Backdoor.Win32.REVCODE.THDBABO


 PLATFORM:

Windows

 OVERALL RISK RATING:
 REPORTED INFECTION:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

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.

  TECHNICAL DETAILS

File Size:

12,255,744 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

21 Apr 2020

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:

  • %Application Data%\Downloads\Zoom.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 drops the following files:

  • %User Temp%\{random characters}.bat
  • %Application Data%\Downloads\Zoom.exe:ZoneIdentifier

(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).. %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 drops and executes the following files:

  • %User Temp%\ZoomInstaller.exe
    (Legitimate Zoom installer)

(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 adds the following processes:

  • %System%\notepad.exe "%Application Data%\Downloads\Zoom.exe"
  • %User Temp%\{random characters}.bat

(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 injects codes into the following process(es):

  • {malware fullpath}

Autostart Technique

This Backdoor drops the following file(s) in the Windows User Startup folder to enable its automatic execution at every system startup:

  • Zoom.vbs

Backdoor Routine

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

  • Add registry key
  • Add registry value
  • Change saved data on clipboard
  • Clear clipboard
  • Close all connections
  • Copy file
  • Delete file
  • Delete key-log
  • Delete registry key
  • Delete registry value
  • Download file
  • Edit registry value
  • Execute downloaded file
  • Execute file
  • Get all connections
  • Get application list
  • Get audio drivers list
  • Get devices state list
  • Get hardware information
  • Get installed devices
  • Get key-log information
  • Get process list
  • Get registry key list
  • Get registry value list
  • Get saved data on clipboard
  • Get service list
  • Get thumbnail
  • Get webcam drivers
  • Get webcam snapshot
  • Open cmd
  • Pause service
  • PDG proxy start
  • PDG proxy stop
  • PDG screen stream start
  • PDG screen stream stop
  • Remote code execution
  • Rename registry value
  • Resume process
  • Resume service
  • Screen stream start
  • Screen stream stop
  • Set process priority
  • SSL screen start
  • SSL screen stop
  • Start audio stream
  • Start keylog stream
  • Start service
  • Start Wireless Access Point
  • Stop audio stream
  • Stop keylog stream
  • Stop service
  • Stop Wireless Access Point
  • Suspend process
  • Terminate process
  • Uninstall application
  • Uninstall service
  • Upload file

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

  • dabm{BLOCKED}.wm{BLOCKED}.to

Stolen Information

This Backdoor sends the gathered information via HTTP POST to the following URL:

  • https://213.{BLOCKED}.{BLOCKED}.96/recv7.php

Other Details

This Backdoor does the following:

  • It terminates itself if the any of following processes is found:
    • aswidagent.exe
    • avastsvc.exe
    • avastui.exe
    • avgsvc.exe
    • avgui.exe
    • avp.exe
    • bdagent.exe
    • bdwtxag.exe
    • dwengine.exe
    • mpcmdrun.exe
    • msmpeng.exe
    • nissrv.exe
    • ollydbg.exe
    • procexp.exe
    • procexp64.exe
    • procmon.exe
    • procmon64.exe
    • windbg.exe
  • It terminates itself when executed in the following Virtual Environments:
    • Kernel-based Virtual Machine
    • Microsoft Hypervisor
    • Parallels Hypervisor
    • VirtualBox
    • VMware
    • Xen Virtual Machine Manager
  • It terminates itself if its file name is found similar to any of the following:
    • malware
    • sample
    • sandbox
  • It gathers the following information:
    • Battery Information
      • Estimated Charge Remaining
      • Estimated Runtime
    • Computer Information
      • Domain
      • Last Bootup
      • Name
      • Uptime
      • Username
    • Desktop Monitor Information
      • Screen Height
      • Screen Width
    • Memory Information
      • RAM Capacity
      • RAM Manufacturer
      • RAM Speed
    • Network Adapter Configuration
      • MAC Address
      • LAN IP
    • OS Information
      • Architecure
      • Build Number
      • Language
      • Version
    • Processor Information
      • Max Clock Speed
      • Processor Name
    • Video Controller Information
      • Driver Version
      • Name

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.826.03

FIRST VSAPI PATTERN DATE:

24 Apr 2020

VSAPI OPR PATTERN File:

15.827.00

VSAPI OPR PATTERN Date:

25 Apr 2020

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.XXPE50FFF034

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

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%\Downloads\Zoom.exe
  • %Application Data%\Downloads\Zoom.exe:ZoneIdentifier
  • %User Startup%\Zoom.vbs
  • %User Temp%\{random characters}.bat

Step 6

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