{
  "family": "tsklnk",
  "sample_count": 4,
  "category": "trojan",
  "description": "Trojan:Win32/Tsklnk (Task Link) is a specific classification for malware that abuses legitimate Windows Shortcut files (`.lnk`) and the Windows Task Scheduler to establish highly evasive persistence and execute malicious payloads. It is often a component of a larger infection chain, heavily utilized by fileless malware and USB-spreading worms to execute PowerShell or VBScript without leaving a traditional executable on the disk.<br><br><b>Understanding Tsklnk (Malicious LNKs)</b><br>To an end-user, Tsklnk often appears as a benign icon (like a folder or a PDF document) on a USB drive or the desktop. When double-clicked, the icon might briefly flash a command prompt before opening the expected document, masking the malicious activity. For a security analyst, Tsklnk represents an abuse of fundamental Windows OS features (Living off the Land). Because `.lnk` files and Scheduled Tasks are native, administrative tools, they often bypass traditional antivirus scans.<br><br><b>Execution and Persistence Mechanics</b><br>Tsklnk is frequently delivered via phishing (as an attached `.lnk` disguised as a document) (`T1566.002`) or via infected USB drives (`T1091`). The core of the threat lies in the 'Target' property of the Shortcut file. Instead of pointing to an application, the `.lnk` file executes `cmd.exe` or `powershell.exe` (`T1059.003`), passing it an obfuscated, base64-encoded command line (`T1027`). This command often reaches out to a C2 server to download and execute a secondary payload entirely in memory (`T1105`). To achieve persistence, the malware creates a hidden Scheduled Task (`T1053.005`) that points to a similarly malicious `.lnk` file or directly executes a PowerShell one-liner every time the user logs in.<br><br><b>Indicators of Compromise & Impact</b><br>The impact is a stealthy, persistent backdoor. Host-based IoCs include EDR alerts for `cmd.exe` or `powershell.exe` being spawned by `explorer.exe` (when the user clicks the shortcut) with exceptionally long, encoded command-line arguments. The presence of anomalous Scheduled Tasks executing scripts or binaries from temporary directories, and `.lnk` files on USB drives with targets pointing to `cmd.exe` rather than an application, are definitive IoCs.",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [],
  "enrichment_level": "expert-seo",
  "faq": [
    {
      "@type": "Question",
      "name": "What is Tsklnk and what threat category does it belong to?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Tsklnk 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 Tsklnk establish persistence and evade defensive controls?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Tsklnk 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 Tsklnk compromise?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Security teams responding to Tsklnk 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 Tsklnk?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Tsklnk 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 Tsklnk across enterprise endpoints?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Defenders should hunt for Tsklnk 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": [
    "T1204.002",
    "T1059.003",
    "T1053.005",
    "T1566.002"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-06-09",
  "mitre_attack_detail": [
    {
      "id": "T1566.002",
      "name": "Phishing: Spearphishing Link (Malicious .lnk attachments)",
      "tactic": "Initial Access"
    },
    {
      "id": "T1053.005",
      "name": "Scheduled Task/Job: Scheduled Task",
      "tactic": "Persistence"
    },
    {
      "id": "T1059.003",
      "name": "Command and Scripting Interpreter: Windows Command Shell",
      "tactic": "Execution"
    },
    {
      "id": "T1204.002",
      "name": "User Execution: Malicious File (Clicking the shortcut)",
      "tactic": "Execution"
    }
  ],
  "containment_steps": [
    "Audit the Windows Task Scheduler across the affected endpoints, looking for tasks with suspicious triggers (e.g., 'At Logon') and actions executing `powershell.exe` or `cmd.exe` with encoded arguments.",
    "Use EDR to hunt for process execution events where the command line contains strings like `-ExecutionPolicy Bypass`, `-WindowStyle Hidden`, or base64 encoding (`-enc`, `-EncodedCommand`).",
    "Disable Windows AutoRun/AutoPlay to prevent LNK files on USB drives from executing automatically.",
    "Delete the malicious `.lnk` files and the scheduled tasks they created."
  ],
  "what_to_avoid": [
    "Do not assume the system is clean just because an antivirus scan removed a dropped executable; Tsklnk often operates 'filelessly' via the registry and scheduled tasks.",
    "Avoid interacting with suspicious shortcut files manually on a live system; analyze the LNK file properties using specialized forensic tools (like LEC) in an isolated environment."
  ],
  "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"
  ]
}