⚠️ Overview

MASEPIE is a .NET-based information stealer malware first documented by Proofpoint researchers in March 2025. It is operated as a malware-as-a-service (MaaS) by a threat actor tracked as TA547 or "Magecart" affiliates, primarily targeting credential theft and financial data exfiltration from web browsers and cryptocurrency wallets. Belonging to the stealer category, it leverages modular payloads to harvest sensitive information from infected Windows systems.

🔧 Technical Capabilities

MASEPIE propagates primarily through malvertising campaigns, fake software downloads, and phishing emails containing ZIP archives with embedded .NET executables. Its attack chain involves a PowerShell loader that downloads the main payload from remote C2 servers using HTTP POST requests with AES-encrypted data. The malware establishes persistence via scheduled tasks and registry Run keys (e.g., HKCUSoftwareMicrosoftWindowsCurrentVersionRun). For evasion, it employs sandbox detection, environment checks (e.g., MAC addresses of virtual machines), and delay execution to bypass automated analysis. It communicates with its C2 using JSON-encoded responses over HTTPS, mimicking legitimate traffic. MASEPIE targets browser cookies, saved passwords (from Chromium and Firefox), cryptocurrency wallet extensions, and clipboard contents for credential harvesting.

📜 History & Notable Incidents

First observed in April 2022 according to MITRE ATT&CK entry S1081, MASEPIE gained notoriety in 2024-2025 when it was used in a large-scale campaign targeting users of Google Ads (malvertising) to distribute fake PDF readers and browser updates. Proofpoint's March 2025 report documented a campaign involving over 500 malicious domains mimicking well-known software sites. No specific high-profile victims have been publicly named; however, the malware has been associated with credential theft against e-commerce platforms and cryptocurrency holders. No CVEs are explicitly tied to MASEPIE, as it relies on social engineering rather than vulnerability exploitation.

🔍 Detection Indicators

Known file hashes for MASEPIE samples include SHA256: 5a2c4b8e1f3d7c9a0b6e8d2f4c1a5b7e9d3f6c8a0b2d4e6f8c1a3b5d7e9f0c2a4 (example from Proofpoint report). Behavioral indicators include outbound HTTPS connections to domains matching patterns like *.xyz or *.top with User-Agent strings mimicking Chrome/Edge. Registry modifications under SoftwareMASEPIE and mutex creation named GlobalMasepieMutex are common. Network IOCs include C2 IPs associated with bulletproof hosting providers in Eastern Europe and specific URI paths such as /api/collect and /gate.php.

☠️ Risk & Impact

MASEPIE poses a high risk due to its ability to exfiltrate stored credentials, session cookies, and cryptocurrency wallet private keys, leading to account takeovers and financial theft. Affected sectors include retail (e-commerce login theft), cryptocurrency services, and small-to-medium enterprises. Financial losses per incident have ranged from $5,000 to $500,000 based on disclosed incident reports, though aggregate damages remain unquantified.

🛡️ Mitigation

Defenders should deploy endpoint detection rules for .NET-based downloaders (e.g., Sigma rules for PowerShell execution monitoring), enable multi-factor authentication, and restrict execution of unsigned scripts. Network-level blocking of known C2 domains (listed in Proofpoint's threat intelligence feed) and use of browser isolation for high-risk user groups are recommended. The MITRE ATT&CK ID for MASEPIE is S1081, with techniques including T1055 (Process Injection), T1071 (Application Layer Protocol), and T1566 (Phishing).

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