PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This Backdoor 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: 1,159,283 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 18 Apr 2020

Arrival Details

This Backdoor 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 Backdoor adds the following processes:

  • "%System%\WScript.exe" "%User Profile%\a7431n9057\sflhcteq.vbe"
  • %User Profile%\a7431n9057\sflhcteq.vbe
  • "%User Profile%\a7431n9057\dgrqqxt.exe" vhukr.xtv
  • dgrqqxt.exe vhukr.xtv
  • "schtasks.exe" /create /f /tn "DSL Subsystem" /xml "%User Temp%\tmpAF8F.tmp"
  • "schtasks.exe" /create /f /tn "DSL Subsystem Task" /xml "%User Temp%\tmpBCBA.tmp"

(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).. %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 creates the following folders:

  • %User Profile%\temp
  • %User Profile%\a7431n9057
  • %Application Data%\0EFADD19-2A94-41FB-8931-F2BBC5D61333\Logs\{username}
  • %Application Data%\0EFADD19-2A94-41FB-8931-F2BBC5D61333\Logs
  • %Application Data%\0EFADD19-2A94-41FB-8931-F2BBC5D61333
  • %Program Files%\DSL Subsystem
  • %System Root%\Users

(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).. %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000(32-bit), Server 2003(32-bit), XP, Vista(64-bit), 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit) , or C:\Program Files (x86) in Windows XP(64-bit), Vista(64-bit), 7(64-bit), 8(64-bit), 8.1(64-bit), 2008(64-bit), 2012(64-bit) and 10(64-bit).. %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.)

Other System Modifications

This Backdoor deletes the following files:

  • %Application Data%\0EFADD19-2A94-41FB-8931-F2BBC5D61333\DSL Subsystem\dslss.exe
  • %Application Data%\0EFADD19-2A94-41FB-8931-F2BBC5D61333\settings.bak
  • %Windows%\Tasks\DSL Subsystem Task.job
  • %Windows%\Tasks\DSL Subsystem.job
  • %User Temp%\RegSvcs.exe:Zone.Identifier

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Roaming 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 registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\
Microsoft\Windows\CurrentVersion\
Run
WindowsUpdate = "%User Profile%\A7431N~1\dgrqqxt.exe %User Profile%\A7431N~1\vhukr.xtv"

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\
Microsoft\Windows\CurrentVersion\
Run
AutoUpdate = "%User Profile%\A7431N~1\Update.vbs"

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\
Microsoft\Windows\CurrentVersion\
Run
DSL Subsystem = "%Program Files%\DSL Subsystem\dslss.exe"

Dropping Routine

This Backdoor drops the following files:

  • %User Profile%\a7431n9057\kxaghckuwc.exe
  • %Application Data%\0EFADD19-2A94-41FB-8931-F2BBC5D61333\run.dat
  • %User Profile%\a7431n9057\vhukr.xtv
  • %User Profile%\a7431n9057\dgrqqxt.exe
  • %User Profile%\a7431n9057\kkhrlrdp.cpl
  • %User Temp%\RegSvcs.exe
  • %User Profile%\a7431n9057\dilokapct.xl
  • %Application Data%\0EFADD19-2A94-41FB-8931-F2BBC5D61333\settings.bin
  • %User Profile%\a7431n9057\wvnehkaatw.cpl
  • %User Profile%\a7431n9057\Update.vbs
  • %User Profile%\a7431n9057\qfmlrd.nls
  • %User Profile%\a7431n9057\xwodx.xls
  • %User Profile%\a7431n9057\hiathcrexw.icm
  • %User Profile%\a7431n9057\agcatow.bin
  • %User Profile%\a7431n9057\okml.dat
  • %User Profile%\a7431n9057\dadxqr.nls
  • %User Profile%\temp\mtucrufe.txt
  • %Application Data%\0EFADD19-2A94-41FB-8931-F2BBC5D61333\task.dat
  • %User Profile%\a7431n9057\bdlaujwj.txt
  • %Program Files%\DSL Subsystem\dslss.exe
  • %User Profile%\a7431n9057\ndtgxqbj.xl
  • %User Profile%\a7431n9057\gdcielptcj.bmp
  • %User Profile%\a7431n9057\vlmmfsga.pdf
  • %User Profile%\a7431n9057\vtcbwves.bin
  • %User Profile%\a7431n9057\mtucrufe.txt
  • %User Profile%\a7431n9057\hhin.bmp
  • %User Profile%\a7431n9057\sflhcteq.vbe
  • %User Profile%\a7431n9057\apxvgojhni.cpl

