{"description":"Trending threats, MITRE ATT\u0026CK coverage, and detection metadata. Fed continuously.","feed_url":"https://feed.craftedsignal.io/products/microsoft-artifact-signing/feed.json","home_page_url":"https://feed.craftedsignal.io/","items":[{"_cs_actors":["Fox Tempest"],"_cs_cpes":[],"_cs_cves":[],"_cs_exploited":false,"_cs_has_poc":false,"_cs_poc_references":[],"_cs_products":["Microsoft Artifact Signing","Azure"],"_cs_severities":["high"],"_cs_tags":["malware-signing","azure","defense-evasion","ransomware"],"_cs_type":"threat","_cs_vendors":["Microsoft"],"content_html":"\u003cp\u003eMicrosoft disrupted a cybercrime service named Fox Tempest, which has been operating a malware-signing-as-a-service (MSaaS) since at least September 2025. This service abuses Microsoft Artifact Signing to generate short-lived code-signing certificates, which are then used to sign malware, disguising it as legitimate software and helping it evade detection. Fox Tempest has created over a thousand certificates and established hundreds of Azure tenants and subscriptions to support its operations. Microsoft has revoked over one thousand code-signing certificates attributed to Fox Tempest. The MSaaS has been used by several ransomware groups, including Vanilla Tempest (targeted in October 2025), and has delivered ransomware families such as Rhysida, Inc, Qilin, and Akira, as well as malware families like Lumma Stealer, Oyster, and Vidar.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eFox Tempest establishes fraudulent Azure tenants and subscriptions to support its operations.\u003c/li\u003e\n\u003cli\u003eThe actor abuses Microsoft Artifact Signing to generate short-lived code-signing certificates.\u003c/li\u003e\n\u003cli\u003eCybercriminals purchase the malware-signing-as-a-service.\u003c/li\u003e\n\u003cli\u003eMalware is signed with the fraudulently obtained certificates.\u003c/li\u003e\n\u003cli\u003eSigned malware is disguised as legitimate software.\u003c/li\u003e\n\u003cli\u003eVictims are tricked into downloading and executing the signed malware.\u003c/li\u003e\n\u003cli\u003eMalware executes, potentially leading to ransomware deployment or information theft.\u003c/li\u003e\n\u003cli\u003eStolen data is exfiltrated, or systems are encrypted and held for ransom.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eThe downstream impact of Fox Tempest\u0026rsquo;s operations has resulted in attacks against a broad range of industry sectors, including healthcare, education, government, and financial services, impacting organizations globally including, but not limited to, the United States, France, India, and China. The service costs thousands of dollars, and Microsoft believes the threat actor made millions. Successful attacks lead to data theft, system compromise, and financial losses.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eMonitor for unusual Azure tenant and subscription creation activity, which may indicate attempts to establish infrastructure for similar MSaaS operations.\u003c/li\u003e\n\u003cli\u003eEnable and review logs for Microsoft Artifact Signing and code-signing certificate generation events to identify potential abuse.\u003c/li\u003e\n\u003cli\u003eDeploy the Sigma rules in this brief to your SIEM to detect suspicious process execution and file creation activity associated with malware signed by certificates potentially linked to Fox Tempest.\u003c/li\u003e\n\u003cli\u003eBlock execution of known malware hashes (if available from other sources) to prevent initial compromise.\u003c/li\u003e\n\u003c/ul\u003e\n","date_modified":"2026-05-19T16:07:44Z","date_published":"2026-05-19T16:07:44Z","id":"https://feed.craftedsignal.io/briefs/2026-05-fox-tempest-msaas-disruption/","summary":"Microsoft disrupted Fox Tempest, a threat actor running a malware-signing-as-a-service (MSaaS) that abuses Microsoft Artifact Signing to generate short-lived code-signing certificates used to sign malware disguised as legitimate software, delivering ransomware and various information stealers to victims across multiple sectors.","title":"Fox Tempest Malware-Signing-as-a-Service Disrupted by Microsoft","url":"https://feed.craftedsignal.io/briefs/2026-05-fox-tempest-msaas-disruption/"}],"language":"en","title":"CraftedSignal Threat Feed — Microsoft Artifact Signing","version":"https://jsonfeed.org/version/1.1"}