{
  "family": "fleercivet",
  "sample_count": 2,
  "category": "advanced_threat",
  "description": "Adware:Win32/Fleercivet is a persistent adware family focused on click fraud and silent ad-injection. Unlike traditional adware that constantly bothers the user with visible pop-ups, Fleercivet is designed to operate more stealthily, generating revenue by simulating clicks on background advertisements or by quietly replacing legitimate ads on websites with those belonging to the attacker's affiliate network (`T1499`).<br><br><b>Understanding Fleercivet (Ad Injection)</b><br>To an end-user, the infection might manifest as slow browser performance or noticing that ads on familiar websites look strangely off-brand or lower quality. For a security team, Fleercivet is a network nuisance that indicates a failure in endpoint controls regarding Potentially Unwanted Programs (PUPs) and introduces the risk of malvertising.<br><br><b>Execution and Injection Mechanics</b><br>Fleercivet is distributed primarily via software bundling. Upon execution, it establishes persistence, often utilizing a Scheduled Task or modifying the `AppInit_DLLs` registry key (`T1546.010`) to ensure its DLL is loaded into every new process (specifically targeting browsers). Once hooked into the browser process (Chrome, Firefox, or Edge), Fleercivet uses Man-in-the-Browser (MitB) techniques to intercept web traffic. It parses the HTML of incoming web pages and dynamically injects its own JavaScript, which replaces existing ad banners or creates invisible iframes to click on ads silently in the background.<br><br><b>Indicators of Compromise & Impact</b><br>The impact is degraded system performance and exposure to untrusted advertising networks. Host-based IoCs include EDR alerts for DLL injection into browser processes (e.g., `chrome.exe`), unauthorized modifications to `AppInit_DLLs`, and unexpected Scheduled Tasks. Network IoCs include DNS requests and HTTP traffic directed towards known affiliate marketing and tracking domains that occur independently of user navigation.",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [],
  "enrichment_level": "expert-seo",
  "faq": [
    {
      "@type": "Question",
      "name": "What is Fleercivet and what threat category does it belong to?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Fleercivet 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 Fleercivet establish persistence and evade defensive controls?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Fleercivet 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 Fleercivet compromise?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Security teams responding to Fleercivet 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 Fleercivet leverage in enterprise intrusions?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Fleercivet 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 Fleercivet maintain covert communications and evade perimeter network monitoring?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Fleercivet 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": [
    "T1546.010",
    "T1499",
    "T1189"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-06-09",
  "mitre_attack_detail": [
    {
      "id": "T1499",
      "name": "Endpoint Denial of Service (Consuming resources via invisible ad loading and click fraud)",
      "tactic": "Impact"
    },
    {
      "id": "T1546.010",
      "name": "Event Triggered Execution: AppInit DLLs (Persistence and injection mechanism)",
      "tactic": "Persistence"
    },
    {
      "id": "T1189",
      "name": "Drive-by Compromise (Initial distribution via software bundles)",
      "tactic": "Initial Access"
    }
  ],
  "containment_steps": [
    "Use a robust anti-malware tool (like Malwarebytes or AdwCleaner) to locate and remove the Fleercivet DLLs and the associated injection registry keys.",
    "Verify and clean the `AppInit_DLLs` registry key (`HKLM\\SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Windows`).",
    "Reset all web browsers to default settings to ensure no malicious extensions were also dropped.",
    "Educate users on the risks of 'Express Installations' when downloading freeware."
  ],
  "what_to_avoid": [
    "Do not assume the browser is secure just because no new toolbars are visible; Fleercivet operates largely via injected code, not UI extensions.",
    "Avoid relying solely on traditional antivirus signatures, as the ad-injection scripts are frequently updated."
  ],
  "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"
  ]
}