(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).. %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %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).. %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000(32-bit), Server 2003(32-bit), XP, Vista(64-bit), 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit) , or C:\Program Files (x86) in Windows XP(64-bit), Vista(64-bit), 7(64-bit), 8(64-bit), 8.1(64-bit), 2008(64-bit), 2012(64-bit) and 10(64-bit).)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine: 9.850

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

Identify and terminate files detected as Backdoor.Win32.NANOCORE.TIAOODGW

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 3

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\Wow6432Node\Microsoft\Windows\CurrentVersion\Run
    • WindowsUpdate = "%User Profile%\A7431N~1\dgrqqxt.exe %User Profile%\A7431N~1\vhukr.xtv"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Run
    • AutoUpdate = "%User Profile%\A7431N~1\Update.vbs"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Run
    • DSL Subsystem = "%Program Files%\DSL Subsystem\dslss.exe"

Step 4

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.
  • %User Profile%\a7431n9057\kxaghckuwc.exe
  • %Application Data%\0EFADD19-2A94-41FB-8931-F2BBC5D61333\run.dat
  • %User Profile%\a7431n9057\vhukr.xtv
  • %User Profile%\a7431n9057\dgrqqxt.exe
  • %User Profile%\a7431n9057\kkhrlrdp.cpl
  • %User Temp%\RegSvcs.exe
  • %User Profile%\a7431n9057\dilokapct.xl
  • %Application Data%\0EFADD19-2A94-41FB-8931-F2BBC5D61333\settings.bin
  • %User Profile%\a7431n9057\wvnehkaatw.cpl
  • %User Profile%\a7431n9057\Update.vbs
  • %User Profile%\a7431n9057\qfmlrd.nls
  • %User Profile%\a7431n9057\xwodx.xls
  • %User Profile%\a7431n9057\hiathcrexw.icm
  • %User Profile%\a7431n9057\agcatow.bin
  • %User Profile%\a7431n9057\okml.dat
  • %User Profile%\a7431n9057\dadxqr.nls
  • %User Profile%\temp\mtucrufe.txt
  • %Application Data%\0EFADD19-2A94-41FB-8931-F2BBC5D61333\task.dat
  • %User Profile%\a7431n9057\bdlaujwj.txt
  • %Program Files%\DSL Subsystem\dslss.exe
  • %User Profile%\a7431n9057\ndtgxqbj.xl
  • %User Profile%\a7431n9057\gdcielptcj.bmp
  • %User Profile%\a7431n9057\vlmmfsga.pdf
  • %User Profile%\a7431n9057\vtcbwves.bin
  • %User Profile%\a7431n9057\mtucrufe.txt
  • %User Profile%\a7431n9057\hhin.bmp
  • %User Profile%\a7431n9057\sflhcteq.vbe
  • %User Profile%\a7431n9057\apxvgojhni.cpl

Step 5

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.
  • %User Profile%\temp
  • %User Profile%\a7431n9057
  • %Application Data%\0EFADD19-2A94-41FB-8931-F2BBC5D61333\Logs\{username}
  • %Application Data%\0EFADD19-2A94-41FB-8931-F2BBC5D61333\Logs
  • %Application Data%\0EFADD19-2A94-41FB-8931-F2BBC5D61333
  • %Program Files%\DSL Subsystem
  • %System Root%\Users

Step 6

Scan your computer with your Trend Micro product to delete files detected as Backdoor.Win32.NANOCORE.TIAOODGW. 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:

Step 7

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • %Application Data%\0EFADD19-2A94-41FB-8931-F2BBC5D61333\DSL Subsystem\dslss.exe
  • %Application Data%\0EFADD19-2A94-41FB-8931-F2BBC5D61333\settings.bak
  • %Windows%\Tasks\DSL Subsystem Task.job
  • %Windows%\Tasks\DSL Subsystem.job
  • %User Temp%\RegSvcs.exe:Zone.Identifier


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