Tsklnk

Overview

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.

Understanding Tsklnk (Malicious LNKs)
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.

Execution and Persistence Mechanics
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.

Indicators of Compromise & Impact
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.

MITRE ATT&CK Techniques

Observed techniques used by this family, mapped to the MITRE ATT&CK framework:

Tactical Mitigations

Based on the techniques used by this family, consider the following defensive strategies:

• T1059.003: Restrict execution of Windows Command Shell (cmd.exe) and block unauthorized batch scripts.
• T1566.002: Inspect email links for known malicious domains and use link-rewriting services for time-of-click analysis.

Generated Detections (Boilerplate)

These YARA and Sigma rules are auto-generated based on the family name and aliases. They must be heavily tuned before deployment in a production environment.

YARA Rule

rule MALWARE_WIN_TSKLNK {
    meta:
        description = "Detects Tsklnk (trojan)"
        author = "SystemHelpdesk Boilerplate Generator"
        date = "2026-07-06"
    strings:
        $s1 = "tsklnk" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

Sigma Rule

title: Suspicious Tsklnk Activity
id: c467a59ca636f82bcab8caf527a15fb7
status: experimental
description: Detects generic indicators of the tsklnk malware family.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains:
            - "*tsklnk*"
    condition: selection
level: medium

Containment & Response Steps

Ordered checklist for responders. Adapt to your environment and engage professional support for active incidents.

1. 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.
2. Use EDR to hunt for process execution events where the command line contains strings like `-ExecutionPolicy Bypass`, `-WindowStyle Hidden`, or base64 encoding (`-enc`, `-EncodedCommand`).
3. Disable Windows AutoRun/AutoPlay to prevent LNK files on USB drives from executing automatically.
4. Delete the malicious `.lnk` files and the scheduled tasks they created.

What to Avoid

Common mistakes during response to this family that can destroy evidence, spread the infection, or worsen recovery.

1. 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.
2. 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.

References & External Analysis

• Search "tsklnk" on VirusTotal (External Analysis)

Frequently Asked Questions

Related Families (Category: trojan)

Explore other malware families in the same category:

• Tear
• Juicypotato
• Hooker
• Ramnif
• Cliptoshuffler

Machine-readable

Get this profile as JSON: https://jordanricky1604-ship-it.github.io/malware-families-catalog/api/tsklnk.json

Ecosystem & Interactive Environments

This profile is part of the Malware Families Catalog, a public dataset of 2,899 malware families. The catalog is also published across our ecosystem: Hugging Face, Kaggle, Zenodo, Replit, StackBlitz, CodeSandbox, and CodePen.