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TROJ_CRYPCTB.UKL

July 13, 2015
 Analysis by: Ryan Gardo
 Modified by: Francis Xavier Antazo
 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet


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:

749,242 bytes

File Type:

EXE

Initial Samples Received Date:

04 Jun 2015

Payload:

Connects to URLs/IPs, 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 files:

  • %Windows%\Tasks\{random filename2}.job
  • %User Profile%\My Documents\!Decrypt-All-Files-{random 7 characters 1}.txt
  • %User Profile%\My Documents\!Decrypt-All-Files-{random 7 characters 1}.bmp
  • %All Users Profile%\Application Data\{randomly selected path}\{random filename3} - for Windows XP and below.
  • %AppDataLocal%\{randomly selected path}\{random filename3} - for Windows 7 and above.

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.. %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.. %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.. %AppDataLocal% is the Application Data folder found in Local Settings, where it is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local 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 copies of itself into the affected system:

  • %User Temp%\{random filename1}.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 injects codes into the following process(es):

  • svchost.exe
  • explorer.exe

Autostart Technique

The scheduled task executes the malware every:

  • system startup

Other System Modifications

This Trojan modifies the following registry entries:

HKEY_CURRENT_USER\Control Panel\Desktop
TileWallpaper = "0"

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

HKEY_CURRENT_USER\Control Panel\Desktop
WallpaperStyle = "0"

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

HKEY_CURRENT_USER\Control Panel\Desktop
WallPaper = "%User Profile%\My Documents\!Decrypt-All-Files-{random 7 characters 1}.bmp"

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

Other Details

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

  • ip.telize.com

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

  • http://{BLOCKED}sp3sjyg.tor2web.fi
  • http://{BLOCKED}sp3sjyg.tor2web.blutmagie.de
  • http://{BLOCKED}sp3sjyg.onion.cab
  • http://{BLOCKED}sp3sjyg.onion.gq

It encrypts files with the following extensions:

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

NOTES:

This Trojan drops the following files when it is encrypts a file:

  • !Decrypt-All-Files-{random 7 characters 1}.txt
  • !Decrypt-All-Files-{random 7 characters 1}.bmp

The dropped Decrypt All Files {random characters}.txt contains the following ransom message:

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

It displays the ransom message in the following languages:

It decrypts five random files to entice the user that it is capable of recovering the files after payment of ransom:

It then asks the user to pay the ransom in bitcoin to automatically decrypt the files. It also contains instructions on how to buy bitcoins via cash, electronic currency, etc.:

It adds the file extension .{random 7 characters} to files it encrypts. It executes the following command to delete the volume's shadow copies, in order to hamper the restoration of the volume:

vssadmin delete shadows all

  SOLUTION

Minimum Scan Engine:

9.750

FIRST VSAPI PATTERN FILE:

11.706.08

FIRST VSAPI PATTERN DATE:

02 Jun 2015

VSAPI OPR PATTERN File:

11.707.00

VSAPI OPR PATTERN Date:

03 Jun 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

Restore this modified registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

 
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: TileWallpaper = "0"
      To: TileWallpaper = "{User Preference}"
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: WallpaperStyle = "0"
      To: WallpaperStyle = "{User Preference}"
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • From: WallPaper = "%User Profile%\My Documents\!Decrypt-All-Files-{random 7 characters}.bmp"
      To: WallPaper = "{User Preference}"

Step 5

To delete the added Scheduled Task:

For Windows 2000, Windows XP, and Windows Server 2003:

  1. Click on Start>Programs>Accessories>System Tools>Scheduled Tasks
  2. Double-click on a job file.
  3. Check if the malware path and file name is in the Run: box.
  4. If it does, delete the job file.
  5. Repeat step 2-4 for the remaining job files.

For Windows Vista, Windows 7, Windows Server 2008, Windows 8, Windows 8.1, and Windows Server 2012:

  1. Open the Windows Task Scheduler. To do this:
    • On Windows Vista, Windows 7, and Windows Server 2008, click Start, type taskschd.msc in the Search input field, then press Enter.
    • On Windows 8, Windows 8.1, and Windows Server 2012, right-click on the lower-left corner of the screen, click Run, type taskschd.msc, then press Enter.
  2. In the left panel, click Task Scheduler Library.
  3. In the upper-middle panel, select a Task.
  4. Check if the selected task starts the malware automatically. To do this, check the value in the Details column under the Actions tab in the lower-middle panel.
  5. If the malware path and file name is found, press DELETE and click Yes to delete the task.
  6. Repeat steps 3-5 for the remaining tasks.

Step 6

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.
  • !Decrypt-All-Files-{random 7 characters 1}.txt
  • !Decrypt-All-Files-{random 7 characters 1}.bmp

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_CRYPCTB.UKL. 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.

NOTES:

Restore the encrypted files from backup.


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