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HighSigmaHQSwachchhanda Shrawan Poudel (Nextron Systems)

Suspicious LNK Command-Line Padding with Whitespace Characters

Detects exploitation of LNK file command-line length discrepancy, where attackers hide malicious commands beyond the 260-character UI limit while the actual command-line argument field supports 4096 characters using…

Description

Detects exploitation of LNK file command-line length discrepancy, where attackers hide malicious commands beyond the 260-character UI limit while the actual command-line argument field supports 4096 characters using whitespace padding (e.g., 0x20, 0x09-0x0D). Adversaries insert non-printable whitespace characters (e.g., Line Feed \x0A, Carriage Return \x0D) to pad the visible section of the LNK file, pushing malicious commands past the UI-visible boundary. The hidden payload, executed at runtime but invisible in Windows Explorer properties, enables stealthy execution and evasion—commonly used for social engineering attacks. This rule flags suspicious use of such padding observed in real-world attacks.

Detection logic

Detection requirements

Platform
LinuxmacOSWindows

The rule states no platform. This is derived from the ATT&CK technique it maps to.

Log source product
windows
Log source category
process_creation

Known benign triggers

  • Unknown

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