Coinminer.VBS.MALBTC.AA

July 26, 2019
 Analysis by: Wilbert Luy
 ALIASES:

VBS/Agent.NOS worm (NOD32)

 PLATFORM:

Windows

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

  • Threat Type: Coinminer

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This Coinminer 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:

111,800 bytes

File Type:

VBS

Memory Resident:

Yes

Initial Samples Received Date:

04 Apr 2019

Arrival Details

This Coinminer 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 Coinminer drops the following files:

  • %System%\DM6331.TMP
  • %System Root%\Users\All Users\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup\win.vbs
  • %System Root%\Users\All Users\AppData\Local\Temp\DM6331.TMP
  • %System Root%\Users\All Users\AppData\Local\Temp\rknrl.vbs
  • %System Root%\Users\Default\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup\win.vbs
  • %System Root%\Users\Default\AppData\Local\Temp\DM6331.TMP
  • %System Root%\Users\Default\AppData\Local\Temp\rknrl.vbs
  • %System Root%\Users\Default User\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup\win.vbs
  • %System Root%\Users\Public\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup\win.vbs
  • %System Root%\Users\Public\AppData\Local\Temp\DM6331.TMP
  • %System Root%\Users\Public\AppData\Local\Temp\rknrl.vbs
  • %User Temp%\DM6331.TMP
  • %User Temp%\DM6332.TMP
  • %User Temp%\Cab3E7.tmp
  • %User Temp%\Tar3E7
  • %User Temp%\rad{random}.tmp
  • %User Temp%\winstart\__tmp_rar_sfx_access_check_1556016
  • %System Root%\DM6331.TMP
  • %System Root%\autoexec.vbs
  • %Program Files%\Microsoft Office\Office12\Normal.doc
  • %Program Files%\Microsoft Office\Office12\Book.xls
  • %User Temp%\rknrl.TMP1
  • %User Temp%\rknrl.TMP2
  • %Common Programs%\Microsoft Office\Microsoft Office Word 2007.lnk
  • {Removable Drive}:\Recycle\DM6331.TMP
  • {Removable Drive}:\Recycle\rkrl.vbs
  • {Removable Drive}:\Recycle\rknrl.TMP1
  • {Removable Drive}:\Recycle\rknrl.TMP2
  • {Removable Drive}:\{Directory Name}.lnk

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.. %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).. %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).. %Common Programs% is the folder that contains common program groups for all users, which is usually C:\Documents and Settings\All Users\Start Menu\Programs on Windows 2000, XP, and Server 2003, or C:\ProgramData\Microsoft\Windows\Start Menu\Programs on Windows Vista, 7, and 8.)

It drops and executes the following files:

  • %User Temp%\winstart\miner.exe
  • %User Temp%\winstart\myminer.exe
  • %User Temp%\winstart.vbs
  • %User Temp%\rknrl.vbs
  • %Windows%\TEMP\winstart.vbs
  • %Windows%\TEMP\rknrl.vbs

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

It adds the following processes:

  • %System%\wscript.exe //B "%User Temp%\rknrl.vbs"
  • %System%\wscript.exe //B "%User Temp%\winstart.vbs"
  • %System%\taskkill.exe /f /im miner.exe
  • %System%\taskkill.exe /f /im myminer.exe
  • %System%\taskkill.exe /f /im myminera.exe
  • %System%\taskkill.exe /f /im myminern.exe
  • %System%\cmd.exe /c del winstart\miner.exe /s /q
  • %System%\cmd.exe /c del "%User Temp%\winstart\miner.exe"
  • %User Temp%\winstart\myminer.exe

(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).)

Autostart Technique

This Coinminer registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\MsRkNrL

Other System Modifications

This Coinminer adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
rknrl

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
rknrl\ctrlHost

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
rknrl\miner

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\MsRkNrL

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
rknrl\ctrlHost
hCount = "-1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
rknrl\miner
app = "myminer.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
rknrl
miner = "{base64 encoded string}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
rknrl\miner
order = "{base64 encoded string}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
rknrl\ctrlHost
H1 = "{alpha numeric}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
rknrl\ctrlHost
H2 = "{alpha numeric}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
rknrl\ctrlHost
hCount = "2"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
rknrl\ctrlHost
geth = "{alpha numeric}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
rknrl
officePath = "%Program Files%\Microsoft Office\Office12\"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
rknrl
officeversion = "12.0"

HKEY_CURRENT_USER\Software\Microsoft\
Office\12.0\Word\
Options
DefaultFormat = "Doc"

HKEY_CURRENT_USER\Software\Microsoft\
Office\12.0\Word\
Security
VBAWarnings = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Office\12.0\Word\
Security
Level = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Office\12.0\Excel\
Security
Level = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Office\12.0\Excel\
Options
DefaultFormat = "56"

