05-20-2026, 03:05 PM
Microsoft on Tuesday said it disrupted a malware-signing-as-a-service (MSaaS) operation that weaponized the company's Artifact Signing system to deliver malicious code and conduct ransomware and other attacks, compromising thousands of machines and networks across the world.
The tech giant attributed the activity to a threat actor it calls Fox Tempest, which it said offered the MSaaS scheme to allow cybercriminals to disguise malware as legitimate software. The threat actor has been active since May 2025. The seizure effort has been codenamed OpFauxSign.
"To disrupt the service, we seized Fox Tempest's website signspace[.]cloud, took offline hundreds of the virtual machines running the operation, and blocked access to a site hosting the underlying code," Steven Masada, assistant general counsel at Microsoft's Digital Crimes Unit
The tech giant attributed the activity to a threat actor it calls Fox Tempest, which it said offered the MSaaS scheme to allow cybercriminals to disguise malware as legitimate software. The threat actor has been active since May 2025. The seizure effort has been codenamed OpFauxSign.
"To disrupt the service, we seized Fox Tempest's website signspace[.]cloud, took offline hundreds of the virtual machines running the operation, and blocked access to a site hosting the underlying code," Steven Masada, assistant general counsel at Microsoft's Digital Crimes Unit