Backdoor.Win32.NANOCORE.TIAOODHJ

June 03, 2020
 Analysis by: Mohammed Malubay
 ALIASES:

RAR/Agent.DA trojan (NOD32);

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet

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.

It does not have any propagation routine.

It executes commands from a remote malicious user, effectively compromising the affected system.

  TECHNICAL DETAILS

File Size:

1,237,931 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

02 Jun 2020

Payload:

Connects to URLs/IPs, Steals information

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 folders:

  • %System Root%\s8244g2624

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

It drops the following files:

  • %System Root%\s8244g2624\bfhcalitf.dll
  • %System Root%\s8244g2624\bnxa.jpg
  • %System Root%\s8244g2624\cnhdo.exe
  • %System Root%\s8244g2624\cwid.xl
  • %System Root%\s8244g2624\fgriaet.bin
  • %System Root%\s8244g2624\hkgqsqmv.dat
  • %System Root%\s8244g2624\hltmmoo.ppt
  • %System Root%\s8244g2624\ikmxegbbxs.xls
  • %System Root%\s8244g2624\ixogm.bin
  • %System Root%\s8244g2624\jjxinvqmu.bmp
  • %System Root%\s8244g2624\jxjou.bin
  • %System Root%\s8244g2624\khgmv.docx
  • %System Root%\s8244g2624\ltta.dll
  • %System Root%\s8244g2624\nutf.bmp
  • %System Root%\s8244g2624\nuucdr.jpg
  • %System Root%\s8244g2624\oqwoq.docx
  • %System Root%\s8244g2624\pagcm.bin
  • %System Root%\s8244g2624\qnvuikct.xls
  • %System Root%\s8244g2624\rntu.icm
  • %System Root%\s8244g2624\usbmhtm.xl
  • %System Root%\s8244g2624\wlteqct.dll
  • %System Root%\s8244g2624\xfqafg.vbs
  • %System Root%\s8244g2624\gacgt.exe → modified executable that runs AutoIt script executed later at runtime
  • %System Root%\s8244g2624\Update.vbs
  • %System Root%\s8244g2624\kjls.vgv
  • %User Profile%\temp\jxjou.bin
  • %User Temp%\tmpC86C.tmp → xml file for scheduled task
  • %Application Data%\{GUID}\run.dat
  • %Application Data%\{GUID}\task.dat
  • %Application Data%\{GUID}\catalog.dat
  • %Application Data%\{GUID}\storage.dat
  • %Application Data%\{GUID}\settings.bin
  • %Application Data%\{GUID}\Logs\{user name}\KB_{random characters}.dat
  • %User Temp%\RegSvcs.exe → copy of legitimate Regsvcs.exe (.NET Services Installation Tool)

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

It adds the following processes:

  • "%System Root%\s8244g2624\gacgt.exe" kjls.vgv
  • "%User Temp%\RegSvcs.exe"

(Note: %System Root% is the Windows root folder, where it usually is C:\ 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 mutexes to ensure that only one of its copies runs at any one time:

  • Global\{GUID}

Autostart Technique

This Backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Chrome = %System Root%\S8244G~1\gacgt.exe %System Root%\S8244G~1\kjls.vgv

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
AutoUpdate = %System Root%\S8244G~1\Update.vbs

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\
Microsoft\Windows\CurrentVersion\
Run
Chrome = %System Root%\S8244G~1\gacgt.exe %System Root%\S8244G~1\kjls.vgv

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\
Microsoft\Windows\CurrentVersion\
Run
AutoUpdate = %System Root%\S8244G~1\Update.vbs

Propagation

This Backdoor does not have any propagation routine.

Backdoor Routine

This Backdoor executes the following commands from a remote malicious user:

  • Manage its backdoor file:
    • Update itself
    • Restart itself
    • Terminate itself
    • Uninstall itself
    • Restart connection
    • Disconnect
    • Disable/Restore Protection
  • System Control:
    • Restart machine
    • Shutdown machine
    • Lock machine
    • Browse files and folders
    • Task Manager
    • Edit registry
    • Remote console (Command Prompt)
    • Remote execute a file
    • Remote execute a script (Batch, HTML, VBS, Python, Java, PHP)
    • Remote control the machine
    • Remote control mouse
    • Recover browser passwords
    • Log Keystrokes
    • View the screen/webcam
    • Listen to audio/microphone
    • Send Messages / Chat with the malicious user
    • Swap/Unswap mouse buttons
    • Open/Close CD/DVD Tray

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • {BLOCKED}.{BLOCKED}.225.111:64853
  • strongods.{BLOCKED}s.net:64853

Rootkit Capabilities

This Backdoor does not have rootkit capabilities.

