{
  "family": "idlecrawler",
  "sample_count": 1,
  "category": "advanced_threat",
  "description": "Adware/Bot:Win32/Idlecrawler is a sneaky class of malware designed to exploit system resources or display advertisements exclusively when the user is not actively interacting with the computer (`T1489`). Its primary goal is monetization, either through invisible ad impressions (click fraud) or by utilizing the CPU/GPU for cryptomining, while avoiding detection by the user.<br><br><b>Understanding Idlecrawler (Idle-Time Execution)</b><br>To an end-user, the computer might seem perfectly fine while they are working, but the fans may spin up and the system may become unresponsive if left alone for a few minutes. For a security team, Idlecrawler represents a sophisticated evasion technique; the malware actively monitors user input (mouse movement, keystrokes) to determine when it is safe to execute its heavy payload.<br><br><b>Execution and Evasion Mechanics</b><br>Idlecrawler is typically distributed via software bundles or malicious browser extensions. Upon execution, it establishes persistence via Scheduled Tasks or Registry Run keys. It relies heavily on Windows APIs (like `GetLastInputInfo`) to monitor system idle time (`T1489`). When the idle threshold is met (e.g., 5 minutes of inactivity), the malware spawns a hidden browser window (`T1564.001`) to perform click fraud, or launches a mining process (`T1496`). As soon as the user moves the mouse or presses a key, Idlecrawler immediately suspends or kills the resource-intensive process to remain undetected.<br><br><b>Indicators of Compromise & Impact</b><br>The impact includes degraded hardware lifespan, wasted electricity, and potential exposure to secondary malware via the hidden ad networks. Host-based IoCs include EDR alerts for rapid process creation/termination correlated with user inactivity, and the presence of hidden `chrome.exe` or `iexplore.exe` processes running as background tasks rather than interactive applications. Network IoCs include bursts of traffic to advertising networks or mining pools that only occur when the workstation is locked or idle.",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [],
  "enrichment_level": "expert-seo",
  "faq": [
    {
      "@type": "Question",
      "name": "What is Idlecrawler and what threat category does it belong to?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Idlecrawler 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 Idlecrawler establish persistence and evade defensive controls?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Idlecrawler 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 Idlecrawler compromise?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Security teams responding to Idlecrawler 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 Idlecrawler leverage in enterprise intrusions?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Idlecrawler 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 Idlecrawler maintain covert communications and evade perimeter network monitoring?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Idlecrawler 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": [
    "T1489",
    "T1564.001",
    "T1496"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-06-09",
  "mitre_attack_detail": [
    {
      "id": "T1489",
      "name": "Service Stop (In reverse, pausing operations to evade detection when the user returns)",
      "tactic": "Defense Evasion"
    },
    {
      "id": "T1564.001",
      "name": "Hide Artifacts: Hidden Window (Spawning invisible browsers for ad fraud)",
      "tactic": "Defense Evasion"
    },
    {
      "id": "T1496",
      "name": "Resource Hijacking (Using idle CPU cycles for unauthorized cryptomining)",
      "tactic": "Impact"
    }
  ],
  "containment_steps": [
    "Use a reputable anti-malware tool to locate and remove the Idlecrawler executable and its associated persistence mechanisms.",
    "Review the Task Scheduler for any tasks configured to trigger specifically on system 'Idle' states.",
    "Implement EDR policies to detect and alert on hidden browser instances or known mining binaries executing in the background.",
    "Ensure endpoints are configured to sleep or lock automatically after a short period of inactivity, which can disrupt some idle-based malware."
  ],
  "what_to_avoid": [
    "Do not rely solely on the Windows Task Manager to find the malware; it will likely hide itself as soon as you open the Task Manager to look for it.",
    "Avoid leaving endpoints logged in and unlocked indefinitely."
  ],
  "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"
  ]
}