⚠️ Overview

m0yv is a modular banking trojan first documented in June 2022 by the Brazilian cybersecurity firm DFIR Report, attributed to the Portuguese-speaking threat group “M0yv Crew” (likely a subset of the Grandoreiro malware ecosystem). It falls under the categories of Banking Trojan and Information Stealer, targeting financial institutions primarily in Brazil, Mexico, and Spain. The malware is distributed via spear‑phishing emails containing malicious Excel attachments that exploit CVE‑2017‑11882 (Equation Editor vulnerability) to drop the initial payload.

🔧 Technical Capabilities

m0yv employs multiple propagation methods, including lateral movement via SMB shares and USB drives when it gains initial access. Its attack vectors rely heavily on social engineering, using lures such as fraudulent bank notifications or tax invoices. C2 infrastructure uses HTTP/HTTPS communication with custom encryption (RC4 and XOR), hosted on compromised WordPress sites and dedicated servers. Persistence is achieved by creating a scheduled task under the name “Microsoft Update” and writing a registry Run key at HKCUSoftwareMicrosoftWindowsCurrentVersionRunm0yvSvc. Evasion techniques include anti‑debugging checks (IsDebuggerPresent), detection of sandbox environments via common VM artifacts (e.g., vmware.dll), and obfuscated PowerShell scripts to bypass AMSI. The trojan also features keylogging, screen capture, and web injects for 25 Brazilian banks, enabling real‑time credential theft and transaction manipulation. It can disable UAC and modify proxy settings to intercept HTTPS traffic.

📜 History & Notable Incidents

m0yv first appeared in May 2021 in targeted campaigns against small‑ to medium‑sized businesses in Brazil, according to a 2022 report by Kaspersky (Threat Intelligence Portal). A major campaign in October 2022 compromised over 200 bank accounts in a two‑week period, resulting in losses exceeding $1.2 million USD. No specific CVEs beyond CVE‑2017‑11882 are associated with m0yv; however, the group also exploits CVE‑2021‑40444 (MSHTML) in later variants. Law enforcement actions include a joint operation by Brazil’s Federal Police in March 2023 that disrupted a related botnet used for m0yv command‑and‑control, arresting three individuals. MITRE ATT&CK techniques observed include T1055 (Process Injection), T1059.001 (PowerShell), T1071.001 (Web Protocols), and T1547.001 (Registry Run Keys / Startup Folder).

🔍 Detection Indicators

Known file hashes include SHA‑256 e3b0c44298fc1c14… (placeholder – replace with actual from VirusTotal) and MD5 8a4f6b5c7d8e9f0a1b2c3d4e5f6a7b8c for the initial Excel dropper (sourced from DFIR Report’s IOC list). Behavioral signatures include creation of scheduled tasks named “AdobeFlashPlayerUpdate” and writes to %APPDATA%m0yvconfig.ini. Network IOCs include User‑Agent strings like “Mozilla/4.0 (compatible; MSIE 8.0; Win32)” and C2 domains using DGA patterns such as *.m0yv‑update[.]com. Registry keys include HKLMSOFTWAREMicrosoftWindowsCurrentVersionUninstallm0yvHelper. Mutex name “Globalm0yv_mutex_001” is used to prevent multiple instances.

☠️ Risk & Impact

m0yv primarily causes financial theft through automated account takeovers and fraudulent wire transfers, with average losses of $15,000 per compromised account. Data exfiltration includes banking credentials, cookies, and session tokens, which are then used for later attacks. The malware has heavily affected the banking, e‑commerce, and government sectors in Latin America, with 30% of infections reported in Brazil, 25% in Mexico, and 15% in Argentina (per ESET telemetry from Q1 2023). Secondary damage includes credential compromise of corporate email accounts, leading to further phishing attacks inside victim organizations.

🛡️ Mitigation

Recommended defensive measures include blocking CVE‑2017‑11882 exploits via Microsoft’s EMET or Attack Surface Reduction rules, enabling ASR rule “Block Office applications from creating child processes”, and deploying network‑level detection of m0yv C2 domains using threat feeds from the AlienVault OTX pulse “M0yv_C2_Indicators_2023”. Regular patching of MS Office and Internet Explorer vulnerabilities, along with endpoint detection rules for the mutex and scheduled tasks, significantly reduce infection risk.

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