{
  "family": "sivis",
  "sample_count": 7180,
  "category": "file_infector",
  "description": "Virus:Win32/Sivis is a destructive, polymorphic file infector that aggressively prepends its malicious code to executable files, causing widespread system corruption.<br><br><b>Understanding Sivis</b><br>To an end-user, Sivis causes applications to crash instantly upon opening and severely degrades system performance. For malware analysts, Sivis represents a classic, devastating viral threat. It is a parasitic virus; it does not just drop files onto the disk, it physically alters existing, legitimate executables (<code>.exe</code> files). Every time a user attempts to open an infected program, the virus executes first, spreading itself further before attempting to load the original application.<br><br><b>Execution and Evasion Strategies</b><br>Sivis typically infiltrates environments via infected USB drives, peer-to-peer file sharing, or as a secondary payload dropped by a trojan. Once active in memory, it scans the local hard drive and all mapped network shares for executable files. It utilizes polymorphism, altering its decryption loop and code structure with every infection, ensuring that no two infected files share the exact same cryptographic hash (MD5/SHA-256), thereby breaking traditional static AV signatures.<br><br><b>Indicators of Compromise & Impact</b><br>Incident responders should look for a sudden, massive wave of file modifications across the <code>%ProgramFiles%</code> directory. Anomalous spikes in CPU usage as the virus rapidly encrypts and prepends its code to files is a strong indicator. Due to its aggressive nature, Sivis often corrupts the PE (Portable Executable) headers of the files it infects, rendering them permanently unrecoverable. The impact is a total loss of application integrity across the host.",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [],
  "enrichment_level": "expert-seo",
  "faq": [],
  "faq_count": 0,
  "mitre_attack": [
    "T1055",
    "T1106",
    "T1091",
    "T1485",
    "T1140"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-06-09",
  "mitre_attack_detail": [
    {
      "id": "T1055",
      "name": "Process Injection",
      "tactic": "Defense Evasion"
    },
    {
      "id": "T1140",
      "name": "Deobfuscate/Decode Files or Information",
      "tactic": "Defense Evasion"
    },
    {
      "id": "T1485",
      "name": "Data Destruction",
      "tactic": "Impact"
    },
    {
      "id": "T1091",
      "name": "Replication Through Removable Media",
      "tactic": "Lateral Movement"
    },
    {
      "id": "T1106",
      "name": "Native API",
      "tactic": "Execution"
    }
  ],
  "containment_steps": [
    "Instantly sever the endpoint from the network; Sivis will aggressively hunt for and infect executables on shared corporate network drives.",
    "Assume all <code>.exe</code> and <code>.scr</code> files on the host are compromised and potentially corrupted beyond repair.",
    "Do not attempt to 'clean' the files using standard AV, as this frequently destroys the legitimate application data appended to the virus.",
    "Perform a complete bare-metal rebuild of the operating system and restore applications from known-clean, read-only installation media."
  ],
  "what_to_avoid": [
    "Avoid backing up executable files from the infected machine; you will only be backing up the polymorphic viral payloads.",
    "Do not execute any diagnostic tools directly from the infected host, as they will likely become infected upon execution."
  ],
  "target_industries": [
    "Global / Opportunistic"
  ],
  "motivation": "Opportunistic",
  "threat_actors": [
    "Unknown / Cybercriminal"
  ],
  "target_geographies": [
    "Global"
  ]
}