TROJ_MALDROP.VYF

March 29, 2018
 Analysis by: Joselyn Canuela
 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.

  TECHNICAL DETAILS

File Size:

1,243,371 bytes

File Type:

PS1

Memory Resident:

Yes

Initial Samples Received Date:

26 Mar 2018

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 and executes the following files:

  • %Malware Path%\rundll.exe
  • %Malware Path%\svchost.exe

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\Software\Classes\
ms-settings\Shell\Open\
command

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Classes\
ms-settings\Shell\Open\
command
(Default) = "cmd /c start powershell.exe"

HKEY_CURRENT_USER\Software\Classes\
ms-settings\Shell\Open\
command
DelegateExecute = ""

Other Details

This Trojan adds the following scheduled tasks:

  • Task Name: my
    Schedule: every 1 minute
    Task to be run: %Malware Path%\rundll.exe
  • Task Name: Mytask
    Schedule: every log on
    Task to be run: %Malware Path%\rundll.exe

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.154.08

FIRST VSAPI PATTERN DATE:

27 Mar 2018

VSAPI OPR PATTERN File:

14.155.00

VSAPI OPR PATTERN Date:

28 Mar 2018

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

Restart in Safe Mode

[ Learn More ]

Step 3

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_CURRENT_USER\Software\Classes\ms-settings\Shell\Open
    • command

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.
  • %Malware Path%\rundll.exe
  • %Malware Path%\svchost.exe

Step 5

Deleting Scheduled Tasks

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

  • my - %Malware Path%\rundll.exe
  • Mytask - %Malware Path%\rundll.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

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_MALDROP.VYF. 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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