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WORM_CONUSTR.V

February 23, 2017
 Analysis by: John Anthony Banes
 ALIASES:

Worm.Win32.Conustr (Ikarus); W32/Conustr-A (Sophos)

 PLATFORM:

Windows

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet, Via physical/removable drives


This worm arrives via removable drives. It 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 backdoor routine.

  TECHNICAL DETAILS

File Size:

139,264 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

30 Jan 2017

Payload:

Drops files, Steals information

Arrival Details

This worm arrives via removable drives.

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 worm drops the following copies of itself into the affected system and executes them:

  • %User Temp%\conhost.exe

(Note: %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 drops and executes the following files:

  • %User Temp%\ppxxxx - contains registry data to be added to the machine
  • %User Temp%\must.bat - batch file containing commands used to gather information

(Note: %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 folders:

  • {Removable Drive Letter}:\RECYCLER
  • %User Temp%\Media
  • %User Temp%\WPDNSE

(Note: %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.)

Other System Modifications

This worm adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
exefile
NeverShowExt = ""

It modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Windows
Load = "%User Temp%\conhost.exe"

(Note: The default value data of the said registry entry is "".)

Propagation

This worm drops the following copies of itself in all physical and removable drives:

  • {Removable Drive Letter}:\{Original Folder Name}.exe
  • {Removable Drive Letter}:\RECYCLER\Dcfly.exe

Backdoor Routine

This worm does not have any backdoor routine.

Dropping Routine

This worm drops the following files:

  • %User Temp%\WPDNSE\{random filename}.NLS - password protected archive file containing the following files:
    • %User Temp%\winword4.doc
    • DOC, DOCX, PDF, MVD, TIF, XLS, and XLSX files modified after November 23, 2016 found inside the machine's drives
  • {Removable Drive Letter}:\RECYCLER\{random filename}.ldf
  • {Removable Drive Letter}:\RECYCLER\{random filename}.NLS - copy of %User Temp%\WPDNSE\{random filename}.NLS
  • %User Temp%\Media\{random filename}.ldf - contains BD SQL transaction log file

(Note: %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.)

Information Theft

This worm gathers the following data:

  • BD SQL transaction log file
  • Microsoft Word Document Files
  • Microsoft Excel Document Files
  • MindView Document Files
  • Portable Document Files
  • Tagged Image Format Files
  • System Date
  • OS version information
  • List of user accounts
  • List of administrator accounts
  • Running services
  • Active TCP connections
  • Running applications and services
  • Full network configuration for all adapters
  • Contents of the ARP cache
  • System Information
  • List of network connections
  • List of computers in the current domain
  • List all domains in the network
  • List of all users of each domain
  • List of files and directories of drives C:\, D:\, E:\, F:\, G:\, H:\, I:\

Stolen Information

This worm saves the stolen information in the following file:

  • %User Temp%\winword4.doc

(Note: %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.)

Other Details

This worm does the following:

  • This malware uses a folder icon to disguise itself.
  • It also drops copies of itself using the original folder names in the removable drive. Then it hides the original folders to trick the users into clicking its dropped copy.
  • It uses the password "ThisTw0Piece" for the archive file it creates.

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

13.196.05

FIRST VSAPI PATTERN DATE:

02 Feb 2017

VSAPI OPR PATTERN File:

13.197.00

VSAPI OPR PATTERN Date:

03 Feb 2017

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

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\Classes\exefile
    • NeverShowExt = ""

Step 5

Restore this modified registry value

[ 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_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows
    • From: Load = "%User Temp%\conhost.exe"
      To: Load = ""

Step 6

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 Letter}:\RECYCLER
  • %User Temp%\Media
  • %User Temp%\WPDNSE

Step 7

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.
  • %User Temp%\ppxxxx
  • %User Temp%\winword4.doc
  • %User Temp%\must.bat

Step 8

  1. Open a command prompt.
    • For Windows 2000, Windows XP, and Windows Server 2003 users, click Start>Run. In the Search box, type CMD then press Enter.
    • For Windows Vista, Windows 7, and Windows Server 2008 users, click Start, type CMD in the Search input field then press Enter.
    • For Windows 8, Windows 8.1, and Windows Server 2012 users, right-click on the lower-left corner of the screen, click Command Prompt.
  2. In the CMD console, type the following:

    ATTRIB [+R | -R] [+A | -A ] [+S | -S] [+H | -H] [+I | -I] [drive:][path][file name] [/S [/D] [/L]]

    Where:
    + Sets an attribute.
    - Clears an attribute
    R Read-only file attribute
    A Archive file attribute
    S System file attribute
    H Hidden file attribute
    I Not content indexed file attribute
    [drive:][path][filename]
    Specifies a file or files for attrib to process
    /S Processes matching files in the current folder and all subfolders.
    /D Processes folders
    /L Work on the attributes of the Symbolic Link versus the target of the Symbolic Link
    Example:
    To unhide all files and folders (including subfolders) in drive D:
    ATTRIB –H D:\* /S /D
  3. Repeat Step 3 for folders and files in other drives or folders.

Step 9

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