HKEY_CURRENT_USER\Software\Microsoft\
Office\12.0\Excel\
Secuirty
VBAWarnings = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
rknrl
Path = "%User Temp%\"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
rknrl
startup = "%User Startup%\"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
rknrl
currentuser = "{User Name}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
rknrl
runstatus = "ser"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
winstart = "wscript.exe //B rknrl.vbs"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\MsRkNrL
Type = "16"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\MsRkNrL
start = "2"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\MsRkNrL
ErrorControl = "2"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\MsRkNrL
ImagePath = "%systemroot%\system32\wscript.exe //B C:\autoexec.vbs"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\MsRkNrL
DisplayName = "MicrosoftPassportContainer"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\MsRkNrL
ObjectName = "LocalSystem"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
rknrl
ver = "web1|miner1|vbs1|doc1|xls1|"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
rknrl
Timer = "{Incrementing Time}"

It modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
ProxyEnable = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
ProxyServer = "http={BLOCKED}.{BLOCKED}.0.1:8888;https={BLOCKED}.{BLOCKED}.0.1:8888"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
ProxyOverride = "<-loopback>"

Propagation

This Coinminer creates the following folders in all removable drives:

  • {Removable Drive}:\RECYCL

Other Details

This Coinminer connects to the following possibly malicious URL:

  • raw.{BLOCKED}ntent.com
  • aigoingtokill.{BLOCKED}eworld.com
  • airobotheworld.{BLOCKED}tokill.com
  • newtogo.{BLOCKED}orld.com
  • aigoingtokill.{BLOCKED}tokill.club
  • api.{BLOCKED}can.io

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.918.03

FIRST VSAPI PATTERN DATE:

04 Apr 2019

VSAPI OPR PATTERN File:

14.919.00

VSAPI OPR PATTERN Date:

05 Apr 2019

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

Restart in Safe Mode, and then 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\SYSTEM\ControlSet001\services
    • MsRkNrL

Step 4

Identify and terminate files detected as Coinminer.VBS.MALBTC.AA

[ 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 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
    • winstart = "wscript.exe //B rknrl.vbs"

Step 6

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\Microsoft
    • rknrl

Step 7

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_CURRENT_USER\Software\Microsoft\Office\12.0\Word\Options
    • DefaultFormat = "Doc"
  • In HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Word\Options
    • DefaultFormat = "{Default Value}"
  • In HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Word\Security
    • VBAWarnings = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Word\Security
    • VBAWarnings = "{Default Value}"
  • In HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Word\Security
    • Level = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Word\Security
    • Level = "{Default Value}"
  • In HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Excel\Security
    • Level = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Excel\Security
    • Level = "{Default Value}"
  • In HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Excel\Options
    • DefaultFormat = "56"
  • In HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Excel\Options
    • DefaultFormat = "{Default Value}"
  • In HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Excel\Security
    • VBAWarnings = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Excel\Security
    • VBAWarnings = "{Default Value}"

Step 8

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.
  • {Removable Drive}:\RECYCL

Step 9

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%\DM6331.TMP
  • %User Temp%\DM6332.TMP
  • %User Temp%\Cab3E7.tmp
  • %User Temp%\Tar3E7
  • %User Temp%\rad{random}.tmp
  • %User Temp%\winstart\__tmp_rar_sfx_access_check_1556016
  • %System Root%\DM6331.TMP
  • %System Root%\autoexec.vbs
  • %Program Files%\Microsoft Office\Office12\Normal.doc
  • %Program Files%\Microsoft Office\Office12\Book.xls
  • %User Temp%\rknrl.TMP1
  • %User Temp%\rknrl.TMP2
  • %Common Programs%\Microsoft Office\Microsoft Office Word 2007.lnk
  • {Removable Drive}:\Recycle\DM6331.TMP
  • {Removable Drive}:\Recycle\rkrl.vbs
  • {Removable Drive}:\Recycle\rknrl.TMP1
  • {Removable Drive}:\Recycle\rknrl.TMP2
  • {Removable Drive}:\{Directory Name}.lnk
  • %System%\DM6331.TMP
  • %System Root%\Users\All Users\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup\win.vbs
  • %System Root%\Users\All Users\AppData\Local\Temp\DM6331.TMP
  • %System Root%\Users\All Users\AppData\Local\Temp\rknrl.vbs
  • %System Root%\Users\Default\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup\win.vbs
  • %System Root%\Users\Default\AppData\Local\Temp\DM6331.TMP
  • %System Root%\Users\Default\AppData\Local\Temp\rknrl.vbs
  • %System Root%\Users\Default User\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup\win.vbs
  • %System Root%\Users\Public\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup\win.vbs
  • %System Root%\Users\Public\AppData\Local\Temp\DM6331.TMP
  • %System Root%\Users\Public\AppData\Local\Temp\rknrl.vbs
  • %User Temp%\winstart\miner.exe
  • %User Temp%\winstart\myminer.exe
  • %User Temp%\winstart.vbs
  • %User Temp%\rknrl.vbs
  • %Windows%\TEMP\winstart.vbs
  • %Windows%\TEMP\rknrl.vbs

Step 10

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Coinminer.VBS.MALBTC.AA. 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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