[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$f-8Z0M9AKodXyU7qLX72nIgudTWIZYETOgmHTwlaV7_c":3},{"article":4,"iocs":52},{"id":5,"title":6,"slug":7,"summary":8,"ai_summary":9,"brief":10,"full_text":11,"url":12,"image_url":13,"published_at":14,"ingested_at":15,"relevance_score":16,"entities":17,"category_id":34,"category":35,"article_tags":39},"63725788-5026-4396-a632-5d7b1fc7aa67","Microsoft Takes Down Malware-Signing Service Behind Ransomware Attacks","microsoft-takes-down-malware-signing-service-behind-ransomware-attacks-2b1be7","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","Microsoft disrupted a malware-signing-as-a-service (MSaaS) operation run by Fox Tempest, which weaponized Microsoft's Artifact Signing system. This service allowed cybercriminals to sign malware as legitimate software, enabling ransomware and other attacks. Microsoft seized the threat actor's website and infrastructure.","Microsoft disrupted a malware-signing-as-a-service operation called Fox Tempest.","Microsoft Takes Down Malware-Signing Service Behind Ransomware Attacks Ravie LakshmananMay 20, 2026Malware \u002F Cybercrime 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, said. Microsoft noted that the operation enabled the deployment of Rhysida ransomware by threat actors such as Vanilla Tempest, along with other malware families like Oyster, Lumma Stealer, and Vidar, illustrating the crucial role played by Fox Tempest within the cybercrime ecosystem. In addition, connections have been uncovered between the threat actor and affiliates associated with several prominent ransomware strains, including INC, Qilin, BlackByte, and Akira. Attacks mounted by these operations have targeted healthcare, education, government, and financial services located across the U.S., France, India, and China. Artifact Signing (formerly Azure Trusted Signing) is Microsoft's fully managed, end-to-end signing solution that allows developers to easily build and distribute applications, while ensuring that the software is legitimate and hasn't been modified by unauthorized parties. Fox Tempest is said to have leveraged this mechanism to generate short-lived, fraudulent code-signing certificates and use them to deliver trusted, signed malware and slip past security controls. The certificates were valid for only 72 hours. \"To obtain legitimate signed certificates through Artifact Signing, the requestor must pass detailed identify validation processes in keeping with industry standard verifiable credentials (VC), which suggests the threat actor very likely used stolen identities based in the United States and Canada to masquerade as a legitimate entity and obtain the necessary digital credentials for signing,\" Microsoft explained. \"The SignSpace website was built on Artifact Signing and enabled secure file signing through an admin panel and user page, leveraging Azure subscriptions, certificates, and a structured database for managing users and files.\" The service allowed paying cybercriminal customers to upload malicious files for code-signing using certificates fraudulently obtained by Fox Tempest. This, in turn, allowed malware and ransomware to masquerade as legitimate software like AnyDesk, Microsoft Teams, PuTTY, and Cisco Webex. The service cost between $5,000 and $9,000. Starting February 2026, the threat actor is said to have shifted to providing customers with pre-configured virtual machines (VMs) hosted on Cloudzy, thereby making it possible to directly upload the necessary artifacts to the attacker-controlled infrastructure and receive signed binaries in return. \"This infrastructure evolution reduced friction for customers, improved operational security for Fox Tempest, and further streamlined the delivery of malicious but trusted, signed malware at scale,\" Microsoft said. Threat actors like Vanilla Tempest have been found to distribute binaries signed through the service via legitimately purchased advertisements that redirected users searching for Microsoft Teams to bogus download pages, paving the way for the deployment of Oyster (aka Broomstick or