RANSOM_CERBER.BG

 Analysis by: Martin Xavier Co

 ALIASES:

Ransom:Win32/Cerber (Microsoft); Ransom.Cerber (Symantec)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet


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 modifies the Internet Explorer Zone Settings.

It connects to certain websites to send and receive information.

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

  TECHNICAL DETAILS

File Size:

95,905,140 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

10 Aug 2017

Payload:

Encrypts files, Drops files

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.

Autostart Technique

This Ransomware drops the following shortcut pointing to its copy in the User Startup folder to enable its automatic execution at every system startup:

  • {malware name}.lnk

Other System Modifications

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

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%TEMP%\tmp{random}.bmp"

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

Web Browser Home Page and Search Page Modification

This Ransomware modifies the Internet Explorer Zone Settings.

Dropping Routine

This Ransomware drops the following files:

  • %Desktop%\_HOW_TO_DECRYPT_MY_FILES_{random characters}_.hta
  • %Desktop%\_HOW_TO_DECRYPT_MY_FILES_{random characters}_.txt
  • %TEMP%\{8 random characters}\{4 random characters}.tmp
  • %TEMP%\tmp{random}.bmp
  • {folder of encrypted files}\_HOW_TO_DECRYPT_MY_FILES_{random characters}_.hta

(Note: %Desktop% is the desktop folder, where it usually is C:\Documents and Settings\{user name}\Desktop in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\Desktop 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.)

Other Details

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

  • 15.42.13.0/27:6893
  • 44.66.140.0/27:6893
  • 87.98.176.0/22:6893

It executes the following command to disable/stop/delete Windows components:

  • %System%\netsh.exe advfirewall set allprofiles state on
  • %System%\netsh.exe advfirewall reset

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

Ransomware Routine

This Ransomware encrypts files with the following extensions:

  • .doc
  • .docx
  • .xls
  • .xlsx
  • .jpg
  • .jpeg
  • .pdf
  • .rar
  • .zip
  • .ppt
  • .pptx
  • .avi
  • .mpg
  • .mpeg
  • .wmv

It encrypts files found in the following folders:

  • \bitcoin\
  • \excel\
  • \microsoft sql server\
  • \microsoft\excel\
  • \microsoft\microsoft sql server\
  • \microsoft\office\
  • \microsoft\onenote\
  • \microsoft\outlook\
  • \microsoft\powerpoint\
  • \microsoft\word\
  • \office\
  • \onenote\
  • \outlook\
  • \powerpoint\
  • \steam\
  • \the bat!\
  • \thunderbird\
  • \word\

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

  • bootsect.bak
  • iconcache.db
  • ntuser.dat
  • thumbs.db

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

  • :\$getcurrent\
  • :\$recycle.bin\
  • :\$windows.~bt\
  • :\$windows.~ws\
  • :\boot\
  • :\documents and settings\all users\
  • :\documents and settings\default user\
  • :\documents and settings\localservice\
  • :\documents and settings\networkservice\
  • :\intel\
  • :\logs\
  • :\msocache\
  • :\perflogs\
  • :\program files (x86)\
  • :\program files\
  • :\programdata\
  • :\recovery\
  • :\recycled\
  • :\recycler\
  • :\system volume information\
  • :\system.sav\
  • :\temp\
  • :\windows.old\
  • :\windows10upgrade\
  • :\windows\
  • :\winnt\
  • \appdata\local\
  • \appdata\locallow\
  • \appdata\roaming\
  • \local settings\
  • \public\music\sample music\
  • \public\pictures\sample pictures\
  • \public\videos\sample videos\
  • \tor browser\

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

NOTES:
It avoids infecting system with the following OS language codes:

  • 1049 - Russian
  • 1058 - Ukrainian
  • 1059 - Belarusian
  • 1064 - Tajik (Cyrillic)
  • 1067 - Armenian
  • 1068 - Azeri (Latin)
  • 1079 - Georgian
  • 1087 - Kazakh
  • 1088 - Kyrgyz
  • 1090 - Turkmen
  • 1091 - Uzbek (Latin)
  • 1092 - Tatar
  • 2072 - Romanian (Moldova)
  • 2073 - Romanian (Romania)
  • 2092 - Azeri (Cyrillic)
  • 2115 - Uzbek (Cyrillic)

  •   SOLUTION

    Minimum Scan Engine:

    9.850

    FIRST VSAPI PATTERN FILE:

    13.586.05

    FIRST VSAPI PATTERN DATE:

    10 Aug 2017

    VSAPI OPR PATTERN File:

    13.587.00

    VSAPI OPR PATTERN Date:

    11 Aug 2017

    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

    Scan your computer with your Trend Micro product to delete files detected as RANSOM_CERBER.BG. 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 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.  
    • %Desktop%\_HOW_TO_DECRYPT_MY_FILES_{random characters}_.hta
    • %Desktop%\_HOW_TO_DECRYPT_MY_FILES_{random characters}_.txt
    • %TEMP%\{8 random characters}\{4 random characters}.tmp
    • %TEMP%\tmp{random}.bmp
    • {folder of encrypted files}\_HOW_TO_DECRYPT_MY_FILES_{random characters}_.hta

    Step 5

    Reset your Desktop properties

    [ Learn More ]

    Step 6

    Restore encrypted files from backup.


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