Ransom.BAT.ZARLOCK.A

 Analysis by: Jemimah Mae Molina

 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

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 connects to certain websites to send and receive information.

It encrypts files with specific file extensions. It drops files as ransom note.

  TECHNICAL DETAILS

File Size:

3,404 bytes

File Type:

BAT

Memory Resident:

No

Initial Samples Received Date:

23 Jul 2019

Payload:

Connects to URLs/IPs, 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 adds the following processes:

  • chcp 866 → changes console code page to 866 (Russian)
  • %User Temp%\Rar.exe a -dw -hp{password} "{File Path}\{File Name}.{File Extension} .zarlock@{BLOCKED}l.cc" "{File Path}\{File Name}.{File Extension} "
  • %User Temp%\gpg.exe --import %User Temp%\brg.brg
  • %User Temp%\gpg.exe -r y1688 --yes -q --no-verbose --trust-model always -o %User Temp%\zarlock.KEY -e %User Temp%\rost.doc
  • wscript.exe %User Temp%\sh.vbs → contains command to delete shadow copies
  • %User Temp%\zarlock_Help_decrypt.html → contains ransom note

Other System Modifications

This Ransomware deletes the following files:

  • %User Temp%\brk.brk
  • %User Temp%\libassuan-0.dll
  • %User Temp%\libgpg-error-0.dll
  • %User Temp%\libgcrypt-20.dll
  • %User Temp%\libsqlite3-0.dll
  • %User Temp%\libnpth-0.dll
  • %User Temp%\zlib1.dll
  • %User Temp%\gpgconf.exe
  • %User Temp%\gpg.exe
  • %User Temp%\sh.vbs
  • %User Temp%\rtp.bat
  • %User Temp%\rar.exe
  • %User Temp%\brk.bat

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

Dropping Routine

This Ransomware drops the following files:

  • %User Temp%\rost.doc → contains password of compressed file
  • %User Temp%\Flag.txt → contains list of target files
  • %User Temp%\zarlock.KEY → encrypted rost.doc

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

Other Details

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

  • http://{BLOCKED}.{BLOCKED}.120.31/ok

Ransomware Routine

This Ransomware encrypts files with the following extensions:

  • .xls
  • .doc
  • .xlsx
  • .docx
  • .pdf
  • .rtf
  • .cdr
  • .psd
  • .dwg
  • .mdb
  • .dbf
  • .sqlite
  • .jpg
  • .jpeg
  • .backup
  • .rar
  • .zip
  • .sql
  • .sap
  • .GoBD

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

  • .zarlock@{BLOCKED}l.cc

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

  • %User Temp%\zarlock_Help_decrypt.txt
  • %User Temp%\zarlock_Help_decrypt.html

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.252.07

FIRST VSAPI PATTERN DATE:

23 Jul 2019

VSAPI OPR PATTERN File:

15.253.00

VSAPI OPR PATTERN Date:

24 Jul 2019

Step 1

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 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

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. DATA_GENERIC
  • Once located, select the file then press SHIFT+DELETE to delete it.
    *Note: Read the following Microsoft page if these steps do not work on Windows 7 and Windows Server 2008 (R2).
  • Step 4

    Scan your computer with your Trend Micro product to delete files detected as Ransom.BAT.ZARLOCK.A. 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 the following Trend Micro Support pages for more information:

    Step 5

    Restore encrypted files from backup.


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