Information Theft

This Backdoor gathers the following data:

  • Computer Name
  • User Name
  • CPU Usage
  • Available and Free Memory
  • Active Window Title
  • Operating System Version
  • System Type (32-bit or 64-bit)
  • Malware Filename
  • Installed Anti-Virus/Anti-Spyware

Other Details

This Backdoor does the following:

  • {String 1} can be one of the following:
    • AGP
    • ARP
    • DDP
    • DHCP
    • DNS
    • DOS
    • DPI
    • DSL
    • IMAP
    • ISS
    • LAN
    • NAS
    • NAT
    • NTFS
    • PCI
    • SAAS
    • SCSI
    • SMTP
    • TCP
    • UDP
    • UPNP
    • WAN
    • WPA
  • {String 2} can be one of the following:
    • Host
    • Manager
    • Monitor
    • Service
    • Subsystem

It does not exploit any vulnerability.

It adds the following scheduled tasks:

  • Task Name: {String 1} {String 2}
    • Task Settings: {based on %User Temp%\tmpC86C.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).)

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.906.05

FIRST VSAPI PATTERN DATE:

02 Jun 2020

VSAPI OPR PATTERN File:

15.907.00

VSAPI OPR PATTERN Date:

03 Jun 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:

     
  • Troj.Win32.TRX.XXPE50FSX001

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

Restart in Safe Mode

[ Learn More ]

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\Microsoft\Windows\CurrentVersion\Run
    • Chrome = %System Root%\S8244G~1\gacgt.exe %System Root%\S8244G~1\kjls.vgv
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • AutoUpdate = %System Root%\S8244G~1\Update.vbs
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Run
    • Chrome = %System Root%\S8244G~1\gacgt.exe %System Root%\S8244G~1\kjls.vgv
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Run
    • AutoUpdate = %System Root%\S8244G~1\Update.vbs

Step 6

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.
  • %System Root%\s8244g2624\bfhcalitf.dll
  • %System Root%\s8244g2624\bnxa.jpg
  • %System Root%\s8244g2624\cnhdo.exe
  • %System Root%\s8244g2624\cwid.xl
  • %System Root%\s8244g2624\fgriaet.bin
  • %System Root%\s8244g2624\hkgqsqmv.dat
  • %System Root%\s8244g2624\hltmmoo.ppt
  • %System Root%\s8244g2624\ikmxegbbxs.xls
  • %System Root%\s8244g2624\ixogm.bin
  • %System Root%\s8244g2624\jjxinvqmu.bmp
  • %System Root%\s8244g2624\jxjou.bin
  • %System Root%\s8244g2624\khgmv.docx
  • %System Root%\s8244g2624\ltta.dll
  • %System Root%\s8244g2624\nutf.bmp
  • %System Root%\s8244g2624\nuucdr.jpg
  • %System Root%\s8244g2624\oqwoq.docx
  • %System Root%\s8244g2624\pagcm.bin
  • %System Root%\s8244g2624\qnvuikct.xls
  • %System Root%\s8244g2624\rntu.icm
  • %System Root%\s8244g2624\usbmhtm.xl
  • %System Root%\s8244g2624\wlteqct.dll
  • %System Root%\s8244g2624\xfqafg.vbs
  • %System Root%\s8244g2624\gacgt.exe
  • %System Root%\s8244g2624\Update.vbs
  • %System Root%\s8244g2624\kjls.vgv
  • %User Profile%\temp\jxjou.bin
  • %User Temp%\tmpC86C.tmp
  • %Application Data%\{GUID}\run.dat
  • %Application Data%\{GUID}\task.dat
  • %Application Data%\{GUID}\catalog.dat
  • %Application Data%\{GUID}\storage.dat
  • %Application Data%\{GUID}\settings.bin
  • %Application Data%\{GUID}\Logs\{user name}\KB_{random characters}.dat
  • %User Temp%\RegSvcs.exe

Step 7

Search and delete this folder

[ 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.
  • %System Root%\s8244g2624

Step 8

Delete the Scheduled Tasks added by this malware/grayware

[ Learn More ]

To delete the added Scheduled Task file:

For Windows 7, Windows Server 2008 (R2), Windows 8, Windows 8.1, Windows 10, and Windows Server 2012 (R2):

  1. Open the Windows Task Scheduler. To do this:
    • On Windows 7, and Windows Server 2008 (R2), click Start, type taskschd.msc in the Search input field, then press Enter.
    • On Windows 8, Windows 8.1, 10 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 of the Task Scheduler Window, click Task Scheduler Library.
  3. In the upper-middle panel, click a Task.
  4. In the lower middle panel, click the Actions tab
  5. Check if the malware path and file name exists in the task. To do this, check the value in the Details column under the Actions tab.
  6. If found, select the task and press DELETE and click Yes to delete the task.
  7. Repeat the steps above for the remaining tasks.

Step 9

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Backdoor.Win32.NANOCORE.TIAOODHJ. 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 10

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