Trojan.VBS.MALXMR.THEBIBO

 Analysis by: Joshua Paul Ignacio

 ALIASES:

Trojan.VBS.Obfuscated (IKARUS); VBS/Obfuscated.AF trojan (NOD32)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Spammed via email

This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users. It 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:

191,179 bytes

File Type:

HTA

Memory Resident:

No

Initial Samples Received Date:

29 May 2020

Payload:

Downloads files

Arrival Details

This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

It 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:

It adds the following processes:

  • uac {%User Temp%\CMSTP.inf} {Command to execute} (For Windows 10 only)

(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 Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
CheckIN = powershell -exec bypass -windowStyle hidden -enc {Content of %Public%\Libraries\Content}

Propagation

The said .INF file contains the following strings:

[version]
Signature=`$chicago`$
AdvancedINF=2.5

[DefaultInstall]
CustomDestination=CustInstDestSectionAllUsers
RunPreSetupCommands=RunPreSetupCommandsSection

[RunPreSetupCommandsSection]
; Commands Here will be run Before Setup Begins to install
{Command to execute}
taskkill /IM cmstp.exe /F

[CustInstDestSectionAllUsers]
49000,49001=AllUSer_LDIDSection, 7

[AllUSer_LDIDSection]
"HKLM", "SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\CMMGR32.EXE", "ProfileInstallPath", "%UnexpectedError%", ""

[Strings]
ServiceName="CorpVPN"
ShortSvcName="CorpVPN"

Download Routine

This Trojan connects to the following URL(s) to download its component file(s):

  • https://{BLOCKED}d.ly/Firts
    • redirects to: http://{BLOCKED}xrkbiepyylgdcwrcjimxnfsrbgravivgbannnpnubawpdvekzbdbuqrd.{BLOCKED}.com.ua/uac.txt

Other Details

This Trojan does the following:

  • For Windows 7, it will bypass UAC (User Access Control) by using the Invoke-PsUACme method by using the following parameters:
    • -Payload {Command to execute}
    • -CustomDLL32 {DLL to be used for "method" parameter}
    • -CustomDLL64 {DLL to be used for "method" parameter}
      • If CustomDLL32 and/or CustomDLL64 parameters are not used, it will used the hard-coded DLLs on the script instead.
    • -method
      • method types:
        • Sysrep
        • OOBE
        • ActionQueue
        • migwiz
        • cliconfg
        • winsat
        • mmc
  • For every "method" type used, the contents of the DLL stated on "CustomDLL32/64" parameters or the hard-coded DLL will be written on a created DLL file under %User Temp% in which the name will depend on the "method" type and Windows Build Version.
  • The contents of the created DLL file will then be copied to a created file %User Temp%\uac.cab
  • It will then extract the contents of %User Temp%\uac.cab on a directory using wusa then executes a program that will load the created DLL with elevated privileges.
  • The directory where the contents of %User Temp%\uac.cab will be extracted and executed program are also dependent on the method type used.
  • Below are the following DLL Name, Directory and Executed pragram for each method type and Windows OS Build Version:
    • For Windows 7 and Windows Server 2008 only:
      • Method type: Sysprep
        • DLL Name: %User Temp%\CRYPTBASE.dll
        • Directory: %System%\Sysprep\
        • Executed Program: %System%\Sysprep\sysprep.exe
      • Method type: ActionQueue
        • DLL Name: %User Temp%\ActionQueue.dll
        • Directory: %System%\Sysprep\
        • Executed Program: %System%\Sysprep\sysprep.exe
      • Method type: winsat
        • DLL Name: %User Temp%\ntwdblib.dll
        • Directory: %System%\Sysprep\
        • Executed Program: %System%\Sysprep\winsat.exe
      • Method type: mmc
        • DLL Name: %User Temp%\ntwdblib.dll
        • Directory: %System%\
        • Executed Program: %System%\mmc.exe
    • For Windows 8.1 and Windows Server 2012 only:
      • Method type: Sysprep
        • DLL Name: %User Temp%\shcore.dll
        • Directory: %System%\Sysprep\
        • Executed Program: %System%\Sysprep\sysprep.exe
      • Method type: winsat
        • DLL Name: %User Temp%\devobj.dll
        • Directory: %System%\Sysprep\
        • Executed Program: %System%\Sysprep\winsat.exe
      • Method type: mmc
        • DLL Name: %User Temp%\elsext.dll
        • Directory: %System%\
        • Executed Program: %System%\mmc.exe
    • For both Windows OS Build Versions:
      • Method type: OOBE
        • DLL Name: %User Temp%\wdscore.dll
        • Directory: %System%\oobe\
        • Executed Program: %System%\oobe\setupsqm.exe
      • Method type: migwiz
        • DLL Name: %User Temp%\wdscore.dll
        • Directory: %System%\migwiz\
        • Executed Program: %System%\Sysprep\migwiz.exe
      • Method type: cliconfg
        • DLL Name: %User Temp%\ntwdblib.dll
        • Directory: %System%\
        • Executed Program: %System%\cliconfg.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).. %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.904.06

FIRST VSAPI PATTERN DATE:

29 May 2020

VSAPI OPR PATTERN File:

15.905.00

VSAPI OPR PATTERN Date:

30 May 2020

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

[ Learn More ]

Step 4

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
    • CheckIN = powershell -exec bypass -windowStyle hidden -enc {Content of %Public%\Libraries\Content}

Step 5

Search and delete these files

[ Learn More ]
There may be some component 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.
  • %Public%\Libraries\Content
  • %Public%\Libraries\reg.bat
  • %User Temp%\CMSTP.inf (For Windows 10 only)
  • %User Temp%\CRYPTBASE.dll
  • %User Temp%\ActionQueue.dll
  • %User Temp%\ntwdblib.dll
  • %User Temp%\shcore.dll
  • %User Temp%\devobj.dll
  • %User Temp%\elsext.dll
  • %User Temp%\wdscore.dll

Step 6

Scan your computer with your Trend Micro product to delete files detected as Trojan.VBS.MALXMR.THEBIBO. 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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