Analysis by: RonJay Kristoffer Caragay
ALIASES:

Mal/DotNet-C (Sophos); Trojan-PSW.Win32.Chisburg.ifh (Kaspersky); Backdoor.Breut (Symantec)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet, Dropped by other malware

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.

It does not have any propagation routine.

It does not have any backdoor routine.

It executes the dropped file(s). As a result, malicious routines of the dropped files are exhibited on the affected system.

It does not have any information-stealing capability.

  TECHNICAL DETAILS

File Size: 658,944 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 01 Sep 2014
Payload: Drops files

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 drops the following copies of itself into the affected system:

  • %User Temp%\rundll11-.txt -deleted afterwards
  • %User Temp%\file.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, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

It drops and executes the following files:

  • %User Temp%\tmp.exe - detected as TSPY_CHISBURG.J
  • %User Temp%\notepad.exe -Microsoft .NET file (copy of applaunch.exe)
  • %User Temp%\mata.bat -detected as TROJ_RUNNER.GAU; runs %User Temp%\invs.vbs

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = "%User Temp%\file.exe"

Propagation

This Trojan does not have any propagation routine.

Backdoor Routine

This Trojan does not have any backdoor routine.

Dropping Routine

This Trojan drops the following files:

  • %User Temp%\invs.vbs ← deleted afterwards
  • %User Temp%\{random characters}.ini ← deleted afterwards
  • %User Temp%\mata2.bat ← use to copy %User Temp%\rundll11-.txt to %User Temp%\file.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, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

It executes the dropped file(s). As a result, malicious routines of the dropped files are exhibited on the affected system.

Information Theft

This Trojan does not have any information-stealing capability.

NOTES:

It does not have rootkit capabilities.

It does not exploit any vulnerability.

  SOLUTION

Minimum Scan Engine: 9.700
FIRST VSAPI PATTERN FILE: 11.122.05
FIRST VSAPI PATTERN DATE: 01 Sep 2014
VSAPI OPR PATTERN File: 11.123.00
VSAPI OPR PATTERN Date: 02 Sep 2014

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

Remove malware/grayware files dropped/downloaded by TROJ_MDOT.J. (Note: Please skip this step if the threats listed below have already been removed.)

  • TSPY_CHISBURG.J
  • TROJ_RUNNER.GAU

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_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Winlogon
    • Shell = %User Temp%\file.exe

Step 6

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.
  • %User Temp%\notepad.exe
  • %User Temp%\mata2.bat
  • %User Temp%\invs.vbs
  • %User Temp%\{random characters}.ini

Step 7

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