TROJ_CRYPCTB.YWE

 Analysis by: Pearl Charlaine Espejo

 ALIASES:

Trojan-Ransom.Win32.Onion.dw (Kaspersky); Trojan.CTBLocker (Malwarebytes); Ransom-CTB!A9B023E2C8DF (McAfee); Ransom:Win32/Critroni.B (Microsoft); Trojan.Cryptolocker.E (Symantec)

 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware


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

It connects to certain websites to send and receive information.

  TECHNICAL DETAILS

File Size:

925,184 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

12 May 2015

Payload:

Drops files, Modifies files, Encrypts files

Arrival Details

This Trojan 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 Trojan drops the following copies of itself into the affected system and executes them:

  • %User Temp%\{random filename}.exe

(Note: %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.)

It drops the following files:

  • %ProgramData%\{randomly selected folder}\{random filename} (Windows Vista and above)
  • %All Users Profile%\Application Data\{randomly selected folder}\{random filename} (Windows XP and below)
  • %All Users Profile%\{random filename}.html (Windows Vista and above)
  • %ProgramData%\{random filename}.html (Windows Vista and above)
  • %All Users Profile%\Application Data\{random filename}.html (Windows XP and below)
  • %User Profile%\Documents\!Decrypt-All-Files-{random 7 characters}.bmp (Windows Vista and above)
  • %User Profile%\My Documents\!Decrypt-All-Files-{random 7 characters}.bmp (Windows XP and below)
  • %User Profile%\Documents\!Decrypt-All-Files-{random 7 characters}.txt (Windows Vista and above)
  • %User Profile%\My Documents\!Decrypt-All-Files-{random 7 characters}.txt (Windows XP and below)

(Note: %ProgramData% is the Program Data folder, where it usually is C:\Program Files in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData in 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.. %All Users Profile% is the All Users folder, where it usually is C:\Documents and Settings\All Users on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData 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.. %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 injects codes into the following process(es):

  • svchost.exe

Autostart Technique

This Trojan drops the following files:

  • %System%\Tasks\{random filename} (Windows Vista and above)
  • %Windows%\Tasks\{random filename}.job (Windows XP and below)

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.. %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

Other System Modifications

This Trojan modifies the following registry entries:

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = %User Profile%\{My Documents or Documents}\!Decrypt-All-Files-{random 7 characters}.bmp

(Note: The default value data of the said registry entry is {User Defined}.)

HKEY_CURRENT_USER\Control Panel\Desktop
TileWallpaper = "0"

(Note: The default value data of the said registry entry is "User Defined".)

HKEY_CURRENT_USER\Control Panel\Desktop
WallpaperStyle = "0"

(Note: The default value data of the said registry entry is "User Defined".)

Other Details

This Trojan connects to the following URL(s) to get the affected system's IP address:

  • http://ip.telize.com

It connects to the following website to send and receive information:

  • http://{BLOCKED}4qk625n6.onion.lt
  • http://{BLOCKED}4qk625n6.onion.gq
  • http://{BLOCKED}4qk625n6.tor2web.fi
  • http://{BLOCKED}4qk625n6.tor2web.org
  • http://{BLOCKED}4qk625n6.tor2web.blutmagie.de
  • http://{BLOCKED}4qk625n6.onion.cab

It encrypts files with the following extensions:

  • 3fr
  • 7z
  • accdb
  • ai
  • arw
  • bas
  • bay
  • blend
  • cdr
  • cer
  • cpp
  • cr2
  • crt
  • c
  • crw
  • cs
  • db
  • dbf
  • dcr
  • dds
  • dd
  • der
  • dng
  • docm
  • docx
  • doc
  • dwg
  • dxf
  • dxg
  • eps
  • erf
  • groups
  • indd
  • jpe
  • jpeg
  • jpg
  • js
  • kdc
  • kwm
  • mdb
  • mdf
  • md
  • mef
  • mrw
  • nef
  • nrw
  • odb
  • odm
  • odp
  • ods
  • odt
  • orf
  • p12
  • p7b
  • p7c
  • pdd
  • pdf
  • pef
  • pem
  • pfx
  • php
  • pl
  • pptm
  • ppt
  • pptx
  • psd
  • pst
  • ptx
  • pwm
  • py
  • r3d
  • raf
  • rar
  • raw
  • rtf
  • rw2
  • rwl
  • safe
  • sql
  • srf
  • srw
  • txt
  • vsd
  • wb2
  • wpd
  • wps
  • xlk
  • xlsm
  • xls
  • xlsb
  • xlsx
  • zip

It renames encrypted files using the following names:

  • {original file name and extension}.{random 7 characters}

NOTES:

This Trojan drops the following to all folders where files are encrypted:

  • !Decrypt-All-Files-{random 7 characters}.txt
  • !Decrypt-All-Files-{random 7 characters}.bmp

The dropped !Decrypt-All-Files-{random 7 letters}.tx contains the following ransom message:

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

It displays the following ransom message: The ransom message can be viewed in 7 different languages: French, Spanish, Austrian, German, Dutch, Italian and English

It allows the user to decrypt up to five files for free:

It asks the user to pay via Bitcoin payment:

If the connection is not established, it will instruct the user on how to pay the ransom in another computer with an internet connection.

It deletes copies of itself and its scheduled task after the time expired.

  SOLUTION

Minimum Scan Engine:

9.750

FIRST VSAPI PATTERN FILE:

11.640.06

FIRST VSAPI PATTERN DATE:

30 Apr 2015

VSAPI OPR PATTERN File:

11.641.00

VSAPI OPR PATTERN Date:

01 May 2015

Step 1

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

Step 2

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 3

Restart in Safe Mode

[ Learn More ]

Step 4

Search and delete this file

[ 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.
  • %ProgramData%\{randomly selected folder}\{random filename}   (Windows Vista and above)
  • %All Users Profile%\Application Data\{randomly selected folder}\{random filename}   (Windows XP and below)
  • %All Users Profile%\{random filename}.html   (Windows Vista and above)
  • %ProgramData%\{random filename}.html   (Windows Vista and above)
  • %All Users Profile%\Application Data\{random filename}.html   (Windows XP and below)
  • %System%\Tasks\{random filename}   (Windows Vista and above)
  • %WINDOWS%\Tasks\{random filename}.job   (Windows XP and below)
  • !Decrypt-All-Files-{random 7 characters}.bmp
  • !Decrypt-All-Files-{random 7 characters}.txt

Step 5

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_CRYPCTB.YWE. 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 this Knowledge Base page for more information.

Step 6

Reset your Desktop properties

[ Learn More ]

NOTES:

Restore the encrypted files by this malware from backup. Note that the encrypted files have the extension .{random 7 letters}.


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