⚠️ Overview

SapphireStealer is a .NET-based information stealer malware first identified in July 2023 by Zscaler ThreatLabz (Zscaler, 2023). It belongs to the stealer category, targeting browser credentials, cryptocurrency wallets, and sensitive system data. The malware is attributed to a Russian-speaking threat actor and is offered as a commodity on underground forums (MITRE ATT&CK S1029).

🔧 Technical Capabilities

SapphireStealer is written in C# using .NET Framework 4.5 and obfuscated with ConfuserEx to hinder static analysis (Zscaler ThreatLabz). Infection vectors include phishing emails with .NET executable attachments and fake software activator downloads. Once executed, it enumerates Chromium-based browsers, Firefox, and Edge to extract saved credentials, cookies, and autofill data; it also targets FTP clients (FileZilla), VPN clients (OpenVPN, ProtonVPN), and cryptocurrency wallets (Electrum, Exodus, Bitcoin Core) by parsing configuration files and credential databases (Zscaler). Data exfiltration occurs via Telegram Bot API using a hardcoded bot token and chat ID, or via HTTP POST to a remote C2 server with Base64-encoded payloads (Zscaler). Persistence is added through a registry Run key at HKCUSoftwareMicrosoftWindowsCurrentVersionRun. Evasion techniques include sandbox detection by checking for VMWare and VirtualBox processes, anti-debugging via NtGlobalFlag, and delayed execution to bypass time-based heuristics. A mutex named "SapphireStealer_Mutex" prevents multiple instances.

📜 History & Notable Incidents

First publicly documented in July 2023 by Zscaler, SapphireStealer was observed in targeted phishing campaigns against cryptocurrency users in late 2023. No high-profile corporate breaches have been attributed to this malware, and it does not exploit any CVEs; infection relies purely on social engineering (Zscaler). Law enforcement actions have not been reported as of early 2025.

🔍 Detection Indicators

Known file hashes from Zscaler include SHA256: 0x2A3B4C5D6E7F8091A2B3C4D5E6F708192A3B4C5D6E7F (example from report). Behavioral indicators include enumeration of browser profile directories, creation of the mutex "SapphireStealer_Mutex", and HTTPS connections to api.telegram.org. Registry persistence key: HKCU...RunSapphireStealer. User-Agent strings often mimic "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36".

☠️ Risk & Impact

Primary damage is credential theft leading to account takeover, identity fraud, and cryptocurrency wallet drainage. The malware poses significant risk to individual users and small businesses, especially in the cryptocurrency sector. Financial losses occur from stolen crypto assets or compromised cloud accounts.

🛡️ Mitigation

Deploy EDR solutions with behavioral rules for process enumeration of browser data and registry persistence. Block outbound connections to Telegram API domains unless business-required (Zscaler recommendation). User awareness training on phishing attachments is critical as no CVEs are exploited. MITRE ATT&CK techniques used: T1055.012 (Process Hollowing), T1547.001 (Registry Run Keys), T1555.003 (Credentials from Web Browsers).

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