{
  "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": [],
  "faq_count": 0,
  "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": [
    "Global / Opportunistic"
  ],
  "motivation": "Opportunistic",
  "threat_actors": [
    "Unknown / Cybercriminal"
  ],
  "target_geographies": [
    "Global"
  ]
}