{
  "family": "byfh",
  "sample_count": 593,
  "category": "trojan_generic",
  "description": "Adware:Win32/Byfh (often associated with broader generic trojan downloaders) is a family of malicious software designed to aggressively monetize infected endpoints through forced advertising and click fraud.<br><br><b>What is Byfh?</b><br>To the layman, Byfh makes web browsing virtually impossible by injecting unwanted banner ads, pop-ups, and in-text hyperlinks into legitimate websites. For threat hunters and SOC analysts, Byfh represents a significant compromise of browser integrity and endpoint performance. It operates by hooking into the browser's rendering engine and intercepting web traffic to replace legitimate ads with those belonging to the attacker's affiliate network.<br><br><b>Infection Vectors & Threat Hunting</b><br>Byfh is predominantly distributed through deceptive software installers (bundling) or malicious browser extensions hosted on third-party sites. Upon installation, Byfh establishes deep hooks into the operating system. It frequently modifies DNS settings or installs a local proxy server to ensure all HTTP/HTTPS traffic is routed through its inspection engine. Threat hunters should look for anomalous proxy configurations in the Windows Registry (<code>HKCU\\Software\\Microsoft\\Windows\\CurrentVersion\\Internet Settings</code>) and the presence of unauthorized, self-signed root certificates installed in the Windows Certificate Store.<br><br><b>Forensic Analysis & Impact</b><br>The primary impact of Byfh is a severe degradation of the endpoint's security boundary. Because it intercepts TLS/SSL traffic to inject ads (a Man-in-the-Middle attack), it inherently exposes the victim's sensitive data, including passwords and session tokens, to potential theft. EDR systems will often detect Byfh based on its aggressive modification of browser shortcuts and its persistent attempts to inject DLLs into <code>chrome.exe</code> or <code>firefox.exe</code>.",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [],
  "enrichment_level": "expert-seo",
  "faq": [],
  "faq_count": 0,
  "mitre_attack": [
    "T1556",
    "T1562.001",
    "T1189",
    "T1112",
    "T1185"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-06-09",
  "mitre_attack_detail": [
    {
      "id": "T1185",
      "name": "Browser Session Hijacking",
      "tactic": "Collection"
    },
    {
      "id": "T1556",
      "name": "Modify Authentication Process",
      "tactic": "Credential Access"
    },
    {
      "id": "T1112",
      "name": "Modify Registry",
      "tactic": "Defense Evasion"
    },
    {
      "id": "T1562.001",
      "name": "Impair Defenses: Disable or Modify Tools",
      "tactic": "Defense Evasion"
    },
    {
      "id": "T1189",
      "name": "Drive-by Compromise",
      "tactic": "Initial Access"
    }
  ],
  "containment_steps": [
    "Quarantine the endpoint to prevent the exfiltration of intercepted web traffic and credentials.",
    "Remove any unauthorized local proxy settings configured in the Windows Internet Options and flush the DNS cache.",
    "Audit the Windows Certificate Store and delete any rogue Root CAs installed by Byfh to facilitate its TLS interception.",
    "Reset all web browsers to their default configurations and thoroughly scan the system with a dedicated anti-adware utility."
  ],
  "what_to_avoid": [
    "Do not ignore Byfh as a 'low severity' adware threat; its MitM capabilities mean sensitive corporate credentials may have been compromised.",
    "Avoid entering passwords or accessing secure portals on the infected machine until a full forensic remediation is complete."
  ],
  "target_industries": [
    "Global / Opportunistic"
  ],
  "motivation": "Opportunistic",
  "threat_actors": [
    "Unknown / Cybercriminal"
  ],
  "target_geographies": [
    "Global"
  ]
}