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WORM_DORKBOT.KX

April 08, 2013
 Analysis by: Rika Joi Gregorio
 ALIASES:

VirTool:Win32/VBInject(Microsoft), Win32/Dorkbot.A worm(Eset)

 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:

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size:

135,168 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

04 Apr 2013

Arrival Details

This worm 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:

  • %Application Data%\{random}.exe - will be deleted afterwards

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.)

It drops the following files:

  • {Drive Letter}:\BOOTEX.LOG
  • {Drive Letter}:\BOOTEX.LOG.LNK
  • {Drive Letter}:\.Trashes\Desktop.ini
  • {Drive Letter}:\{folder name}.lnk - if the removable drive contains folder
  • {Drive Letter}:\{file name}.lnk - if the removable drive contains file

Propagation

This worm creates the following folders in all removable drives:

  • {Drive Letter}:\.Trashes

It drops the following copy(ies) of itself in all removable drives:

  • {Drive Letter}:\.Trashes\{random}.com
  • {Drive Letter}:\{random}.exe

Other Details

This worm connects to the following possibly malicious URL:

  • http://{BLOCKED}.{BLOCKED}.246.75/6510.exe
  • {BLOCKED}e.{BLOCKED}x.com

It deletes the initially executed copy of itself

NOTES:

This worm drops shortcut files pointing to the copy of itself in removable drives. These dropped .LNK files use the names of the files and folders located on the said drives for their file names.

It then sets the attributes of the original files/folders to Hidden to trick the user into clicking the .LNK files.

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

9.838.02

FIRST VSAPI PATTERN DATE:

05 Apr 2013

VSAPI OPR PATTERN File:

9.839.00

VSAPI OPR PATTERN Date:

06 Apr 2013

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

Restart in Safe Mode

[ Learn More ]

Step 3

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.  
  • {Drive Letter}:\.Trashes

Step 4

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.
  • {Drive Letter}:\BOOTEX.LOG
  • {Drive Letter}:\BOOTEX.LOG.LNK
  • {Drive Letter}:\{folder name}.lnk
  • {Drive Letter}:\{file name}.lnk

Step 5

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