Backdoor.Win32.CARBANAK.A

April 26, 2019
 Analysis by: Jemimah Mae Molina
 ALIASES:

Win32:Crypt-SHO [Trj] (AVAST); PWS:Win32/Sekur.A (MICROSOFT)

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet

This malware is part of the leaked source code of Carbanak, as reported by FireEye in April 2019.

This Backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It listens on ports. It executes commands from a remote malicious user, effectively compromising the affected system. It reads its configuration file that contains commands and data to be sent to a remote server.

It takes advantage of certain vulnerabilities.

  TECHNICAL DETAILS

File Size:

150,528 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

23 Apr 2019

Arrival Details

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

  • %User Startup%\{random characters}.exe

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows 2003(32-bit), XP and 2000(32-bit), or C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit), 10(64-bit).)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • {random characters}

It injects codes into the following process(es):

  • services.exe - if AVG Product is installed
  • iexplore.exe - if Trend Micro Product is installed
  • mstsc.exe - if Trend Micro Product is installed and iexplore.exe is not found
  • svchost.exe

Backdoor Routine

This Backdoor listens on the following port(s):

  • 443

It executes the following commands from a remote malicious user:

  • Execute commands specified in the configuration file
  • Set the loaded state of the bot
  • Run Ammyy plugin
  • Update bot
  • Use specified proxy settings
  • Create or deletes a user with rights for RDP
  • Delete specified service or file
  • Download and executes a file in memory
  • Retrieve user credentials using the mimikatz library
  • Take a screenshot and sends it to the C&C server
  • Run VNC plugin
  • Uninstall bot
  • List all running processes
  • Initiate a reverse shell to the server

It reads its configuration file that contains commands and data to be sent to a remote server.

Other Details

This Backdoor drops the following file(s)/component(s):

  • %All User Profile%\Application Data\Mozilla\{random characters}.bin

It does the following:

  • It can elevate its privilege via the following:
  • It accepts the following parameters:
    • -sd : launch itself with system rights
    • -ij : launch for injection into explorer
    • -u : update itself
  • It uses a named pipe to send and receive commands.

It takes advantage of the following vulnerabilities:

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.956.05

FIRST VSAPI PATTERN DATE:

23 Apr 2019

VSAPI OPR PATTERN File:

14.957.00

VSAPI OPR PATTERN Date:

24 Apr 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

Restart in Safe Mode

[ Learn More ]

Step 4

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.
  • %All User Profile%\Application Data\Mozilla\{random characters}.bin
  • %User Startup%\{random characters}.exe

Step 5

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Backdoor.Win32.CARBANAK.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.


Did this description help? Tell us how we did.