{
  "family": "sigrun",
  "sample_count": 3,
  "category": "ransomware",
  "description": "Ransom:Win32/Sigrun is a highly destructive Cryptographic Ransomware family designed to extort money from victims by rendering their data inaccessible. Like most modern ransomware, it relies on strong cryptographic algorithms to lock files, demanding payment in cryptocurrency in exchange for the decryption key.<br><br><b>Understanding Sigrun (Ransomware)</b><br>To an end-user, the impact is devastating: critical documents, databases, and media files are encrypted and appended with a specific extension, followed by the display of a ransom note on the desktop. For a security operations center (SOC), a Sigrun infection represents a critical incident requiring immediate containment to prevent the infection from spreading to network shares and crippling organizational infrastructure.<br><br><b>Execution and Encryption Mechanics</b><br>Sigrun is typically delivered via phishing emails containing malicious attachments (`T1566.001`), drive-by downloads, or by exploiting exposed Remote Desktop Protocol (RDP) services (`T1133`). Upon execution (`T1204.002`), it establishes persistence, often via the Registry Run keys or Scheduled Tasks (`T1547.001`). Crucially, before encrypting files, Sigrun executes commands (like `vssadmin.exe delete shadows` or `bcdedit /set {default} recoveryenabled No`) to inhibit system recovery (`T1490`). It then iterates through local drives and accessible network shares, utilizing strong encryption (e.g., AES + RSA) to lock files (`T1486`), leaving behind a ransom note (often a `.txt` or `.hta` file) detailing payment instructions.<br><br><b>Indicators of Compromise & Impact</b><br>The primary impact is severe data loss and business interruption. Host-based IoCs include rapid, massive file modification events detected by EDR, the execution of shadow copy deletion commands, the presence of the dropped ransom note, and modified file extensions. Network IoCs may include beaconing to the attacker's Command and Control (C2) server to register the infection and exchange cryptographic keys.",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [],
  "enrichment_level": "expert-seo",
  "faq": [
    {
      "@type": "Question",
      "name": "What is Sigrun and what threat category does it belong to?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Sigrun 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 Sigrun establish persistence and evade defensive controls?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Sigrun 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 Sigrun compromise?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Security teams responding to Sigrun 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 Sigrun employ during execution?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Sigrun 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 Sigrun, and what is the recommended recovery procedure?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Decryption availability for Sigrun 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": [
    "T1486",
    "T1204.002",
    "T1547.001",
    "T1490"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-06-09",
  "mitre_attack_detail": [
    {
      "id": "T1486",
      "name": "Data Encrypted for Impact",
      "tactic": "Impact"
    },
    {
      "id": "T1490",
      "name": "Inhibit System Recovery (Deleting volume shadow copies)",
      "tactic": "Impact"
    },
    {
      "id": "T1547.001",
      "name": "Boot or Logon Autostart Execution",
      "tactic": "Persistence"
    },
    {
      "id": "T1204.002",
      "name": "User Execution: Malicious File",
      "tactic": "Execution"
    }
  ],
  "containment_steps": [
    "IMMEDIATELY disconnect the infected machine from the network (unplug the Ethernet cable/disable Wi-Fi) to prevent the ransomware from traversing mapped network drives.",
    "Do not reboot the machine if encryption is actively occurring; capture a memory dump if possible to aid in potential cryptographic analysis.",
    "Identify the initial infection vector (e.g., the phishing email) and block it enterprise-wide.",
    "Restore systems from verified, offline backups that were completely inaccessible to the infected host."
  ],
  "what_to_avoid": [
    "Do not pay the ransom unless absolutely necessary for business continuity; payment funds criminal enterprises and guarantees nothing.",
    "Avoid relying solely on local backups or Volume Shadow Copies, as Sigrun explicitly targets and destroys these recovery mechanisms."
  ],
  "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,
  "target_platforms": [
    "Windows 11",
    "Windows 10",
    "Windows Server 2022",
    "Windows Server 2019"
  ]
}