Analysis by: Arianne Grace Dela Cruz

ALIASES:

HEUR:Trojan-Dropper.Win32.Agent.gen (KASPERSKY); Trojan.GenericKD.35698631 (BITDEFENDER)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • 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: 270,336 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 28 Dec 2020
Payload: Modifies system registry, Adds scheduled tasks

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:

  • %User Profile%\test\7z.cab - contains Smanager_ssl.dll file detected as Backdoor.Win32.PHANTOMNET.YAAL-B
  • %Windows%\AppPatch\netapi32.dll - if executed with admin rights
  • %User Temp%\WMedia\{Random Numbers}.tmp - if executed without admin rights

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

  • "%System%\extrac32.exe" "%User Profile%\test\7z.cab" netapi32.dll /Y /L "%Windows%\apppatch\" - if executed with admin rights
  • "%System%\extrac32.exe" "%User Profile%\test\7z.cab" {Random Numbers}.tmp /Y /L "%User Temp%\WMedia" - if executed without admin rights
  • rundll32.exe "%User Temp%\WMedia\{Random Numbers}.tmp" Entery - if executed without admin rights

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

This Trojan adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
VVSup.Application
{Default} = VVSup.Application

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
VVSup.Application\CLSID
{Default} = {CLSID Value}

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{CLSID Value}
{Default} = VVSup.Application

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{CLSID Value}\ProgID
{Default} = VVSup.Application

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{CLSID Value}\InprocHandler32
{Default} = ole32.dll

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{CLSID Value}\LocalServer32
{Default} = {Malware Path}\{Malware File Name}.exe

It adds the following registry entries as part of its installation routine:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Svchost
{Service Name}Ex = {Service Name}

Other Details

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
VVSup.Application

It adds and runs the following services:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\{Service Name}
ImagePath = %System%\svchost.exe -k {Service Name}Ex

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\{Service Name}\Parameters
ServiceDll = %Windows%\apppatch\netapi32.dll

It does the following:

  • It would only install and execute the service if executed with admin rights. Otherwise, it will install the scheduled task.
  • The {Service Name} can be any of the following:
    • WlanSvr
    • GuiSvr
    • MediaSvr
    • Winrs
    • NvdiaSvr
    • Winmads
    • WaRpc
    • DisSvr
    • PlugSvr
    • Vsssvr
  • It will modify the extracted DLL and set the URLs that the DLL would connect to once executed.

It adds the following scheduled tasks:

  • If executed without admin rights:
    Task Name: Windows\Update
    Task to be run: "rundll32.exe "%User Temp%\WMedia\{Random Numbers}.tmp" Entery"

(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: 16.444.02
FIRST VSAPI PATTERN DATE: 29 Dec 2020
VSAPI OPR PATTERN File: 16.445.00
VSAPI OPR PATTERN Date: 30 Dec 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.XXPE50FFF039

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, and then delete this registry key

[ 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\{Service Name}
    • ImagePath = %System%\svchost.exe -k {Service Name}Ex
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\{Service Name}\Parameters
    • ServiceDll = %Windows%\apppatch\netapi32.dll

Step 5

Delete this registry key

[ Learn More ]

=Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator’s help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
    • VVSup.Application

Step 6

Delete this 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\SOFTWARE\Classes\VVSup.Application
    • {Default} = VVSup.Application
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\VVSup.Application\CLSID
    • {Default} = {CLSID Value}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{CLSID Value}
    • {Default} = VVSup.Application
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{CLSID Value}\ProgID
    • {Default} = VVSup.Application
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{CLSID Value}\InprocHandler32
    • {Default} = ole32.dll
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{CLSID Value}\LocalServer32
    • {Default} = {Malware Path}\{Malware File Name}.exe
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Svchost
    • {Service Name}Ex = {Service Name}

Step 7

Deleting Scheduled Tasks

The following {Task Name} - {Task to be run} listed should be used in the steps identified below:

Task Name: Windows\Update
Task to be run: "rundll32.exe "%User Temp%\WMedia\{Random Numbers}.tmp" Entery"

For Windows 2000, Windows XP, and Windows Server 2003:

  1. Open the Windows Scheduled Tasks. Click Start>Programs>Accessories>
    System Tools>Scheduled Tasks.
  2. Locate each {Task Name} values listed above in the Name column.
  3. Right-click on the said file(s) with the aforementioned value.
  4. Click on Properties. In the Run field, check for the listed {Task to be run}.
  5. If the strings match the list above, delete the task.

For Windows Vista, Windows 7, Windows Server 2008, Windows 8, Windows 8.1, and Windows Server 2012:

  1. Open the Windows Task Scheduler. To do this:
    • On Windows Vista, Windows 7, and Windows Server 2008, click Start, type taskschd.msc in the Search input field, then press Enter.
    • On Windows 8, Windows 8.1, and Windows Server 2012, right-click on the lower left corner of the screen, click Run, type taskschd.msc, then press Enter.
  2. In the left panel, click Task Scheduler Library.
  3. In the upper-middle panel, locate each {Task Name} values listed above in the Name column.
  4. In the lower-middle panel, click the Actions tab. In the Details column, check for the {Task to be run} string.
  5. If the said string is found, delete the task.

Step 8

Search and delete these files

[ 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.
  • %User Profile%\test\7z.cab
  • %Windows%\AppPatch\netapi32.dll
  • %User Temp%\WMedia\{Random Numbers}.tmp

Step 9

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Trojan.Win32.PHANTOMNET.YAAN-DRPR. 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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