Analysis by: Neljorn Nathaniel Aguas
ALIASES:

Trojan:Win64/Malgent!MSR (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. However, as of this writing, the said sites are inaccessible.

It gathers certain information on the affected computer.

  TECHNICAL DETAILS

File Size: 129,024 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 17 Jul 2024
Payload: Connects to URLs/IPs, 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 a copy of itself in the following folders using different file names:

  • c:\programdata\packagemanager\packagemanager.exe

Backdoor Routine

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

  • 0x1 → Upload file (filename: "exit")
  • 0x2 → Download file (filename: "exit")
  • 0x3 → Reverse shell
  • 0x4 → Update socket optval
  • 0x5 → Kill process
  • 0x8 → Delete Task
  • 0x9 → Check if task exists
  • 0xA → Create scheduled task
  • 0x60 → Update sleep interval
  • 0x61 → Change socket optval
  • 0x62 → PingBack C2 with same message

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

  • {BLOCKED}.{BLOCKED}.{BLOCKED}.14:443 → after connecting, sleeps for 2 minutes before reconnecting. Repeats indefinitely.

However, as of this writing, the said sites are inaccessible.

Information Theft

This Backdoor gathers the following information on the affected computer:

  • Computer Name
  • Username

Other Details

This Backdoor does the following:

  • It uses the following fingerprint when connecting to the IP address:
    • {Computer Name}/{Username}

It adds the following scheduled tasks:

  • Location: {Root Directory}
    Name: PackageManager
    Trigger: Daily at {Scheduled Task Create Time} → After triggered, repeat every 00:43:00 for a duration of 1 day.
    Action: Start a program → c:\programdata\packagemanager\packagemanager.exe

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 19.472.02
FIRST VSAPI PATTERN DATE: 17 Jul 2024
VSAPI OPR PATTERN File: 19.473.00
VSAPI OPR PATTERN Date: 18 Jul 2024

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.XXPE50FFF082

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 while in Safe Mode

  1. Still in safe mode, the following {Task Name}-{Task to be run} listed should be used in the steps identified below:
    • {Task Name} → {Root Location}\PackageManager
    • {Task to be run} → c:\programdata\packagemanager\packagemanager.exe
  2. For Windows 7 and Server 2008 (R2) users, click Start>Computer.
    • For Windows 8, 8.1, 10, and Server 2012 users, right-click on the lower left corner of the screen, then click File Explorer.
  3. In the Search Computer/This PC input box, type:
    • %System%\Tasks\{Task Name}
  4. Once located, select the file then press SHIFT+DELETE to delete it.
  5. Open Registry Editor. To do this:
    • For Windows 7 and Server 2008 (R2) users, click the Start button, type regedit in the Search input field, and press Enter.
    • For Windows 8, 8.1, 10, and Server 2012 (R2) users, right-click on the lower left corner of the screen, click Run, type regedit in the text box
  6. In the left panel of the Registry Editor window, double-click the following:
    • HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>Windows NT>CurrentVersion>Schedule>TaskCache>Tree>{Task Name}
  7. Locate the created entry and take note of the registry value's data:
    • ID={Task Data}
  8. After taking note of the data, delete the registry key:
    • HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>Windows NT>CurrentVersion>Schedule>TaskCache>Tree>{Task Name}
  9. In the left panel of the Registry Editor window, double-click the following:
    • HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>Windows NT>CurrentVersion>Schedule>TaskCache>Tasks
  10. Still in the left panel, locate and delete the registry key with the same name as the located Task Data in step #6:
    • ={Task Data}
  11. Close Registry Editor.

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.
  • c:\programdata\packagemanager\packagemanager.exe

Step 7

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