Analysis by: Raymart Christian Yambot


Ransom:Win32/Fog.D (MICROSOFT)




  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes


Infection Channel: Downloaded from the Internet, Dropped by other malware

This Ransomware arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It drops files as ransom note. It avoids encrypting files with the following file extensions.


File Size: 100,352 bytes
File Type: DLL
Memory Resident: No
Initial Samples Received Date: 10 Jun 2024
Payload: Disables AV, Drops files, Encrypts files, Terminates processes

Arrival Details

This Ransomware arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.


This Ransomware drops the following files:

  • {Malware File Path}/DbgLog.sys → logs the behavior of the sample upon execution

It adds the following processes:

  • vssadmin.exe delete shadows /all /quiet

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • 6zErjcpDAekftPiSbEUGHU4dtFwY5adQ

Process Termination

This Ransomware terminates the following services if found on the affected system:

  • Dhcp
  • Dnscache
  • *sql*

It terminates the following processes if found running in the affected system's memory:

  • notepad.exe
  • calc.exe
  • *sql*

Other Details

This Ransomware does the following:

  • It empties the recycle bin of the affected machine.
  • It requires to be executed with the key(ID) in order to proceed with its malicious routine:
    • 8mlafY

It accepts the following parameters:

  • -ID {key}
  • -TARGET {path to encrypt}

Ransomware Routine

This Ransomware avoids encrypting files with the following strings in their file path:

  • tmp
  • winnt
  • Application Data
  • AppData
  • temp
  • thumb
  • $Recycle.Bin
  • System Volume Information
  • Windows
  • Boot

It appends the following extension to the file name of the encrypted files:

  • {original filename}.{original extension}.flocked

It drops the following file(s) as ransom note:

  • {encrypted directory}\readme.txt

It avoids encrypting files with the following file extensions:

  • .exe
  • .dll
  • .lnk
  • .sys
  • .CONTI


Minimum Scan Engine: 9.800
VSAPI OPR PATTERN File: 19.401.00
VSAPI OPR PATTERN Date: 13 Jun 2024

Step 1

Trend Micro Predictive Machine Learning detects and blocks malware at the first sign of its existence, before it executes on your system. When enabled, your Trend Micro product detects this malware under the following machine learning name:

    •  Troj.Win32.TRX.XXPE50FFF081

Step 2

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 users must disable System Restore to allow full scanning of their computers.

Step 3

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 4

Search and delete these files

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • {Malware File Path}/DbgLog.sys
  • {encrypted directory}/readme.txt

Step 5

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.FOG.C. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check the following Trend Micro Support pages for more information:

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