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Trojan.Win32.FUPORPLEX.AF

May 20, 2020
 Analysis by: Clive Fuentebella
 ALIASES:

Mal/VMProtBad-A (SOPHOS LITE)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW


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.

It executes then deletes itself afterward.

It requires being executed with a specific argument/parameter, an additional component, or in a specific environment in order to proceed with its intended routine.

  TECHNICAL DETAILS

File Size:

514,560 bytes

File Type:

DLL

Memory Resident:

Yes

Initial Samples Received Date:

15 May 2020

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 copies of itself into the affected system:

  • %System%\ms{Characters based on C:/ volume serial number}app.dll
  • %System Root%\AppPatch\Custom\S{Random characters}.tmp

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.. %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.)

It executes then deletes itself afterward.

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • Global\ExpServicA

Other System Modifications

This Trojan modifies the following registry entries:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\
Services\SENS
ImagePath = %System Root%\system32\svchost.exe -k NetworkSvcGroup

HKEY_LOCAL_MACHINE\System\CurrentControlSet\
Services\SENS
DisplayName = ms{Characters based on C:/ volume serial number}app.dll

HKEY_LOCAL_MACHINE\System\CurrentControlSet\
Services\SENS
Description = ms{Characters based on C:/ volume serial number}app.dll

HKEY_LOCAL_MACHINE\System\CurrentControlSet\
Services\SENS
Group = UIGroup

HKEY_LOCAL_MACHINE\System\CurrentControlSet\
Services\SENS\Parameters
ServiceDll = %System%\ms{Characters based on C:/ volume serial number}app.dll

Other Details

This Trojan does the following:

  • It executes its payload if the following strings are found in its filename:
    • ms
    • app
    • cscdll.dll
    • sens.dll
  • It checks whether its process name is the following:
    • Winlogon.exe
    • svchost.exe
  • It needs the following files to perform its routine:
    • %System Root%\AppPatch\Ke{Random characters}.xsl

(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.)

It requires being executed with a specific argument/parameter, an additional component, or in a specific environment in order to proceed with its intended routine.

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.878.03

FIRST VSAPI PATTERN DATE:

19 May 2020

VSAPI OPR PATTERN File:

15.879.00

VSAPI OPR PATTERN Date:

20 May 2020

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.XXPE50FFF035

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

Restore this modified registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\SENS
    • ImagePath = %SystemRoot%\system32\svchost.exe -k netsvcs -p
  • In HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\SENS
    • DisplayName = @%SystemRoot%\system32\Sens.dll,-200
  • In HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\SENS
    • Description = @%SystemRoot%\system32\Sens.dll,-201
  • In HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\SENS
    • Group = ProfSvc_Group
  • In HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\SENS\Parameters
    • ServiceDll = %SystemRoot%\System32\sens.dll

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.
  • %System%\ms{Characters based on C:/ volume serial number}app.dll
  • %System Root%\AppPatch\Custom\S{Random characters}.tmp

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Trojan.Win32.FUPORPLEX.AF. 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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