{
  "family": "webdialer",
  "sample_count": 2,
  "category": "advanced_threat",
  "description": "Dialer:Win32/Webdialer is a historical classification for a type of malware prevalent during the era of dial-up internet access. Its primary objective was financial fraud. The malware would silently disconnect the user's modem from their standard Internet Service Provider (ISP) and re-dial a premium-rate telephone number (often international), resulting in massive, unexpected charges on the victim's phone bill (`T1499`).<br><br><b>Understanding Webdialer (Premium Rate Dialers)</b><br>To an end-user, the infection was often discovered only when the phone bill arrived. While modern broadband (cable, fiber) makes traditional modem dialers largely obsolete on PCs, the concept survives in mobile malware (apps that silently send premium SMS messages). For a historical security context, Webdialer represents one of the earliest forms of direct monetization by malware authors.<br><br><b>Execution and Fraud Mechanics</b><br>Webdialers were frequently distributed via deceptive websites (often adult content or 'free software' sites). Users would be prompted to download a special 'viewer' or 'access tool'. Once executed, the malware would alter the Windows Dial-Up Networking (DUN) settings. It would drop the current connection, mute the modem speaker (to hide the dialing sounds), and establish a new connection to a hardcoded premium-rate number. The attackers controlled these numbers and received a payout from the telecom provider for the connection time.<br><br><b>Indicators of Compromise & Impact</b><br>The impact was purely financial extortion via the telecom billing system. Host-based IoCs included the creation of new, unauthorized Dial-Up Networking connections in the Windows Control Panel, modifications to modem configuration strings (e.g., `ATM0` to mute the speaker), and unexpected executables establishing persistence via the Registry Run keys. Network IoCs were physical: the phone line being tied up dialing international numbers.",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [],
  "enrichment_level": "expert-seo",
  "faq": [
    {
      "@type": "Question",
      "name": "What is Webdialer and what threat category does it belong to?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Webdialer is classified as a Advanced Threat. 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 Webdialer establish persistence and evade defensive controls?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Webdialer 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 Webdialer compromise?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Security teams responding to Webdialer 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 lateral movement and credential access tactics does Webdialer leverage in enterprise intrusions?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Webdialer frequently utilizes privileged account harvesting techniques such as LSASS memory dumping, Kerberoasting, and token impersonation to escalate privileges. Once administrative credentials are acquired, it pivots across the victim network utilizing living-off-the-land binaries (LOLBins) such as WMI, PowerShell remoting, and PsExec, or abuses remote desktop protocols (RDP) to reach critical internal repositories and domain controllers."
      }
    },
    {
      "@type": "Question",
      "name": "How does Webdialer maintain covert communications and evade perimeter network monitoring?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Webdialer often relies on multi-stage command and control (C2) architectures utilizing encrypted protocols over standard web ports (HTTPS/443 or DNS tunneling) to blend in with legitimate enterprise network traffic. Many variants incorporate proxy networks, domain fronting, or cloud services (such as Microsoft Graph API, Google Drive, or Telegram) to masquerade C2 channels, bypassing traditional signature-based egress filtering."
      }
    }
  ],
  "faq_count": 5,
  "mitre_attack": [
    "T1547.001",
    "T1562.001",
    "T1499"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-06-09",
  "mitre_attack_detail": [
    {
      "id": "T1499",
      "name": "Endpoint Denial of Service (Hijacking the modem connection for financial gain)",
      "tactic": "Impact"
    },
    {
      "id": "T1562.001",
      "name": "Impair Defenses: Disable or Modify Tools (Muting the modem speaker to hide the dialing action)",
      "tactic": "Defense Evasion"
    },
    {
      "id": "T1547.001",
      "name": "Boot or Logon Autostart Execution: Registry Run Keys / Startup Folder",
      "tactic": "Persistence"
    }
  ],
  "containment_steps": [
    "For legacy systems still using dial-up, physically disconnect the phone line from the modem.",
    "Delete any unauthorized connections found in the Windows Network Connections or Dial-Up settings.",
    "Run a full anti-malware scan to remove the executable responsible for altering the dial-up settings.",
    "Contact the telecommunications provider to dispute the fraudulent charges and request a block on premium-rate and international dialing."
  ],
  "what_to_avoid": [
    "Do not assume the threat is completely obsolete; similar logic is highly prevalent in modern Android malware targeting premium SMS services.",
    "Avoid relying solely on software firewalls to block this, as the attack vectors through the physical telecom infrastructure, not standard IP routing."
  ],
  "target_industries": [
    "Global / Opportunistic"
  ],
  "motivation": "Opportunistic",
  "threat_actors": [
    "Unknown / Cybercriminal"
  ],
  "target_geographies": [
    "Global"
  ],
  "attack_stage": [
    "execution",
    "persistence"
  ],
  "ecosystem": [
    "windows_pe"
  ],
  "is_emerging": false,
  "target_platforms": [
    "Windows 11",
    "Windows 10",
    "Windows Server 2022",
    "Windows Server 2019"
  ]
}