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MostereRAT Malware Disables Security Tools, Targets Japanese Windows Users

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📰 2 unique sources, 2 articles

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A new malware campaign, tracked as MostereRAT, targets Japanese Windows users with sophisticated evasion techniques. MostereRAT disables antivirus and endpoint defenses, uses an obscure programming language, and abuses legitimate remote access tools to maintain persistent control over compromised systems. The malware's capabilities include privilege escalation, keylogging, data exfiltration, and the creation of hidden administrator accounts. The campaign's long-term objectives and the full extent of its impact remain unclear. MostereRAT employs Easy Programming Language (EPL) to evade detection and uses Windows Filtering Platform (WFP) filters to block security telemetry. The malware deploys legitimate remote access tools like AnyDesk, TigerVNC, and TightVNC, making it difficult to detect. The campaign highlights the importance of removing local administrator privileges and blocking unapproved remote access tools to reduce the attack surface. The malware uses mutual TLS (mTLS) to secure command-and-control (C2) communications and can run as TrustedInstaller, a built-in Windows system account with elevated permissions. MostereRAT can monitor foreground window activity associated with Qianniu - Alibaba's Seller Tool, facilitate RDP logins, and create hidden administrator accounts.

Timeline

  1. 08.09.2025 23:49 📰 2 articles

    MostereRAT Malware Campaign Targets Japanese Windows Users

    A new malware campaign, tracked as MostereRAT, has been identified targeting Japanese Windows users. The malware uses Easy Programming Language (EPL) to evade detection and disables antivirus (AV) and endpoint detection and response (EDR) tools. MostereRAT deploys legitimate remote access tools like AnyDesk, TigerVNC, and TightVNC for persistent control. The campaign begins with phishing emails containing malicious Word documents that download the malware. MostereRAT's capabilities include keylogging, data exfiltration, and the creation of hidden administrator accounts. The malware uses mutual TLS (mTLS) to secure command-and-control (C2) communications and can run as TrustedInstaller, a built-in Windows system account with elevated permissions. MostereRAT can monitor foreground window activity associated with Qianniu - Alibaba's Seller Tool, facilitate RDP logins, and create hidden administrator accounts. The malware uses Windows Filtering Platform (WFP) filters to block network traffic associated with a hard-coded list of security programs.

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