WhatsApp malware campaign delivers VBScript and MSI backdoors

A malware campaign uses WhatsApp messages to deliver VBS scripts that initiate a multi-stage infection chain. The attack leverages renamed Windows tools and cloud-hosted payloads to install MSI backdoors and maintain persistent access to compromised systems. The post WhatsApp malware campaign delivers VBScript and MSI backdoors appeared first on Microsoft Security Blog .

In this article Attack chain overview Mitigation and protection guidance Hunting queries Indicators of compromise Microsoft Defender Experts observed a campaign beginning in late February 2026 that uses WhatsApp messages to deliver malicious Visual Basic Script (VBS) files. Once executed, these scripts initiate a multi-stage infection chain designed to establish persistence and enable remote access. The campaign relies on a combination of social engineering and living-off-the-land techniques.

It uses renamed Windows utilities to blend into normal system activity, retrieves payloads from trusted cloud services such as AWS, Tencent Cloud, and Backblaze B2, and installs malicious Microsoft Installer (MSI) packages to maintain control of the system. By combining trusted platforms with legitimate tools, the threat actor reduces visibility and increases the likelihood of successful execution.