Modified by: Jay Bradley Nebre
 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted:

  • 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 deletes itself after execution.

  TECHNICAL DETAILS

File Size: 417,792 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 29 Jul 2019
Payload: Displays message/message boxes, Modifies system registry, Encrypts files, Deletes self after execution

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%\Microsoft\Windows\ctfmon.exe

(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(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It adds the following processes:

  • "%System%\cmd.exe" /e:on /c md "%Application Data%\Microsoft\Windows" & copy "%User Temp%\{Malware Name}.exe" "%Application Data%\Microsoft\Windows\ctfmon.exe" & reg add "HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run" /V "Alternative User Input" /t REG_SZ /F /D "\"%Application Data%\Microsoft\Windows\ctfmon.exe\" *"
  • %Application Data%\Microsoft\Windows\ctfmon.exe *
  • %System%\cmd.exe /c for /l %x in (1,1,999) do ( ping -n 3 127.1 & del "%User Temp%\Ransom_Win32_BURAN_A_fa9fa1.exe" & if not exist "%User Temp%\Ransom_Win32_BURAN_A_fa9fa1.exe" exit )
  • reg add "HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run" /V "Alternative User Input" /t REG_SZ /F /D "\"%Application Data%\Microsoft\Windows\ctfmon.exe\" *"
  • "%System%\cmd.exe" /C bcdedit /set {default} bootstatuspolicy ignoreallfailures
  • "%System%\cmd.exe" /C bcdedit /set {default} recoveryenabled no
  • "%System%\cmd.exe" /C wbadmin delete catalog -quiet
  • "%System%\cmd.exe" /C wbadmin delete systemstatebackup
  • "%System%\cmd.exe" /C wbadmin delete systemstatebackup -keepversions:0
  • "%System%\cmd.exe" /C wbadmin delete backup
  • "%System%\cmd.exe" /C wmic shadowcopy delete
  • %System%\PING.EXE ping -n 3 127.1

(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).)

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

  • !!! YOUR FILES ARE ENCRYPTED !!!.TXT

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
Alternative User Input = "%Application Data%\Microsoft\Windows\ctfmon.exe *"

Other System Modifications

This Ransomware adds the following registry keys:

HKEY_CURRENT_USER\Software\Buran\
Service

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Buran\
Service
Public Key = "{random characters}"

HKEY_CURRENT_USER\Software\Buran\
Service
Machine ID = "{random characters}"

HKEY_CURRENT_USER\Software\Buran
Knock = "666"

Dropping Routine

This Ransomware drops the following files:

  • %User Temp%\{Random Characters}.buran
  • %User Temp%\{Random Characters}.buran

(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 deletes itself after execution.

Ransomware Routine

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

  • boot.ini
  • bootfont.bin
  • bootsect.bak
  • desktop.ini
  • ctfmon.exe
  • iconcache.db
  • master.exe
  • master.dat
  • ntdetect.com
  • ntldr
  • ntuser.dat
  • ntuser.dat.log
  • ntuser.ini
  • thumbs.db
  • !!! YOUR FILES ARE ENCRYPTED !!!.TXT
  • .cmd
  • .com
  • .cpl
  • .dll
  • .msc
  • .msp
  • .pif
  • .scr
  • .sys
  • .log
  • .lnk
  • .buran
  • .bat

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

  • $RECYCLE.BIN\
  • :\$Windows.~bt\
  • :\RECYCLER
  • :\System Volume Information\
  • :\Windows.old\
  • :\Windows\
  • :\intel\
  • :\nvidia\
  • :\inetpub\logs\
  • \All Users\
  • \AppData\
  • \Apple Computer\Safari\
  • \Application Data\
  • \Boot\
  • \Google\
  • \Google\Chrome\
  • \Mozilla Firefox\
  • \Mozilla\
  • \Opera Software\
  • \Opera\
  • \Tor Browser\
  • \Common Files\
  • \Internet Explorer\
  • \Windows Defender\
  • \Windows Mail\
  • \Windows Media Player\
  • \Windows Multimedia Platform\
  • \Windows NT\
  • \Windows Photo Viewer\
  • \Windows Portable Devices\
  • \WindowsPowerShell\
  • \Windows Photo Viewer\
  • \Windows Security\
  • \Embedded Lockdown Manager\
  • \Windows Journal\
  • \MSBuild\
  • \Reference Assemblies\
  • \Windows Sidebar\
  • \Windows Defender Advanced Threat Protection\
  • \Microsoft\
  • \Package Cache\
  • \Microsoft Help\

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

  • {8 digit characters}-{4 digit characters}-{4 digit characters}-{12 digit characters}

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 15.226.06
FIRST VSAPI PATTERN DATE: 10 Jul 2019
VSAPI OPR PATTERN File: 15.227.00
VSAPI OPR PATTERN Date: 11 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

Restart in Safe Mode

[ Learn More ]

Step 3

Identify and terminate files detected as Ransom.Win32.BURAN.A

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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
    • Alternative User Input = "%Application Data%\Microsoft\Windows\ctfmon.exe *"
  • In HKEY_CURRENT_USER\Software\Buran\Service
    • Public Key = "{random characters}"
  • In HKEY_CURRENT_USER\Software\Buran\Service
    • Machine ID = "{random characters}"
  • In HKEY_CURRENT_USER\Software\Buran
    • Knock = "666"

Step 5

Restore these modified registry values

[ Learn More ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\swprv
    • From: Type = "16"
      To: Type = ""10""

Step 6

Search and delete these components

[ Learn More ]
There may be some components 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.
  • %User Temp%\{Random Characters}.buran
  • %User Temp%\{Random Characters}.buran

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.Win32.BURAN.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 this Knowledge Base page for more information.

Step 8

Restore encrypted files from backup.


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