Analysis by: Bren Matthew Ebriega
ALIASES:

TrojanSpy:Win32/ElectroRAT!MSR (MICROSOFT); W32/Xegumumune.DVM!tr (FORTINET)

 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: 35114905 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 06 Jan 2021
Payload: Connects to URLs/IPs, Collects system information, Executes commands

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 Profile%\.mdworker.exe → Hidden

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

Autostart Technique

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

  • %User Startup%\mdworker.lnk

(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).)

Backdoor Routine

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

  • Execute Console Commands
  • Get Folder Content
  • Upload Folders
  • Upload/Download Files
  • Drop and Run Files
  • Get Process List
  • Terminate Processes
  • Take Screenshots
  • Start Keylogger

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

  • {BLOCKED}.{BLOCKED}.100.140

Information Theft

This Backdoor gathers the following data:

  • Machine ID
  • Username
  • Computer Name
  • OS Version
  • OS Name

Other Details

This Backdoor does the following:

  • It connects to the following url(s) to retrieve its C&C:
    • https://pastebin.com/raw/{BLOCKED}kd
    • https://pastebin.com/raw/{BLOCKED}C7
    • https://pastebin.com/raw/{BLOCKED}yv
    • https://pastebin.com/raw/{BLOCKED}rk

  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.XXPE50FFF042

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

Identify and terminate files detected as Backdoor.Win64.ELECTRORAT.YABA-A

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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.
  • %User Startup%\mdworker.lnk

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Backdoor.Win64.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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