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Trojan.BAT.KILLAV.WLDT

June 04, 2021
 Analysis by: Maria Emreen Viray
 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • 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:

1,302 bytes

File Type:

BAT

Memory Resident:

No

Initial Samples Received Date:

13 Dec 2020

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:

  • net stop nkbkp
  • sc delete nkbkp
  • reg add HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\TMBMSRV /v Start /t REG_DWORD /d 3 /f
  • reg add HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\TmPfw /v Start /t REG_DWORD /d 3 /f
  • reg add HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\dsagent /v Start /t REG_DWORD /d 3 /f
  • reg add HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\tmlisten /v Start /t REG_DWORD /d 3 /f
  • reg add HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\TmProxy /v Start /t REG_DWORD /d 3 /f
  • reg add HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\ntrtscan /v Start /t REG_DWORD /d 3 /f
  • reg add HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\tmeevw /v Start /t REG_DWORD /d 3 /f
  • reg add HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\tmusa /v Start /t REG_DWORD /d 3 /f
  • reg add HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DSASvc /v Start /t REG_DWORD /d 3 /f
  • reg add HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\tmccfs /v Start /t REG_DWORD /d 3 /f
  • reg add HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WinDefend /v Start /t REG_DWORD /d 3 /f
  • bcdedit /deletevalue {current} safeboot
  • shutdown /r /f /t 00 & del %0
  • sc create nkbkp2 binpath= "%COMSPEC% /C start /b %Windows%\n.exe"

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

Other System Modifications

This Trojan modifies the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\TMBMSRV
Start = 3

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\TmPfw
Start = 3

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\dsagent
Start = 3

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\tmlisten
Start = 3

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\ntrtscan
Start = 3

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\tmeevw
Start = 3

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\tmusa
Start = 3

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\DSASvc
Start = 3

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\tmccfs
Start = 3

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\WinDefend
Start = 3

Other Details

This Trojan does the following:

  • stops and deletes the following service
    • nkbkp
  • creates the following service to execute %Windows%\n.exe → detected as Ransom.Win64.MEDUSALOCKER.AA
    • Service Name: nkbkp2
    • ImagePath: "%COMSPEC% /C start /b %Windows%\n.exe"
  • disables Automatic Start for the following AV services by setting it to Manual Start:
    • TMBMSRV
    • TmPfw
    • dsagent
    • tmlisten
    • TmProxy
    • ntrtscan
    • tmeevw
    • tmusa
    • DSASvc
    • tmccfs
    • WinDefend
    Note: registry key is created if service does not exists
  • restarts machine into normal mode
  • deletes itself

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

16.754.06

FIRST VSAPI PATTERN DATE:

01 Jun 2021

VSAPI OPR PATTERN File:

16.755.00

VSAPI OPR PATTERN Date:

02 Jun 2021

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

Restore this modified 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\SYSTEM\ControlSet001\services\TMBMSRV
    • Start = 3 → 2
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\TmPfw
    • Start = 3 → 2
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\dsagent
    • Start = 3 → 2
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\tmlisten
    • Start = 3 → 2
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\TmProxy
    • Start = 3 → 2
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\ntrtscan
    • Start = 3 → 2
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\tmeevw
    • Start = 3 → 2
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\tmusa
    • Start = 3 → 2
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\DSASvc
    • Start = 3 → 2
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\tmccfs
    • Start = 3 → 2
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\WinDefend
    • Start = 3 → 2

Step 4

Delete this registry key

[ 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\SYSTEM\CurrentControlSet\services\nkbkp2

Step 5

Scan your computer with your Trend Micro product to delete files detected as Trojan.BAT.KILLAV.WLDT. 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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