Analysis by: Clive Fuentebella
ALIASES:

Backdoor:MSIL/AsyncRat.AD!MTB (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 executes commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information.

It terminates itself if it detects it is being run in a virtual environment.

  TECHNICAL DETAILS

File Size: 46,080 bytes
File Type: EXE
Memory Resident: Yes
Payload: Connects to URLs/IPs, 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 adds the following mutexes to ensure that only one of its copies runs at any one time:

  • AsyncMutex_6SI8OkPnk

Backdoor Routine

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

  • Ping test
  • Execute sent plugin

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

  • {BLOCKED}89.ddns.net:8989
  • {BLOCKED}88.ddns.net:8988

Information Theft

Upon execution of the affected application, it gathers the following information:

  • Active window title
  • Current file path of the malware
  • Current malware version running in the machine
  • Flag stating if the malware is run as admin
  • HWID generated from processor count, username, computer name, OS version, and total size of the system directory
  • Installed AV products
  • OS information
  • Time installed
  • Username

Other Details

This Backdoor terminates itself if it detects it is being run in a virtual environment.

It does the following:

  • It does not continue if the total size of the system directory is less than 61000000000 bytes.
  • It does not continue if the operating system is XP.

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 16.718.07
FIRST VSAPI PATTERN DATE: 14 May 2021
VSAPI OPR PATTERN File: 16.719.00
VSAPI OPR PATTERN Date: 15 May 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.XXPE50FFF044

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

Scan your computer with your Trend Micro product to delete files detected as Backdoor.MSIL.ASYNCRAT.O. 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 the following Trend Micro Support pages for more information:


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