RANSOM_HIDDENTEARFENRIR.A

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 adds certain registry entries to disable the Task Manager. This action prevents users from terminating the malware process, which can usually be done via the Task Manager.

It connects to a website to send and receive information.

It encrypts files with specific file extensions. It encrypts files found in specific folders.

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.

Installation

This Ransomware drops the following files:

• %System%\BlackList.bin -> contains the files encrypted (encrypted afterwards)
• %User Temp%\wallpaper.bmp

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.. %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

Other System Modifications

This Ransomware also creates the following registry entry(ies) as part of its installation routine:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
EnableLUA = "0"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
PID = "{Hardware ID}"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
StartupRSW = "%User Startup%\Adobe Reader.exe"
could be deleted when your files are deleted

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Time Left = "{Time Left}"

It adds the following registry entries to disable the Task Manager:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableTaskMgr = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Group Policy Objects\
LocalUser\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableTaskMgr = "1"

It sets the system's desktop wallpaper to the following image:

Backdoor Routine

This Ransomware connects to the following websites to send and receive information:

• https://fenrir-ransomware.{BLOCKED}hostapp.com/log.php

Information Theft

This Ransomware accesses the following site to download its configuration file:

• http://i12.{BLOCKED}s.ru/storage/9/1/2/ransompng_6304118_26774912.png -> download wallpaper

Other Details

This Ransomware does the following:

• It deletes shadow copies by executing following command:
  vssadmin.exe Delete Shadows /Quiet /All
• Deletes Encrypted Files after 72 hours or when the reconfirmation for deletion is prompted.
• It displays a window that shows the following
  • the time left before all encrypted filed are deleted
  • a button that pretends to decrypt files when the password is inputted
  • a button that will delete all files after a confirmation message box
• 

Ransomware Routine

This Ransomware encrypts files with the following extensions:

• .mp4
• .avi
• .3gp
• .doc
• .docx
• .html
• .php
• .cpp
• .h
• .xml
• .xhtml
• .xls
• .xlsx
• .ppt
• .pptx
• .odt
• .csv
• .sql
• .mdb
• .asp
• .aspx
• .cs
• .sln
• .flv
• .wmv
• .wav
• .cer
• .p7b
• .pfx
• .psd
• .gif
• .rar
• .zip
• .7z
• .bek
• .bak
• .jpe
• .tex
• .bmp
• .ods
• .dbf
• .db
• .tif
• .1cd
• .tax
• .cry
• .vsd
• .pdf
• .gif
• .gbr
• .mdf
• .sdf
• .dwg
• .dxf
• .dgn
• .stl
• .gho
• .v2i
• .3ds
• .ma
• .acc
• .vpd
• .pas
• .asm
• .txt
• .jpg
• .png
• .mp3

It encrypts files found in the following folders:

• %User Profile%\Desktop
• %User Profile%\Videos
• %User Profile%\Music
• %User Profile%\Downloads
• %User Profile%\Pictures
• %User Profile%\Documents
• %User Profile%\Favorites
• All Drives

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

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

• program files
• windows

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

• .{First 10 characters of Hardware ID}