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Backdoor.PDF.TONESHELL.B.enc

December 07, 2023
 Analysis by: Raymart Christian Yambot
 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • 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.

  TECHNICAL DETAILS

File Size:

2,103,808 bytes

Memory Resident:

No

Initial Samples Received Date:

01 Nov 2023

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.

Backdoor Routine

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

  • {BLOCKED}.{BLOCKED}.{BLOCKED}.233

Information Theft

This Backdoor gathers the following data:

  • Computer Name
  • Username
  • System Volume Information

Other Details

This Backdoor does the following:

  • It adds the following event to ensure that only one of its copies run at any one time:
    • utdfyt
  • The decrypted content of this file is SolidPDFCreator.dll → Dropped file of Trojan.Win32.TONEINS.A
    • SolidPDFCreator.dll → Detected as Backdoor.Win32.TONESHELL.B
  • It requires being loaded by SysSettings64.exe located in %All Users Profile%\Proxifier\IncrediBuild directory.
    • SysSettings64.exe (A renamed legitimate copy of Solid PDF Creator Software) → Dropped file of Trojan.Win32.TONEINS.A
  • It requires the existence of the following folder in the designated directory to proceed with its intended routine:
    • %All Users Profile%\Downloads directory

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

18.848.03

FIRST VSAPI PATTERN DATE:

29 Nov 2023

VSAPI OPR PATTERN File:

18.849.00

VSAPI OPR PATTERN Date:

30 Nov 2023

Step 1

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 2

Scan your computer with your Trend Micro product to delete files detected as Backdoor.PDF.TONESHELL.B.enc. 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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