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Threat Encyclopedia

TROJ_CRIBIT.B

ANALYSIS BY

Rhena Inocencio


ALIASES:

Backdoor.Win32.Androm.dowv (Kaspersky), Trojan.Fakeavlock (Symantec), Mal/VBInj-AO (Sophos), Win32/Filecoder.CE trojan (ESET)

PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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 threat, dubbed as BitCrypt, is a ransomware that steals funds from various cryptocurrency wallets.

To get a one-glance comprehensive view of the behavior of this Trojan, refer to the Threat Diagram shown below.

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 may be downloaded by other malware/grayware from remote sites.

It deletes the initially executed copy of itself.

TECHNICAL DETAILS

File Size:

312,032 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

09 Mar 2014

Payload:

Compromises system security, Terminates processes, 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.

It may be downloaded by the following malware/grayware from remote sites:

  • TSPY_FAREIT.BB

It may be downloaded from the following remote site(s):

  • http://{BLOCKED}directory.com/file/win.exe

Installation

This Trojan drops the following component file(s):

  • %Application Data%\BitCrypt.txt - contains ransom message
  • %Application Data%\BitCrypt.bmp - used as wallpaper
  • %Application Data%\bitcrypt.ccw - configuration file

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

It drops the following copies of itself into the affected system:

  • %Application Data%\{random filename}.exe - deleted after encryption routine

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

It leaves text files that serve as ransom notes containing the following:

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Bitcomint = "%Application Data%\{random filename}.exe" (This is deleted after the malware successfully encrypted user's files)

Other System Modifications

This Trojan deletes the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\SafeBoot\Minimal

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\SafeBoot\Network

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

Process Termination

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

  • taskmgr.exe
  • regedit.exe

Other Details

This Trojan encrypts files with the following extensions:

  • *.dbf
  • *.mdb
  • *.mde
  • *.xls
  • *.xlw
  • *.docx
  • *.doc
  • *.cer
  • *.key
  • *.rtf
  • *.xlsm
  • *.xlsx
  • *.txt
  • *.xlc
  • *.docm
  • *.xlk
  • *.text
  • *.ppt
  • *.djvu
  • *.pdf
  • *.lzo
  • *.djv
  • *.cdx
  • *.cdt
  • *.cdr
  • *.bpg
  • *.xfm
  • *.dfm
  • *.pas
  • *.dpk
  • *.dpr
  • *.frm
  • *.vbp
  • *.php
  • *.js
  • *.wri
  • *.css
  • *.asm
  • *.jpg
  • *.jpeg
  • *.dbx
  • *.dbt
  • *.odc
  • *.sql
  • *.abw
  • *.pab
  • *.vsd
  • *.xsf
  • *.xsn
  • *.pps
  • *.lzh
  • *.pgp
  • *.arj
  • *.gz
  • *.pst
  • *.xl

It deletes the initially executed copy of itself

NOTES:

This Trojan deletes itself, the copy that it drops and the added autorun registry after successfully encrypting user's files in all fixed drives.

It queries the value of the following key which contains the Microsoft Geographical Location Value:

HKEY_CURRENT_USER\Control Panel\International\Geo\Nation

The value is used as a part of the Bitcrypt ID.

It also executes the following commands:

  • cmd.exe /K bcdedit /set {bootmgr} displaybootmenu no
  • cmd.exe /K bcdedit /set {default} bootstatuspolicy ignoreallfailures

It appends the string bitcrypt2 to the encrypted file's extension.

SOLUTION

Minimum Scan Engine:

9.700

VSAPI OPR PATTERN File:

10.657.00

VSAPI OPR PATTERN Date:

10 Mar 2014

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

Remove the malware/grayware file that dropped/downloaded TROJ_CRIBIT.B

Step 3

Search and delete these files

[ Learn More ]
There may be some component 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.
 
  • %Application Data%\BitCrypt.txt
  • %Application Data%\BitCrypt.bmp
  • %Application Data%\bitcrypt.ccw

Step 4

Restoring Deleted Registry Keys

  1. Still in Registry Editor, in the left panel, double-click the following:
    HKEY_LOCAL_MACHINE>SYSTEM>CurrentControlSet>
    Control>SafeBoot>Minimal
  2. Right-click on the key and choose New>Key. Change the value of the new key to:
    {4D36E967-E325-11CE-BFC1-08002BE10318}
  3. Right-click on the value name and choose Modify. Change the value data of this entry to:
    DiskDrive
  4. In the left panel, double-click the following:
    HKEY_LOCAL_MACHINE>SYSTEM>CurrentControlSet>
    Control>SafeBoot>Network
  5. Right-click on the key and choose New>Key. Change the value of the new key to:
    {4D36E967-E325-11CE-BFC1-08002BE10318}
  6. Right-click on the value name and choose Modify. Change the value data of this entry to:
    DiskDrive
  7. Close Registry Editor.

Step 5

Scan your computer with your Trend Micro product to delete files detected as TROJ_CRIBIT.B. 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.


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