CleanUpLoader), a modular implant and loader that's responsible for delivering Rhysida ransomware. Microsoft said Fox Tempest has continually adapted its tradecraft as the company enacted countermeasures, such as disabling fraudulent accounts and revoking the illicitly obtained certificates, with the threat actor even attempting to shift to a different code-signing service. Court documents reveal that Microsoft worked with a \"cooperative source\" to purchase and test the service between February and March 2026. \"When attackers can make malicious software look legitimate, it undermines how people and systems decide what's safe,\" Redmond said. \"Disrupting that capability is key to raising the cost of cybercrime.\" Found this article interesting? Follow us on Google News, Twitter and LinkedIn to read more exclusive content we post. SHARE     Tweet Share Share Share SHARE  Cloud security, code signing, Cybercrime, cybersecurity, digital Certificate, Malware, Microsoft, ransomware ⚡ Top Stories This Week Claude Mythos AI Finds 10,000 High-Severity Flaws in Widely Used Software Megalodon GitHub Attack Targets 5,561 Repos with Malicious CI\u002FCD Workflows ThreatsDay Bulletin: Linux Rootkits, Router 0-Day, AI Intrusions, Scam Kits and 25 New Stories Microsoft Warns of Two Actively Exploited Defender Vulnerabilities 9-Year-Old Linux Kernel Flaw Enables Root Command Execution on Major Distros GitHub Internal Repositories Breached via Malicious Nx Console VS Code Extension GitHub Breached — Employee Device Hack Led to Exfiltration of 3,800+ Internal Repos Microsoft Releases Mitigation for YellowKey BitLocker Bypass CVE-2026-45585 Exploit DirtyDecrypt PoC Released for Linux Kernel CVE-2026-31635 LPE Vulnerability ⚡ Weekly Recap: Exchange 0-Day, npm Worm, Fake AI Repo, Cisco Exploit and More Ivanti, Fortinet, SAP, VMware, n8n Patch RCE, SQL Injection, Privilege Escalation Flaws MiniPlasma Windows 0-Day Enables SYSTEM Privilege Escalation on Fully Patched Systems NGINX CVE-2026-42945 Exploited in the Wild, Causing Worker Crashes and Possible RCE Making Vulnerable Drivers Exploitable Without Hardware - The BYOVD Perspective The New Phishing Click: How OAuth Consent Bypasses MFA Developer Workstations Are Now Part of the Software Supply Chain ⭐ Featured Resources Claim ANY.RUN Anniversary Offer for Faster Malware Analysis [Guide] Learn to Detect AI Typosquatting Risks in Your Domain [Guide] Get Key Identity Security Insights From 2026 Snapshot Discover How to Navigate the Era of Constant Cyber Exposure","https:\u002F\u002Fthehackernews.com\u002F2026\u002F05\u002Fmicrosoft-takes-down-malware-signing.html","https:\u002F\u002Fblogger.googleusercontent.com\u002Fimg\u002Fb\u002FR29vZ2xl\u002FAVvXsEgiypJnCUStqk0SRgnT6bFPLXM9F10uUBgEZgGScKH8lNthkNnD4zP2-CBNIvo2eukKJzGKOs7RFjIq1KmR-pIGFT3pFS1wgz8ySDW7O9OaMkAHXSaZvHSP_Y2JxqGgkdbCLXcn-VZOYwirKa9gU7FqEZXDafHhgxupVx6cuJam1wsnjq3qjz7q36GlvirT\u002Fs1600\u002Fwindows-ransomware.jpg","2026-05-20T14:36:44+00:00","2026-05-20T16:00:17.26589+00:00",9,[18,21,23,26,29,31],{"name":19,"type":20},"Fox Tempest","threat_actor",{"name":22,"type":20},"Vanilla Tempest",{"name":24,"type":25},"OpFauxSign","campaign",{"name":27,"type":28},"Artifact Signing","product",{"name":30,"type":28},"Microsoft Teams",{"name":32,"type":33},"Microsoft","vendor","e7b231c8-5f79-4465-8d38-1ef13aea5a14",{"id":34,"icon":36,"name":37,"slug":38},null,"Threat Intelligence","threat-intelligence",[40,45,50],{"category":41},{"id":42,"icon":36,"name":43,"slug":44},"7d8b5ab8-ea0b-4ced-ae97-ec251b86993a","Ransomware","ransomware",{"category":46},{"id":47,"icon":36,"name":48,"slug":49},"89f78b1c-3503-45a1-9fc7-e23d2ce1c6d5","Malware","malware",{"category":51},{"id":34,"icon":36,"name":37,"slug":38},[53,57,60,63,65],{"type":54,"value":55,"context":56},"domain","signspace[.]cloud","Fox Tempest's website",{"type":49,"value":58,"context":59},"Rhysida","Ransomware deployed via the service",{"type":49,"value":61,"context":62},"Oyster","Malware deployed via the service",{"type":49,"value":64,"context":62},"Lumma Stealer",{"type":49,"value":66,"context":62},"Vidar"]