Ransom.Win32.WORLDGRASS.THFOABB

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 encrypts files with specific file extensions. It encrypts files found in specific folders. It drops files as ransom note.

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 copies of itself into the affected system:

• D:\notpad.exe
• {Removable Drive}\notpad.exe

It drops the following files:

• %User Startup%\Windows Anti-Malware Servise.url

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows 2003(32-bit), XP and 2000(32-bit), or C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit), 10(64-bit).)

It adds the following processes:

• vssadmin delete shadows /all /quiet
• wmic shadowcopy delete
• bcdedit /set {default} bootstatuspolicy ignoreallfailures
• bcdedit /set {default} recoveryenabled no
• wbadmin delete catalog -quiet

Other System Modifications

This Ransomware changes the desktop wallpaper by modifying the following registry entries:

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = %User Temp%\{9 random characters}.jpg

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

• %User Temp%\{9 random characters}.jpg
  

Ransomware Routine

This Ransomware encrypts files with the following extensions:

• .1cd
• .3ds
• .3fr
• .3g2
• .accda
• .accdc
• .accdw
• .adp
• .ai
• .ai3
• .ai4
• .ai5
• .ai6
• .ai7
• .ai8
• .arw
• .ascx
• .asm
• .asmx
• .avs
• .bin
• .cfm
• .dbx
• .dc3
• .dcm
• .dcr
• .dmg
• .dwt
• .epsp
• .exe
• .exr
• .f4v
• .geo
• .glx
• .iff
• .key
• .kwm
• .max
• .mda
• .mde
• .mdf
• .mdw
• .mht
• .mpv
• .msg
• .myi
• .nef
• .odc
• .odm
• .odp
• .oft
• .onetoc2
• .opt
• .orf
• .p12
• .p7b
• .pam
• .pfx
• .pict
• .pl
• .pls
• .pps
• .ppsm
• .ps
• .psb
• .r3d
• .rgbe
• .rss
• .safe
• .slk
• .srn
• .svgz
• .swift
• .tab
• .tar.gz
• .tif
• .vbs
• .vob
• .xlk
• .xlm
• .xlt
• .xltm

It encrypts files found in the following folders:

• The following specific folders in C drive:
  • %Desktop%
  • %User Profile%\Links
  • %User Profile%\Contacts
  • %User Profile%\Documents
  • %User Profile%\Downloads
  • %User Profile%\Pictures
  • %User Profile%\Music
  • %User Profile%\OneDrive
  • %User Profile%\Saved Games
  • %Favorites%
  • %User Profile%\Searches
  • %User Profile%\Videos
  • %Public%\Documents
  • %Public%\Pictures
  • %Public%\Music
  • %Public%\Videos
  • %Public%\Desktop
• In other available drives

(Note: %Public% is the folder that serves as a repository of files or folders common to all users, which is usually C:\Users\Public in Windows Vista, 7, and 8.)

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

• .34r7hGr455

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

• {Encrypted Folder}\Read ME (Decryptor).txt