages include ZIP files labeled with names like “NEW-20251001_150505-XXX_XXXXXXX.zip” or Portuguese terms such as “ORCAMENTO” (Budget) and “COMPROVANTE” (Voucher) to increase their legitimacy. The instructions within the messages tell recipients to open the files on a computer, intentionally diverting them from mobile devices that may have stronger protections. Once opened, the ZIP file delivers a malicious Windows shortcut (LNK) file that initiates a multi-stage PowerShell infection sequence. Researchers at Sophos have observed this activity across over 400 client environments and more than 1,000 compromised systems. Subsequent stages of the attack attempt to weaken system defenses, including disabling Microsoft Defender exclusions and User Account Control, as stated in Portuguese-language comments within the code. This paves the way for deploying either an automated browser hijacker or a banking trojan known as Maverick, which actively monitors for access to Brazilian banks and crypto services. The malware is designed not only to steal credentials but also to replicate itself by messaging the victim’s WhatsApp contacts, increasing the rate of infection through trusted social connections. Experts suggest the campaign may be linked to earlier attacks using the Coyote trojan, and warn that platforms like WhatsApp Web are becoming prime targets due to their broad user base and lower mobile-level defenses. Maintaining strong endpoint protections and educating users about suspicious attachments remain key to mitigating these evolving threats.