{
  "family": "luhn",
  "sample_count": 1,
  "category": "trojan",
  "description": "Trojan:Win32/Luhn is a highly specialized InfoStealer designed with a singular focus: the theft of credit card and payment data from Point-of-Sale (PoS) systems, hospitality networks, and e-commerce endpoints. The name derives from the malware's utilization of the 'Luhn algorithm' (Modulus 10), a mathematical formula used to rapidly validate credit card numbers (`T1005`).<br><br><b>Understanding Luhn (PoS/Credit Card Stealers)</b><br>To an end-user or cashier, the infection is entirely invisible; the PoS terminal functions normally. For a business, Luhn represents a catastrophic data breach leading to massive PCI-DSS compliance fines, reputational destruction, and financial liability as customer cards are cloned and abused.<br><br><b>Execution and Extraction Mechanics</b><br>Luhn is typically deployed after an attacker has breached a corporate network (often via exposed RDP) and pivoted to the isolated PoS VLAN. Upon execution, it establishes stealthy persistence (e.g., as a hidden Windows Service). Its primary mechanism is 'RAM Scraping' (`T1005`). It continuously scans the volatile memory (RAM) of running processes (like the PoS application itself) looking for Track 1 and Track 2 magnetic stripe data. Before exfiltrating the data, it runs the scraped numbers through the built-in Luhn algorithm to ensure they are valid credit cards, discarding junk data to keep its exfiltration footprint minimal (`T1041`).<br><br><b>Indicators of Compromise & Impact</b><br>The impact is the mass compromise of customer financial data. Host-based IoCs include EDR alerts for anomalous processes constantly calling `ReadProcessMemory` against legitimate PoS applications, and the creation of hidden, encrypted staging files in `%Temp%` containing the validated card data. Network IoCs include a 'beacon' or exfiltration burst over HTTP/HTTPS, DNS tunneling, or ICMP to a C2 server, occurring at regular intervals or at the end of the business day.",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [],
  "enrichment_level": "expert-seo",
  "faq": [
    {
      "@type": "Question",
      "name": "What is Luhn and what threat category does it belong to?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Luhn is classified as a Trojan. 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 Luhn establish persistence and evade defensive controls?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Luhn 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 Luhn compromise?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Security teams responding to Luhn 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 secondary payloads and staging behaviors are commonly associated with Luhn?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Luhn frequently operates as a loader or dropper designed to establish a foothold before downloading and executing secondary high-impact malware payloads. Depending on the threat actor's objectives, these dropped modules can range from ransomware and banking injects to modular infostealers and remote management backdoors."
      }
    },
    {
      "@type": "Question",
      "name": "How can security operations teams effectively detect and hunt for Luhn across enterprise endpoints?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Defenders should hunt for Luhn by deploying behavioral endpoint detection and response (EDR) rules that monitor suspicious process spawning (such as cmd.exe or powershell.exe spawned from office documents or temporary directories), anomalous outbound network connections from non-browser binaries, and unauthorized modifications to Windows Run keys and scheduled task registries."
      }
    }
  ],
  "faq_count": 5,
  "mitre_attack": [
    "T1005",
    "T1041",
    "T1543.003"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-06-09",
  "mitre_attack_detail": [
    {
      "id": "T1005",
      "name": "Data from Local System: RAM Scraping (Continuously scanning memory for credit card data)",
      "tactic": "Collection"
    },
    {
      "id": "T1041",
      "name": "Exfiltration Over C2 Channel (Sending the validated Track 1/2 data to the attacker)",
      "tactic": "Exfiltration"
    },
    {
      "id": "T1543.003",
      "name": "Create or Modify System Process: Windows Service (Establishing persistent, stealthy execution on the PoS terminal)",
      "tactic": "Persistence"
    }
  ],
  "containment_steps": [
    "Immediately isolate the affected PoS terminals from the internet and the broader corporate network.",
    "Do not reboot the PoS terminals until a full memory dump (RAM) has been captured, as the malware operates heavily in memory and may store unexfiltrated cards there.",
    "Engage a specialized Payment Card Industry (PCI) forensic investigator (PFI) to determine the scope of the cardholder data breach.",
    "Review network segmentation to determine how the attacker pivoted from the corporate network into the isolated PoS environment."
  ],
  "what_to_avoid": [
    "Do not attempt to 'clean' a compromised PoS terminal; it must be completely wiped and reimaged from a known-good, secure baseline.",
    "Avoid relying solely on traditional AV on PoS systems; application whitelisting (AppLocker) is required to prevent unauthorized memory scrapers from running."
  ],
  "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 7"
  ]
}