A Primer on LNK Files: The Hidden Dangers of Windows Shortcuts
Malware operators have long relied on LNK files—commonly known as Windows shortcuts—as a covert and effective method for delivering trojans and executing malicious payloads. In this article, we’ll break down how LNK files work, explore their structure and vulnerabilities, and analyze attacker behavior based on a dataset of 30,000 recent malware samples.
What Are LNK Files?
LNK (shortcut) files in Windows provide a convenient way to launch applications, access folders, or open files without navigating to their full paths—like C:\Program Files\AppName\app.exe. Recognizable by the small arrow icon on the bottom-left corner, LNK files are deeply integrated into the Windows ecosystem.
Although they technically have the .lnk extension (visible in Command Prompt), File Explorer hides this extension by default. For example, Invoice.lnk will appear simply as Invoice, making it easier for attackers to disguise malicious files as harmless documents.
LNKs can link to more than just executables—they can open PDFs, images, scripts, or anything the system can associate with an application.
How LNK Files Are Created
Creating an LNK file is simple. Windows provides several ways:
- Right-click → Show more options → Create shortcut
- Copy a file → Paste shortcut
- Send to → Desktop (create shortcut)
- Right-click empty space → New → Shortcut
This simplicity is part of what makes them dangerous in the wrong hands.
Anatomy of a Malicious LNK File
LNK files use a binary format containing multiple fields. Key fields exploited by malware include:
| Field | Purpose |
|---|---|
| LINKTARGET_IDLIST | Points to the target file or folder |
| RELATIVE_PATH | Specifies the relative path to the target |
| COMMAND_LINE_ARGUMENTS | Passes additional arguments to the target, often used for exploitation |
Based on analysis of 30,000 malicious samples:
- 99.53% abuse
LINKTARGET_IDLIST - 75.49% manipulate
RELATIVE_PATH - 35.52% inject malicious code via
COMMAND_LINE_ARGUMENTS
Four Types of LNK-Based Malware Attacks
1. LNK Exploits
These are malformed LNK files designed to exploit Windows vulnerabilities—such as CVE-2010-2568, used in the infamous Stuxnet worm. Some samples also crash systems by abusing oversized ExtraBlock data structures.
2. Launching Malicious Files
These LNK files point to malware already present on disk, often masquerading as legitimate system files like desktop.ini.exe. They typically launch using trusted Windows tools such as wscript.exe.
3. Script Execution via Command-Line Arguments
Attackers embed payloads directly into the COMMAND_LINE_ARGUMENTS field, often targeting:
- PowerShell (
powershell.exe -enc [Base64Payload]) - CMD (
cmd.exe /c [command]) - Conhost (used to mask console execution)
- Forfiles (e.g.,
forfiles /p . /c [command])
4. Overlay Content Execution
Some LNKs append additional payloads after the official file ends. Techniques include:
- findstr or find to locate and execute hidden strings
- mshta.exe to run malicious HTA (HTML Application) code
- PowerShell tricks such as
Select-String,Get-Content, or.Substringto extract and run scripts
How to Spot a Malicious LNK File
🔍 Check Properties
Right-click the file → Properties → examine the Target. If it points to suspicious locations or contains unusual arguments, don’t click.
🧾 Look for Fake Icons
If a file appears to be a .txt or .pdf but is actually a .lnk, treat it with caution.
Monitor for Unusual Processes
If processes like cmd.exe, powershell.exe, or mshta.exe launch unexpectedly, investigate immediately.
Final Thoughts
LNK files are deceptively simple—but that’s exactly what makes them such an effective weapon for attackers. Their integration into Windows, combined with hidden extensions and flexible scripting capabilities, allow threat actors to bypass traditional detection mechanisms.
The best defense? Awareness.
Train users to inspect shortcuts, configure systems to show file extensions, and monitor command-line activity closely.
Don’t trust shortcuts—verify them.
