A powerful cybercriminal tool known as Lumma Stealer has been disabled by Microsoft in a coordinated effort with international law enforcement agencies. The malware was responsible for infecting over 394,000 Windows computers worldwide between March and May 2025. This attack targeted individuals and organizations alike, stealing crucial data like login credentials, financial records, and cryptocurrency wallet details. Microsoft’s Digital Crimes Unit (DCU) led the investigation, effectively disrupting the malware’s operations and breaking down its network infrastructure. While the exact scale of impact remains unknown, the sheer scope of infections suggests a widespread attack. The company has declined to elaborate on specific methods of delivery but previously attributed Lumma Stealer’s deployment to compromised software packages or spam campaigns. The investigation is ongoing, with Microsoft expected to release further findings and updates.