{
  "family": "hosts",
  "sample_count": 267,
  "category": "trojan_generic",
  "description": "BrowserModifier:Win32/Hosts (or simply 'Hosts file hijacker') is a generic heuristic detection for malware or adware that maliciously modifies the Windows HOSTS file to redirect web traffic, block security updates, or facilitate phishing.<br><br><b>What is a HOSTS Hijack?</b><br>For general consumers, a modified HOSTS file results in bizarre browsing behavior: attempting to visit <code>google.com</code> might redirect to a fake search engine, or attempting to visit <code>microsoft.com</code> simply times out. For incident responders, HOSTS hijacking is a rudimentary but highly effective DNS override technique. The Windows OS checks the local HOSTS file (<code>C:\\Windows\\System32\\drivers\\etc\\hosts</code>) before querying external DNS servers. Malware exploits this to sinkhole security traffic or redirect banking URLs to attacker-controlled phishing infrastructure.<br><br><b>Infection Vectors & Threat Hunting</b><br>Malware variants (ranging from simple adware to severe banking trojans) require local Administrator privileges to modify the HOSTS file. Upon execution, the malware appends hundreds of entries to the file. Commonly, it maps AV update domains (like <code>liveupdate.symantec.com</code> or <code>update.microsoft.com</code>) to <code>127.0.0.1</code> (localhost), effectively blinding the endpoint's security software. Alternatively, it maps financial domains (<code>chase.com</code>) to malicious IP addresses. Threat hunters can trivially detect this by monitoring the integrity and size of the HOSTS file.<br><br><b>Forensic Analysis & Impact</b><br>The impact ranges from simple annoyance (adware redirection) to severe financial loss (banking phishing) and compromised security posture. Incident responders should immediately open the HOSTS file in Notepad and review the entries. EDR tools frequently trigger alerts when processes other than <code>svchost.exe</code> or authorized admin tools attempt to write to the <code>\\drivers\\etc\\</code> directory.",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [],
  "enrichment_level": "expert-seo",
  "faq": [],
  "faq_count": 0,
  "mitre_attack": [
    "T1566",
    "T1498",
    "T1562.001",
    "T1584",
    "T1112"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-06-09",
  "mitre_attack_detail": [
    {
      "id": "T1562.001",
      "name": "Impair Defenses: Disable or Modify Tools",
      "tactic": "Defense Evasion"
    },
    {
      "id": "T1112",
      "name": "Modify Registry",
      "tactic": "Defense Evasion"
    },
    {
      "id": "T1566",
      "name": "Phishing",
      "tactic": "Initial Access"
    },
    {
      "id": "T1584",
      "name": "Compromise Infrastructure",
      "tactic": "Resource Development"
    },
    {
      "id": "T1498",
      "name": "Network Denial of Service",
      "tactic": "Impact"
    }
  ],
  "containment_steps": [
    "Open the Windows HOSTS file (<code>C:\\Windows\\System32\\drivers\\etc\\hosts</code>) with administrative privileges and delete all unauthorized entries.",
    "Reset the HOSTS file to the Windows default (typically just comments and a localhost mapping).",
    "Investigate how the malware gained administrative privileges to modify the file in the first place; a larger infection is likely present.",
    "Run a full EDR sweep to identify the parent executable (often adware or a banking trojan) that orchestrated the modification."
  ],
  "what_to_avoid": [
    "Do not assume the endpoint is clean just by fixing the HOSTS file; the malware that modified it is almost certainly still active.",
    "Avoid deleting the HOSTS file entirely; while Windows can recreate it, it is best practice to restore it to the Microsoft default template."
  ],
  "target_industries": [
    "Global / Opportunistic"
  ],
  "motivation": "Opportunistic",
  "threat_actors": [
    "Unknown / Cybercriminal"
  ],
  "target_geographies": [
    "Global"
  ]
}