Astaroth Trojan Hijacks WhatsApp Web Sessions to Spread Banking Malware to Contacts
The operators of the banking Trojan Astaroth, also known as Guildma, have equipped infected Windows machines with the ability to autonomously distribute malicious archives through WhatsApp Web. Victims now face not only the risk of banking data theft but also the possibility of unknowingly forwarding the Trojan to their own contacts, according to researchers at CrowdStrike.
Previously, Astaroth spread mainly through phishing emails. In late 2025 the operators added a dedicated spam module for WhatsApp Web. The module copies the profile of Chrome or Edge, downloads the official WebDriver, and launches the browser in headless mode. It then attaches to an already authenticated WhatsApp Web session using the legitimate WPPConnect/WA-JS library.
From the user’s perspective the process remains silent. In the background the bot iterates through the address book and sends three messages to every contact: a time-appropriate greeting, a ZIP archive containing the Astaroth loader, and a closing text. Links and wording are randomized to avoid pattern-based detection.
Because the messages arrive from a known person and begin with natural phrases such as “good morning,” recipients are far more likely to open the attachment. The spam-bot code shares structural and functional traits with tools used by other Latin American groups, including Vareg, indicating either a common developer or active sharing of components within the regional cybercrime ecosystem.
Observable signs of infection include PowerShell downloads of WebDriver, the appearance of ChromeAuto_ folders under C:\Users\Public\Temp, headless Chromium processes, and network connections to WPPConnect components. Astaroth has effectively turned WhatsApp Web into a delivery service for its banking payload, with the victim unknowingly covering the distribution costs.
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