Astaroth Trojan Hijacks WhatsApp Web Sessions to Spread Banking Malware to Contacts

The operators of the Astaroth banking Trojan, also known as Guildma, have added a new module that turns infected Windows systems into automated spam bots for WhatsApp Web. The malware copies browser profiles from Chrome or Edge, launches a legitimate WebDriver instance, and connects to an already authenticated WhatsApp Web session using the WPPConnect/WA-JS library. Once active, the bot scans the victim's contact list and sends each recipient a personalized greeting, a ZIP archive containing the Astaroth loader, and a closing message, all generated with randomized phrasing to evade detection. The technique leverages the trust users place in messages from known contacts, significantly increasing the likelihood of successful infection. Researchers at CrowdStrike note code similarities with tools used by other Latin American groups, including Vareg, suggesting shared development or active exchange of components. Indicators of compromise include PowerShell downloads of WebDriver, creation of ChromeAuto_ folders in C:\Users\Public\Temp, headless Chromium execution, and network activity tied to WPPConnect components.

AntiMalwareJuly 31, 2026Translated from Russian

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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.

CrowdStrike Astaroth Guildma WPPConnect Vareg

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