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Microsoft has monitored Lumma Stealer, an infostealer malware used by financially motivated threat actors. Lumma Stealer, also known as LummaC2, functions as a malware-as-a-service (MaaS) solution that extracts data from browsers and applications, including cryptocurrency wallets. The entity behind Lumma is identified as Storm-2477, which maintains the malware and its command-and-control (C2) infrastructure. Affiliates can create malware binaries and manage C2 communications through a panel provided by Storm-2477. Ransomware groups have integrated Lumma Stealer into their operations. Lumma Stealer employs various delivery techniques, including phishing emails, malvertising, drive-by downloads, Trojanized applications, and abuse of legitimate services. Specific campaigns have been identified, such as one in April 2025 that used EtherHiding and ClickFix techniques to deliver Lumma Stealer via compromised websites. Another campaign on April 7, 2025, targeted Canadian organizations with emails containing invoice lures that led to malicious downloads. The malware is developed using C++ and ASM, employing advanced obfuscation techniques to evade detection. It can extract a wide range of user data, including browser credentials, cryptocurrency wallet information, and user documents. Lumma Stealer maintains a robust C2 infrastructure with multiple hardcoded and fallback C2 servers, utilizing encryption methods to secure communications. Microsoft's Digital Crimes Unit has disrupted Lumma Stealer's infrastructure by blocking approximately 2,300 malicious domains. Recommendations to mitigate the impact of Lumma Stealer include strengthening Microsoft Defender configurations, implementing multifactor authentication, and utilizing phishing-resistant authentication methods. Microsoft Defender products can detect and block activities associated with Lumma Stealer, providing alerts and insights for incident response.