Trojan:W32/DatCrypt

Threat description

Details

CATEGORYMalware
TYPETrojan

Summary

Trojan:W32/DatCrypt drops a DLL file that encrypts files with specific extensions on the system. The DLL then informs the user that the affected files should be decrypted with a certain "utility program", which it also attempts to download and install on the system.A malware that engages in this type of behavior is known as ransomware.



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.

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Technical Details

Execution

The DLL file is installed in the system32 folder with a random name. While active, the DLL searches the hard drive for files with the following extensions:

  • ppsm
  • ppsx
  • ppam
  • potm
  • potx
  • pptm
  • pptx
  • xlam
  • xlsb
  • xltm
  • xltx
  • xlsm
  • xlsx
  • dotm
  • dotx
  • docm
  • docx
  • ppt
  • xls
  • doc
  • pst
  • mdb
  • wma
  • mp3
  • png
  • jpeg
  • jpg
  • pdf

Many of these extensions are for Microsoft Office documents; the others are common media formats.Files found are encrypted. The program then displays a message when the user clicks the encrypted file, informing them the file is 'corrupted':

Download

The DLL will display a system notification message related to the supposed file corruption:

When clicked, the message initiates a download of a "utility program" for decrypting the affected files. The download is from

  • https://datahelpercorp.com/[...].exe

The downloaded utility program is detected as Rogue:W32/DatDoc.

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