Analysis by: Joshua Maigue

 ALIASES:

Backdoor:Win32/Rescoms (Microsoft); Win32:RemcosRAT-A [Trj] (Avast)

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Canal de infecção: 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.

  TECHNICAL DETAILS

Tipo de compactação: 94,208 bytes
Tipo de arquivo: EXE
Data de recebimento das amostras iniciais: 23 Nov 2020
Carga útil: Drops files, Connects to URLs/IPs, Steals information, Downloads files, Deletes files, Terminates processes, Logs keystrokes, Displays message/message boxes, Collects system information

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 files:

  • %Application Data%\odum\logs.dat ? contains the information stolen from the victim

(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 creates the following folders:

  • %Application Data%\odum

(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 mutexes to ensure that only one of its copies runs at any one time:

  • odum_oglqgonkvj

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
remcos = \remcos.exe

Other System Modifications

This Backdoor adds the following registry entries:

HKEY_Current_User\Software\odum_oglqgonkvj
EXEpath = {HEX DATA}

Backdoor Routine

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

  • Activate Keylogger
  • Capture Image
  • Copy and paste text to and from clipboard
  • Download Files
  • Ping an address
  • Send keyboard/mouse input
  • Open the command prompt
  • Open the event viewer
  • Execute shell commands
  • Execute files
  • Browse directories
  • Obtain file/directory attributes
  • Change victim's Wallpaper
  • Upload files
  • Rename files
  • Delete files
  • Delete Directories
  • Get screenshot
  • Terminate processes
  • Play/record audio
  • Copy and paste text to and from clipboard
  • Clear Browser login and cookies
  • Perform registry changes
  • Play alarm
  • Display a messagebox
  • Sends keyboard input
  • Sends mouse click
  • Retrieve logins and cookies from the following browsers:
    • Google Chrome
    • Mozilla Firefox
    • Internet Explorer

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

  • {BLOCKED}.{BLOCKED}.225.50:42025

Information Theft

This Backdoor gathers the following data:

  • Product Name
  • User Privilege (is admin or not)
  • Locale Info
  • Windows Version
  • System Type (x32, x64)
  • User keystrokes
  • Clipboard Data
  • User Activity (Idle time)
  • User Name
  • Computer Name

Other Details

This Backdoor adds the following registry keys:

HKEY_Current_User\Software\odum_oglqgonkvj

  SOLUTION

Mecanismo de varredura mínima: 9.800
Primeiro arquivo padrão VSAPI: 16.392.05
Data do lançamento do primeiro padrão VSAPI: 04 Dec 2020
VSAPI OPR Pattern Version: 16.393.00
VSAPI OPR Pattern veröffentlicht am: 05 Dec 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.XXPE50FFF038

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_Current_User\Software\odum_oglqgonkvj
    • EXEpath = {HEX DATA}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • remcos = \remcos.exe

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.

HKEY_Current_User\Software\odum_oglqgonkvj

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%\odum\logs.dat

Step 8

Search and delete these folders

[ 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. %Application Data%\odum

Step 9

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