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Trojan.Win32.KILLFILES.SMTH

February 06, 2020
 Analysis by: Karen Ivy Titiwa
 ALIASES:

Trojan.Win32.Fsysna.fcp (KASPERSKY); Trojan:Win32/Musecador (MICROSOFT)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • 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.

  TECHNICAL DETAILS

Payload:

Deletes files

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 Temp%\{random}.TMP

(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).)

It drops and executes the following files:

  • %System Root%\123.bat → contains commands for adding registry entries

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

It adds the following processes:

  • cmd /c %System Root%\123.bat
      The bat file contains the following commands
    • reg add "hklm\software\microsoft\windows nt\currentversion\Image File Execution Options\ZhuDongFangYu.exe" /v debugger /t reg_sz /d "ntsd -d" /f
    • reg add "hklm\software\microsoft\windows nt\currentversion\Image File Execution Options\360tray.exe" /v debugger /t reg_sz /d "ntsd -d" /f
    • reg add "hklm\software\microsoft\windows nt\currentversion\Image File Execution Options\taskmgr.exe" /v debugger /t reg_sz /d "ntsd -d" /f
  • cmd.exe /c assoc .txt = exefile
  • cmd.exe /c ftype comfile={malware path}\{malware file name}.exe
  • cmd.exe /c ftype zipfile={malware path}\{malware file name}.exe
  • cmd.exe /c ftype jpgfile={malware path}\{malware file name}.exe
  • cmd.exe /c ftype txtfile={malware path}\{malware file name}.exe

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

Other System Modifications

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

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
jpgfile\Shell\Open\
Command
{default} = {malware directory}\{malware file name}.exe

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Image File Execution Options\
ZhuDongFangYu.exe
debugger = ntsd -d

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Image File Execution Options\
360tray.exe
debugger = ntsd -d

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Image File Execution Options\
taskmgr.exe
debugger = ntsd -d

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
zipfile\Shell\Open\
Command
{default} = {malware directory}\{malware file name}.exe

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
.txt
{default} = exefile

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
txtfile\shell\open\
command
{default} = {malware directory}\{malware file name}.exe

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
comfile\shell\open\
command
{default} = {malware directory}\{malware file name}.exe

Other Details

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
.txt

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
jpgfile

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
jpgfile\Shell

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
jpgfile\Shell\Open

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
jpgfile\Shell\Open\
Command

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
zipfile

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
zipfile\Shell

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
zipfile\Shell\Open

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
zipfile\Shell\Open\
Command

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Image File Execution Options\
ZhuDongFangYu.exe

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Image File Execution Options\
360tray.exe

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Image File Execution Options\
taskmgr.exe

It does the following:

  • It locates and deletes all executable files found in drive C.
  • Skips searching for executable files in hidden and system folders.
  • Replaced all deleted files with a modified copy of itself with the same file name as that of the deleted file.

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.612.06

FIRST VSAPI PATTERN DATE:

10 Jan 2020

VSAPI OPR PATTERN File:

15.613.00

VSAPI OPR PATTERN Date:

11 Jan 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:

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

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\SOFTWARE\Classes
    • .txt
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes
    • jpgfile
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes
    • zipfile
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options
    • ZhuDongFangYu.exe
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options
    • 360tray.exe
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options
    • taskmgr.exe

Step 5

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\.txt
    • {default} = exefile
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\comfile\shell\open\command
    • {default} = {malware directory}\{malware file name}.exe
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\txtfile\Shell\Open\Command
    • {default} = {malware directory}\{malware file name}.exe
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer
    • GlobalAssocChangedCounter = {data}

Step 6

Restore these modified registry values

[ 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\Microsoft\Windows\CurrentVersion\Explorer
    • GlobalAssocChangedCounter = from {data} to {data}

Step 7

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.
  • %User Temp%\{random}.TMP
  • %System Root%\123.bat

Step 8

Restore these deleted files from backup

*Note: Only Microsoft-related keys/values will be restored. If this malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.

Step 9

Scan your computer with your Trend Micro product to delete files detected as Trojan.Win32.KILLFILES.SMTH. 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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