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Trojan.Win32.WUSUB.A

 Analysis by: John Anthony Banes

 ALIASES:

Trojan:Win32/Wusub.A (Microsoft)

 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:

Dropped by other malware, Downloaded from the Internet


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.

As of this writing, the said sites are inaccessible.

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size:

167,936 bytes

File Type:

Other

Memory Resident:

No

Initial Samples Received Date:

20 Feb 2019

Payload:

Deletes files, Terminates processes, Connects to URLs/IPs

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:

  • %ProgramData%\TMPUSER.DAT - deleted afterwards.

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This contains application data for all users. This is usually C:\ProgramData in Windows Vista, 7, and 8.)

It creates the following folders:

  • %ProgramData%\Microsofts Help

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This contains application data for all users. This is usually C:\ProgramData in Windows Vista, 7, and 8.)

It terminates itself if it finds the following processes in the affected system's memory:

  • QHSAFETRAY.EXE
  • QHWATCHDOG.EXE
  • CMDAGENT.EXE
  • CIS.EXE
  • V3LITE.EXE
  • SPIDERAGENT.EXE
  • DWENGINE.EXE
  • DWARKDAEMON.EXE
  • BULLGUARDTRAY.EXE
  • BDAGENT.EXE
  • BULLGUARD.EXE
  • BDSS.EXE
  • BULLGUARD.EXE
  • V3MAIN.EXE
  • V3SP.EXE
  • EGUI.EXE
  • EKRN.EXE

Other System Modifications

This Trojan deletes the following files:

  • %ProgramData%\AMMYY\wmihost.exe
  • %ProgramData%\AMMYY\settings3.bin
  • %ProgramData%\Foundation\wmites.exe
  • %ProgramData%\Foundation\settings3.bin
  • %ProgramData%\Foundation1\wmites.exe
  • %ProgramData%\Foundation1\settings3.bin
  • %ProgramData%\Microsoft\wsus.exe
  • %ProgramData%\Microsoft\settings3.bin
  • %ProgramData%\Microsofts Help\wsus.exe
  • %ProgramData%\Microsofts Help\settings3.bin

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This contains application data for all users. This is usually C:\ProgramData in Windows Vista, 7, and 8.)

It deletes the following folders:

  • %ProgramData%\Settings
  • %ProgramData%\Microsoft\Enc
  • %ProgramData%\AMMYY
  • %ProgramData%\Foundation
  • %ProgramData%\Foundation1

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This contains application data for all users. This is usually C:\ProgramData in Windows Vista, 7, and 8.)

Process Termination

This Trojan terminates the following processes if found running in the affected system's memory:

  • wsus.exe

Download Routine

This Trojan connects to the following website(s) to download and execute a malicious file:

  • http://{BLOCKED}.{BLOCKED}.209.169/dat1.omg

It saves the files it downloads using the following names:

  • %ProgramData%\Microsofts Help\template_{hex string}.DATAHASH, which is decrypted and saved as %ProgramData%\Microsofts Help\wsus.exe

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This contains application data for all users. This is usually C:\ProgramData in Windows Vista, 7, and 8.)

As of this writing, the said sites are inaccessible.

Other Details

This Trojan does the following:

  • The file %ProgramData%\TMPUSER.DAT contains the output of executed command "net user /domain".
    If the string "WORKGROUP" is present in the file, the malware is terminated.
  • It executes the following commands to stop and delete a service named "foundation":
    • net.exe stop foundation
    • sc delete foundation
  • If running as an administrator, this malware registers the downloaded file as a service to ensure its automatic execution at every system startup by executing the following commands:
    • sc create foundation binPath= "%ProgramData%\Microsofts Help\wsus.exe -service" type= own start= auto error= ignore
    • net.exe start foundation y
  • If running as a user, this malware adds the following registry entries and scheduled tasks to enable automatic execution of the downloaded file at every system startup:
    • Registry:
      HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
      MicrosoftsSOftWare = %Program Data%\Microsofts Help\wsus.exe
    • Task Name: Microsoft System Protect
      Schedule: At log on of user
      Task to run: %Program Data%\Microsofts Help\wsus.exe

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This contains application data for all users. This is usually C:\ProgramData in Windows Vista, 7, and 8.)

It deletes the initially executed copy of itself

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.826.06

FIRST VSAPI PATTERN DATE:

20 Feb 2019

VSAPI OPR PATTERN File:

14.827.00

VSAPI OPR PATTERN Date:

21 Feb 2019

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

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 3

Restart in Safe Mode

[ Learn More ]

Step 4

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • MicrosoftsSOftWare = %Program Data%\Microsofts Help\wsus.exe

Step 5

Deleting Scheduled Tasks

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

  • Task Name: Microsoft System Protect
  • Task to run: %Program Data%\Microsofts Help\wsus.exe

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 6

Disable this malware service

[ Learn More ]
  •  foundation

Step 7

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.  
  • %ProgramData%\Microsofts Help

Step 8

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.
  • %ProgramData%\TMPUSER.dat

Step 9

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