RTKT_DOTTUN.VTH

 Analysis by: Michelle Morales

 PLATFORM:

Windows

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

  • Threat Type: Others

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware

This malware may be dropped by other malware.

It also has rootkit capabilities, which enables it to hide its processes and files from the user.

It creates an event.

  TECHNICAL DETAILS

File Size:

385,024 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

20 Feb 2015

Payload:

Hides files and processes

Arrival Details

This malware may be dropped by the following malware:

Installation

This malware adds the following mutexes to ensure that only one of its copies runs at any one time:

  • prkMtx

Autostart Technique

This malware 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\CurrentControlSet\
Services\MSNDSRV
Options = "{hex values}"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\MSNDSRV
Config = "MSCFG32.EXE"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\MSNDSRV
Type = "1" --> this entry classifies the file as a kernel device driver

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\MSNDSRV
Start = "2" --> this entry allows the driver to be loaded or started automatically for all startups regardless of of type

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\MSNDSRV
2 = "F|\??\C:\Windows\system32\mscfg32.dll|F|\SystemRoot\system32\SPOOL2|F|\SystemRoot\system32\mslog32.dat|F|\??\C:\Windows\system32\mscfg32.dll"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\MSNDSRV
ErrorControl = "0" --> no error is displayed if the driver can't be loaded or started

It registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\MSNDSRV

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\MSNDSRV

Other System Modifications

This malware adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Session Manager\MemSubSys

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Session Manager\MemSubSys
{42E14DD3-F07A-78F1-7659-26AE141569AC-E0B3EE89} = "{hex values}"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Session Manager\MemSubSys
{A0CCDC61-7623-A425-7002-DB81F353945F-5A8ECFAD} = "{hex values}"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Session Manager\MemSubSys
1 = "{hex values}"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Session Manager\MemSubSys
I4 = "{hex values}"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Session Manager\MemSubSys
I1 = "{hex values}"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Session Manager\MemSubSys
I2 = "{hex values}"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Session Manager\MemSubSys
I3 = "{hex values}"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Session Manager\MemSubSys
I5 = "{hex values}"

Rootkit Capabilities

This malware also has rootkit capabilities, which enables it to hide its processes and files from the user.

Other Details

This malware drops the following file(s)/component(s):

  • %System%\MSDIRECTX.exe
  • %System%\MSCFG32.DLL
  • %System%\MSCFG32.EXE
  • %System%\drivers\MSNDSRV.SYS
  • %User Temp%\INSTV4.BAT

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.. %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

It creates the following event(s):

  • EE334FEA
  • BCAf8489
  • 95238543
  • D0385CB7-B834-45D1-1A1700E6C34E

NOTES:

The file %System%\MSDIRECTX.EXE opens the following events created by the main file:

  • EE334FEA
  • BCAf8489
  • 95238543

It also downloads a Certificate Revocation List (CRL) file from the following:

  • http://crl.microsoft.com/pki/crl/products/WinIntPCA.crl

This file is deleted by a batch file it creates. It also deletes itself.

The malware loads the driver (%System%\drivers\MSNDSRV.SYS) it created.This file is the one responsible for hooking System Service Dispatch Table (SSDT).

The file %User Temp%\INSTV4.BAT deletes the main file, and deletes itself afterwards.

  SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

11.490.04

FIRST VSAPI PATTERN DATE:

20 Feb 2015

VSAPI OPR PATTERN File:

11.491.00

VSAPI OPR PATTERN Date:

21 Feb 2015

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 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

Identify and delete files detected as RTKT_DOTTUN.VTH using either the Startup Disk or Recovery Console

[ Learn More ]

Step 4

Restart in Safe Mode

[ Learn More ]

Step 5

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.

  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSNDSRV
  • HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\MSNDSRV
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\MemSubSys

Step 6

Search and delete these files

[ 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%\MSDIRECTX.exe
  • %System%\MSCFG32.DLL
  • %System%\MSCFG32.EXE
  • %System%\drivers\MSNDSRV.SYS
  • %User Temp%\INSTV4.BAT

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as RTKT_DOTTUN.VTH. 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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