Analysis by: Mc Justine De Guzman
 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 executes commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information.

  TECHNICAL DETAILS

File Size: 182,784 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 07 Jan 2021
Payload: Drops files, Connects to URLs/IPs

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 adds the following folders:

  • %All Users Profile%\3101f8f780

(Note: %All Users Profile% is the common user's profile folder, which is usually C:\Documents and Settings\All Users on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit). )

It drops the following files:

  • %All Users Profile%\{SID of current user}

(Note: %All Users Profile% is the common user's profile folder, which is usually C:\Documents and Settings\All Users on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit). )

It drops and executes the following files:

  • %All Users Profile%\3101f8f780\gbudn.exe -> copy of itself

(Note: %All Users Profile% is the common user's profile folder, which is usually C:\Documents and Settings\All Users on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit). )

It adds the following processes:

  • "%System%\schtasks.exe" /Create /SC MINUTE /MO 1 /TN gbudn.exe /TR "%All Users Profile%\3101f8f780\gbudn.exe" /F

(Note: %All Users Profile% is the common user's profile folder, which is usually C:\Documents and Settings\All Users on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\ProgramData 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:

  • {SID of current user}

Backdoor Routine

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

  • Keylogging
  • Credential dumping
  • Remote command execution
  • Screen capture
  • Downloading a file

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

  • http://{BLOCKED}a.io
  • http://{BLOCKED}.{BLOCKED}.12.107
  • http://{BLOCKED}.{BLOCKED}.55.4

Download Routine

This Backdoor accesses the following websites to download files:

  • http://{BLOCKED}a.io/hfv23svj2/index.php
  • http://{BLOCKED}a.io/hfv23svj2/plugins/cred.dll
  • http://{BLOCKED}a.io/hfv23svj2/plugins/scr.dll
  • http://{BLOCKED}.{BLOCKED}.12.107/file{increasing number}.exe
  • http://{BLOCKED}.{BLOCKED}.55.4/cDILD8R6LQz2SaD5
  • http://{BLOCKED}.{BLOCKED}.55.4/configuration.php

It saves the files it downloads using the following names:

  • %All Users Profile%\3101f8f780\scr.dll -> used for screen capture
  • %All Users Profile%\3101f8f780\cred.dll -> used to get the credentials

(Note: %All Users Profile% is the common user's profile folder, which is usually C:\Documents and Settings\All Users on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit). )

Other Details

This Backdoor does the following:

  • It gets the credential of the following:
    • Mikrotik Winbox
    • Outlook
    • FileZilla
    • Pidgin
    • WCX FTP
    • RealVNC
    • TightVNC
    • TigerVNC
    • WinSCP
  • The stolen credentials includes the following (if applicable to the account):
    • username
    • password
    • email address
    • host
    • protocol
    • port number

It terminates itself if any of the following file(s) are present:

  • %All Users Profile%\Kaspersky Lab
  • %All Users Profile%\ESET
  • %All Users Profile%\Avira
  • %All Users Profile%\Panda Security
  • %All Users Profile%\AVG
  • %All Users Profile%\360TotalSecurity
  • %All Users Profile%\Bitdefender
  • %All Users Profile%\Norton
  • %All Users Profile%\Sophos
  • %All Users Profile%\Comodo
  • %All Users Profile%\AVAST Software
  • %All Users Profile%\Doctor Web

(Note: %All Users Profile% is the common user's profile folder, which is usually C:\Documents and Settings\All Users on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit). )

It adds the following scheduled tasks:

  • Task name: gbudn.exe
    • Action: %All Users Profile%\3101f8f780\gbudn.exe"

(Note: %All Users Profile% is the common user's profile folder, which is usually C:\Documents and Settings\All Users on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\ProgramData 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: 16.464.08
FIRST VSAPI PATTERN DATE: 08 Jan 2021
VSAPI OPR PATTERN File: 16.465.00
VSAPI OPR PATTERN Date: 09 Jan 2021

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.XXPE50FFF039

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

Deleting Scheduled Tasks

The following {Task Name} - {Task to be run} listed should be used in the steps identified below:

  • gbudn.exe - %All Users Profile%\3101f8f780\gbudn.exe

For Windows 2000, Windows XP, and Windows Server 2003:

  1. Open the Windows Scheduled Tasks. Click Start>Programs>Accessories>
    System Tools>Scheduled Tasks.
  2. Locate each {Task Name} values listed above in the Name column.
  3. Right-click on the said file(s) with the aforementioned value.
  4. Click on Properties. In the Run field, check for the listed {Task to be run}.
  5. If the strings match the list above, delete the task.

For Windows Vista, Windows 7, Windows Server 2008, Windows 8, Windows 8.1, and Windows Server 2012:

  1. Open the Windows Task Scheduler. To do this:
    • On Windows Vista, Windows 7, and Windows Server 2008, click Start, type taskschd.msc in the Search input field, then press Enter.
    • On Windows 8, Windows 8.1, and Windows Server 2012, right-click on the lower left corner of the screen, click Run, type taskschd.msc, then press Enter.
  2. In the left panel, click Task Scheduler Library.
  3. In the upper-middle panel, locate each {Task Name} values listed above in the Name column.
  4. In the lower-middle panel, click the Actions tab. In the Details column, check for the {Task to be run} string.
  5. If the said string is found, delete the task.

Step 6

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.
  • %All Users Profile%\3101f8f780\gbudn.exe
  • %All Users Profile%\3101f8f780\scr.dll
  • %All Users Profile%\3101f8f780\cred.dll

Step 7

Search and delete this folder

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %All Users Profile%\3101f8f780

Step 8

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


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