Description

Massive phishing and malware campaign targeting Brazil is rapidly spreading through compromised WhatsApp Web sessions, Python-based automation, and an in-memory banking trojan. This Water-Saci activity abuses open-source WhatsApp automation tools to spread to a victim’s contacts. VBS, Python, AutoIt, and JavaScript components used to evade detection, harvest browser artifacts, and deliver a stealthy banking trojan tailored to Brazilian financial institutions and crypto wallets. Starting with a phishing email containing an obfuscated VBS file inside a ZIP archive. Once executed, the script decodes itself using charcode and XOR techniques, then downloads and launches both an MSI installer and a second-stage VBS that deploys Python, Selenium, ChromeDriver, and the whats.py module, which steals browser session data and recreates the victim’s WhatsApp Web session without requiring re-authentication. This module injects a helper JavaScript file, harvests contacts through undocumented WhatsApp Web APIs, and sends a sequence of messages along with the Base64-encoded malware payload, all transmitted from memory to avoid disk-based AV detection. Contact lists, logs, and delivery results are then sent to an attacker-controlled PHP C2. In parallel, the MSI deploys an AutoIt loader, encrypted payload files, and persistence mechanisms. AutoIt script collects extensive system information, checks for Brazilian banking software, identifies security products, and monitors active windows for targeted banking and crypto applications. On matching, it decrypts and decompresses the banking trojan entirely in memory, reflectively loads the PE, and injects it into svchost.exe. The payload then steals credentials and session data and exfiltrates them over IMAP, masking malicious traffic within legitimate email protocols. Mitigation requires blocking malicious ZIP/VBS attachments, restricting script execution, monitoring for Selenium or unauthorized ChromeDriver use, and detecting in-memory loading activity. Organizations should strengthen email filtering, enforce MFA for banking access, deploy behavioral threat protection, and ensure rapid investigation of unexpected WhatsApp Web activity or unexplained outbound messaging.