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Backdoor.MSIL.REVENGERAT.BB

March 01, 2024
 Analysis by: Francesca Villasanta
 ALIASES:

Backdoor:MSIL/Bladabindi (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, Dropped by other malware


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 may be dropped by other malware.

It executes commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information.

It gathers certain information on the affected computer. It logs a user's keystrokes to steal information.

  TECHNICAL DETAILS

File Size:

165,888 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

01 Mar 2024

Payload:

Collects system information, Connects to URLs/IPs, Drops files, Executes files, Logs keystrokes, Modifies system registry

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.

It may be dropped by the following malware:

Installation

This Backdoor adds the following processes:

  • %Application Data%\Microsoft\Windows\explorer.exe
  • netsh firewall add allowedprogram "%Application Data%\Microsoft\Windows\explorer.exe" "explorer.exe" ENABLE
  • "%System%\cmstp.exe" /au %User Temp%\{8 Random characters}.inf

(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).. %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 adds the following mutexes to ensure that only one of its copies runs at any one time:

  • Windows Explorer

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Windows Explorer = "%Application Data%\Microsoft\Windows\explorer.exe" .

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Windows Explorer = "%Application Data%\Microsoft\Windows\explorer.exe" .

Other System Modifications

This Backdoor adds the following registry entries:

HKEY_USERS\{GUID}
di = !

HKEY_CURRENT_USER\Environment
SEE_MASK_NOZONECHECKS = 1

It adds the following registry keys as part of its installation routine:

HKEY_CURRENT_USER\Software\Windows Explorer

Backdoor Routine

This Backdoor executes the following commands from a remote malicious user:

  • Registry manipulation
  • Download and execute additional malware
  • Capture screen
  • Uninstalls itself and additional malware downloaded
  • Send Keylogger logs

It connects to the following websites to send and receive information:

  • tcp://{BLOCKED}l.hackcrack.io:32544

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • tcp://{BLOCKED}l.hackcrack.io:32544

Dropping Routine

This Backdoor drops the following files:

  • %Application Data%\Microsoft\Windows\explorer.exe → Copy of itself, with HIDDEN attribute. Dropped only if execution path is not %Application Data%\Microsoft\Windows\explorer.exe
  • %Application Data%\Microsoft\Windows\version.exe → with HIDDEN attribute, detected as Trojan.MSIL.REVENGERAT.BC
  • %User Temp%\{8 Random Characters}.inf

Information Theft

This Backdoor gathers the following information on the affected computer:

  • Volume Serial Number
  • Computer name
  • Username
  • Executable last write date
  • OS Version and Architecture
  • Presence of a webcam
  • Active window title bar
  • Registry value names under a specific key

It logs a user's keystrokes to steal information.

Other Details

This Backdoor does the following:

  • It abuses the Microsoft Connection Manager Profile Installer (CMSTP.exe) supplied by a malicious INF file to execute a malicious file:
    • %Application Data%\Microsoft\Windows\version.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).)

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

19.190.02

FIRST VSAPI PATTERN DATE:

01 Mar 2024

VSAPI OPR PATTERN File:

19.191.00

VSAPI OPR PATTERN Date:

02 Mar 2024

Step 1

Trend Micro Predictive Machine Learning detects and blocks malware at the first sign of its existence, before it executes on your system. When enabled, your Trend Micro product detects this malware under the following machine learning name:

     TROJ.Win32.TRX.XXPE50FFF078 

Step 2

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 3

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 4

Restart in Safe Mode

[ Learn More ]

Step 5

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_USERS\{GUID}
    • di=!
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Windows Explorer="%Application Data%\Microsoft\Windows\explorer.exe" .
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Windows Explorer="%Application Data%\Microsoft\Windows\explorer.exe" .
  • In HKEY_CURRENT_USER\Environment
    • SEE_MASK_NOZONECHECKS=1

Step 6

Delete this registry key

[ 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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • HKEY_CURRENT_USER\Software\Windows Explorer

Step 7

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.  
  • %Application Data%\Microsoft\Windows\explorer.exe
  • %Application Data%\Microsoft\Windows\version.exe
  • %User Temp%\{8 Random Characters}.inf

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Backdoor.MSIL.REVENGERAT.BB. 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.


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