Malware authors are implementing malicious link files into their campaigns more and more. This analysis video details how to quickly triage and analyze two different types of LNK-based threats.
Filename: Dossier.lnk
Video Walkthrough
How to Analyze a Malicious Windows LNK File
Malicious Microsoft Windows Shortcut (LNK) files are a favorite for initial access because they can be crafted to execute complex command-line arguments while appearing as harmless documents. Analyzing them requires a mix of static property inspection and deep-dive binary analysis.
Step 1: Safe Acquisition
The first rule of malware analysis is isolation. Always handle LNK files within a secure, air-gapped, or host-only virtual machine. Because LNK files can trigger execution just by the OS attempting to render their icon or via "right-click" context menus in some versions of Windows, handle them with extreme caution.
Step 2: Examine File Properties
Basic triage starts with the Windows Properties window. By right-clicking and selecting Properties, you can often see the "Target" field. Malware authors frequently use this field to hide PowerShell scripts, cmd.exe strings, or calls to mshta.exe. Look for unusually long paths or arguments that include -enc (encoded) or -WindowStyle Hidden.
Step 3: Hex Editor Analysis
Since the Windows UI often truncates long command strings in the "Target" field, a Hex Editor is essential. LNK files follow the Shell Link Binary File Format. By viewing the raw bytes, you can find the "String Data" section which may contain the full malicious command or secondary metadata like the original machine name or MAC address of the author’s computer.
Step 4: Decoding and De-obfuscation
Once you extract the command string, you'll likely encounter obfuscation. This often involves Base64 encoding, character replacement, or environment variable expansion (e.g., %TEMP%). Reverse engineering these scripts identifies the second-stage payload—whether it's a remote URL for a download or an embedded script hidden in the file's overlay data.
Conclusion
LNK files are effective because they abuse built-in Windows functionality. By combining property inspection with hex analysis, you can unmask the intent behind the shortcut and stop the infection chain before it reaches the payload stage. Always conduct your analysis in a controlled sandbox to keep your host system safe.