Ransom.BAT.ZARLOCK.A

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.

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