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RANSOM_CYPEN.THEBBAH

June 08, 2018
 Analysis by: Hazel Ann Poligratis
 ALIASES:

Trojan:Win32/Occamy.C (Microsoft), Ransom.PGPSnippet (Malwarebytes), a variant of MSIL/Filecoder.LV (ESET-NOD32)

 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:

Downloaded from the Internet, Dropped by other malware


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 found in specific folders. It drops files as ransom note.

  TECHNICAL DETAILS

File Size:

1,351,680 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

22 May 2018

Payload:

Displays message/message boxes, Encrypts 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.

Installation

This Ransomware drops the following copies of itself into the affected system:

  • %Application Data%\KBFilt.exe

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming 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:

  • %Application Data%\host.txt - (contains the User Private Key)
  • %Application Data%\FrameworkLog\Logs.txt - (contains the list of drives and files)
  • %Application Data%\FrameworkLog\Associace.exe - (ransom note which does not run due to bugs)
  • %Application Data%\BouncyCastle.Crypto.dll - (collection of API used in Cryptography)

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming 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 creates the following folders:

  • %Application Data%\FrameworkLog

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming 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 adds the following mutexes to ensure that only one of its copies runs at any one time:

  • myProgramm

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Anti-Malware = %Application Data%\KBFilt.exe

File Infection

This Ransomware avoids infecting files that contain the following strings in their names:

  • {file name}.decodeme666@{BLOCKED}ta_com
  • !!!README_DECRYPT!!!.txt
  • hosts.txt
  • KBFilt.exe
  • BouncyCastle.Crypto.dll
  • Logs.txt

Ransomware Routine

This Ransomware encrypts files found in the following folders:

  • {All Available Drives}:\
  • {All Available Drives}:\{Folders and Sub-Folders}

It avoids encrypting files found in the following folders:

  • FrameworkLog

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

  • .decodeme666@{BLOCKED}ta_com

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

  • {Folders containing encrypted files}\!!!README_DECRYPT!!!.txt
  • %Application Data%\FrameworkLog\!!!README_DECRYPT!!!.txt

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

NOTES:

This ransomware displays the following:

It will also display the following message box to ensure that only one instance of itself is running.

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.266.04

FIRST VSAPI PATTERN DATE:

22 May 2018

VSAPI OPR PATTERN File:

14.267.00

VSAPI OPR PATTERN Date:

23 May 2018

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

Delete this 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\Software\Microsoft\Windows\CurrentVersion\Run
    • Anti-Malware = "%Application Data%\KBFilt.exe"

Step 5

Search and delete this folder

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
%Application Data%\FrameworkLog\

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.
  • %Application Data%\host.txt
  • %Application Data%\BouncyCastle.Crypto.dll
  • %Application Data%\KBFilt.exe

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_CYPEN.THEBBAH. 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 8

Restore encrypted files from backup.


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