{ "family": "msilbot", "sample_count": 1, "category": "ransomware", "description": "

Executive Summary

\nMSILBot (often detected as MSIL.Trojan or MSIL.Bot) refers to a broad category of botnet malware and remote access trojans (RATs) that are written and compiled using the Microsoft .NET framework (MSIL - Microsoft Intermediate Language). Because the .NET framework is deeply integrated into modern Windows operating systems, MSIL-based malware is highly prevalent, easy for attackers to develop rapidly, and capable of executing complex tasks without requiring additional runtime libraries.\n\n

Infection Vector and Technical Capabilities

\nMSILBots are distributed through various vectors, including malspam campaigns containing macro-enabled documents, malicious links in Discord or Telegram, and bundled with pirated software. They are often protected by readily available .NET obfuscators (like ConfuserEx) to evade static signature detection.\n\nUpon execution, MSIL-based bots exhibit versatile capabilities:\n\n\n

Threat Assessment

\nAn MSILBot infection is a severe security incident. It indicates that the infected endpoint has been compromised and incorporated into a larger botnet, granting remote attackers full administrative control over the machine. The versatility of .NET means the bot can quickly be repurposed from a simple DDoS node to a devastating info-stealer or ransomware loader.\n\n

Incident Response and Remediation

\n", "cta": "Published by the SystemHelpdesk team.", "aliases": [ "Trojan.MSIL", "MSIL.Bot", "Win32/MSIL.Agent" ], "enrichment_level": "expert-seo", "faq": [ { "@type": "Question", "name": "What is Msilbot and what threat category does it belong to?", "acceptedAnswer": { "@type": "Answer", "text": "Msilbot is classified as a Ransomware. Documented across security telemetry, it is engineered to execute unauthorized operations, establish persistent footholds on target endpoints, and facilitate malicious campaigns targeting enterprise and individual environments." } }, { "@type": "Question", "name": "How does Msilbot establish persistence and evade defensive controls?", "acceptedAnswer": { "@type": "Answer", "text": "Msilbot typically establishes persistence through registry run keys, scheduled tasks, or service installations, while evading signature-based antivirus solutions through code obfuscation, memory injection, or anti-analysis sandbox checks." } }, { "@type": "Question", "name": "What are the essential incident response steps for mitigating a Msilbot compromise?", "acceptedAnswer": { "@type": "Answer", "text": "Security teams responding to Msilbot should immediately isolate affected endpoints from the network, perform memory triage to capture volatile forensic artifacts, audit registry and startup persistence mechanisms, revoke exposed user credentials, and restore systems from verified, clean backups." } }, { "@type": "Question", "name": "What cryptographic algorithms and file targeting techniques does Trojan.MSIL employ during execution?", "acceptedAnswer": { "@type": "Answer", "text": "Trojan.MSIL typically leverages hybrid cryptographic architectures combining symmetric stream or block ciphers (such as AES-256 or ChaCha20) for rapid file encryption with asymmetric algorithms (such as RSA-2048 or Curve25519) to securely protect the session keys. It aggressively targets sensitive file extensions including corporate documents, databases, virtual disks, and backups while systematically executing commands to delete Volume Shadow Copies (vssadmin delete shadows /all /quiet) and disable system recovery options." } }, { "@type": "Question", "name": "Are decryptors available for Trojan.MSIL, and what is the recommended recovery procedure?", "acceptedAnswer": { "@type": "Answer", "text": "Decryption availability for Trojan.MSIL depends on whether security researchers or law enforcement (such as the No More Ransom initiative) have recovered the master private keys or discovered flaws in its key generation routines. Victims should never pay the extortion demand, as payment fuels criminal operations without guaranteeing file restoration. The recommended recovery procedure entails isolating infected hosts, conducting forensic disk imaging, identifying the root access vector, and restoring validated systems from immutable offline backups." } } ], "faq_count": 5, "mitre_attack": [ "T1059", "T1105", "T1071.001" ], "cisa_advisory": null, "last_updated": "2026-10-15", "type": "Botnet / Trojan (.NET)", "target_industries": [ "Healthcare", "Critical Infrastructure", "Enterprise" ], "motivation": "Financial Extortion", "threat_actors": [ "Unknown / Cybercriminal" ], "target_geographies": [ "Global" ], "attack_stage": [ "defense_evasion", "impact" ], "ecosystem": [ "windows_pe" ], "is_emerging": false, "mitre_attack_detail": [ { "id": "T1059", "name": "Command and Scripting Interpreter", "tactic": "Execution" }, { "id": "T1105", "name": "Ingress Tool Transfer", "tactic": "Command and Control" }, { "id": "T1071.001", "name": "Application Layer Protocol: Web Protocols (C2 Communication)", "tactic": "Command and Control" } ], "containment_steps": [ "Immediately isolate affected host(s) from the internal network (disconnect physical Ethernet and disable Wi-Fi/Bluetooth) to prevent Msilbot from spreading laterally or encrypting network-attached storage (NAS) and shared SMB volumes.", "Preserve volatile system memory (RAM capture) on a representative endpoint before attempting a reboot or power-down, as Msilbot symmetric encryption keys or uncompiled payload components may still reside in memory.", "Audit process execution logs and terminate active scripting interpreters (e.g. PowerShell, CMD, WScript) or commands executing 'vssadmin.exe delete shadows' or 'wbadmin' used by Msilbot to inhibit recovery.", "Investigate the initial compromise vector (such as exposed RDP instances, spearphishing attachments, or vulnerable edge gateways) and enforce an immediate credential reset for all compromised Active Directory accounts.", "Restore critical assets and databases exclusively from verified, air-gapped, or immutable offline backups once the Msilbot binary and related persistence hooks are eradicated." ], "what_to_avoid": [ "Do not restart or power cycle infected systems prematurely; doing so destroys volatile RAM encryption keys and may trigger bootloader locking logic embedded in Msilbot.", "Avoid negotiating or paying the extortion demand without prior forensic evaluation and consultation with incident response specialists, as payment does not guarantee data recovery.", "Do not connect clean backup drives or external storage to the affected network until Msilbot eradication is completely verified." ], "target_platforms": [ "Windows 11", "Windows 10", "Windows Server 2022", "Windows Server 2019" ] }