Analysis by: Melvin Jhun Palbusa
 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet, Dropped by other malware

This Trojan 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: 1,906,688 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 01 Mar 2024
Payload: Drops files

Arrival Details

This Trojan 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 Trojan drops the following files:

  • %System%\zar32.dll → Detected as Backdoor.Win32.ZARDOOR.A
  • %System%\zor32.dll → Detected as Trojan.Win32.ZARDOOR.B
  • %User Profile%\zar32.dll
  • %User Profile%\zor32.dll
  • %User Temp%\zar32.dll
  • %User Temp%\zor32.dll

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.. %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).. %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It adds the following processes:

  • rundll32.exe {%System%/%User Profile%/%User Temp%}\zar32.dll MainEntry
  • rundll32.exe {%System%/%User Profile%/%User Temp%}\zor32.dll MainEntry

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

Other Details

This Trojan does the following:

  • It checks if the following strings are present in its memory:
    • 1ISSYSTEM
    • 1ISAUTURUN
      • If 1ISSYSTEM is present, it drops the following files to:
        • %System%\zar32.dll
        • %System%\zor32.dll
      • If 1ISSYSTEM is not present but 1ISAUTURUN present, it drops the following files to:
        • %User Profile%\zar32.dll
        • %User Profile%\zor32.dll
      • If both strings are not found, it drops the following files to:
        • %User Temp%\zar32.dll
        • %User Temp%\zar32.dll

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

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 19.196.02
FIRST VSAPI PATTERN DATE: 04 Mar 2024
VSAPI OPR PATTERN File: 19.197.00
VSAPI OPR PATTERN Date: 05 Mar 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.XXPE50FFF078

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

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.  
  • %System%\zar32.dll
  • %System%\zor32.dll
  • %User Profile%\zar32.dll
  • %User Profile%\zor32.dll
  • %User Temp%\zar32.dll
  • %User Temp%\zor32.dll

Step 5

Scan your computer with your Trend Micro product to delete files detected as Trojan.Win32.ZARLOADR.B. 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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