Trojan.LNK.Gen

Threat description

Details

CATEGORYMalware
TYPETrojan

Summary

Trojan.LNK.Gen is a Generic Detection for maliciously modified shortcut files (file extension .LNK) that are designed to trick users into mistakenly launching a malicious file.

Removal

Automatic action

Depending on the settings of your F-Secure security product, it will either automatically delete, quarantine or rename the suspect file, or ask you for a desired action.

More scanning & removal options

More information on the scanning and removal options available in your F-Secure product can be found in the Help Center.

You may also refer to the Knowledge Base on the F-Secure Community site for more information.

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Technical Details

LNK files are shortcut files that typically display an icon on the Desktop or in a folder, linked to a specified folder or file located elsewhere on the system. Shortcut files are commonly used to make finding certain files or system locations much more convenient for the user.

Attackers however can modify shortcut files, or drop specially crafted ones, that point to malicious files or components silently installed on the system. When the user clicks on the 'booby-trapped' shortcut, they unwittingly launch the malicious file.

Malicious LNK files will usually mimic legitimate ones, using the file icons for popular programs such as Notepad, Word, PDF, etc to trick the user into accepting the shortcuts as authentic. Malicious LNK files are often spread via infected removable drives; in such cases, the actual malicious files are hidden on the drive, while the LNK file is visible.

Depending on the specific malware, clicking the shortcut can result in various actions. Some malware show no obvious actions after the shortcut is clicked, but will silently run malicious components in the background. Other will open a legitimate program (for example Word or Notepad) to distract the user, while still silently launching other components in the background.

Some LNK malware will also open the command prompt (cmd.exe) and execute malicious scripts in the background, so that several different malicious routines can run at the same time. Examples of such scripts include:

  • c start crack.vbs & start explorer ASA & exit
  • c start ..\Skypee\AutoIt3.exe /AutoIt3ExecuteScript ..\Skypee\googleupdate.a3x explorer "%CD%" & exit
  • c start COOL.vbs & start document.doc & exit
Other

The Trojan.LNK.Gen Generic Detection can also be triggered by LNK components used by malware families, particularly those that are written in the AutoIT or VBS languages, such as:

This detection will also identify malware executed from a shell and in some cases, will identify malware that contain specific parameters or instructions.

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