WORM_DORKBOT.MB


 ALIASES:

Worm:Win32/Dorkbot.A(Microsoft),Worm.Win32.Dorkbot(Sunbelt),Trojan.Generic.KDV.833887(Bitdefender),Win32/Dorkbot.B worm(Nod32)

 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 by connecting affected removable drives to a system. 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 drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size:

169,991 bytes

File Type:

, EXE

Memory Resident:

Yes

Initial Samples Received Date:

27 Apr 2013

Arrival Details

This worm arrives by connecting affected removable drives to a system.

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:

  • %Application Data%\{Random File Name}.exe

(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.)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{Random File Name} = "%Application%\{Random File Name}.exe"

Propagation

This worm creates the following folders in all removable drives:

  • {Removable Drive}:\RECYCLER

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

  • {Removable Drive}:\RECYCLER\{Random File Name}.exe

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

The said .INF file contains the following strings:

[AutoRun]
{GARBAGE_CHARACTERS}
shellexecute=RECYCLER\{Random File Name}.exe
{GARBAGE_CHARACTERS}
icon=shell32.dll,7
{GARBAGE_CHARACTERS}
shell\open\command=RECYCLER\{Random File Name}.exe
{GARBAGE_CHARACTERS}
action=Open folder to view files
{GARBAGE_CHARACTERS}
shell\explore\command=RECYCLER\{Random File Name}.exe
{GARBAGE_CHARACTERS}
useautoplay=1

Other Details

This worm connects to the following URL(s) to get the affected system's IP address:

  • http://api.wipmania.com

It deletes the initially executed copy of itself

NOTES:

It drops the file {Removable Drive}:\RECYCLER\Desktop.ini to change the icon of the RECYCLER folder into the Recycle Bin icon.

It drops shortcut files pointing to the copy of itself in removable drives. These dropped .LNK files use the names of the folders located on the said drives for their file names. It then sets the attributes of the original folders to Hidden to trick the user into clicking the .LNK files.

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

9.882.02

FIRST VSAPI PATTERN DATE:

17 Jan 2013

VSAPI OPR PATTERN File:

9.883.00

VSAPI OPR PATTERN Date:

18 Jan 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

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\CurrentVersion\Run
    • {Random File Name} = "%Application%\{Random File Name}.exe"

Step 4

Search and delete this folder

[ 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}:\RECYCLER

Step 5

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.
  • {Removable Drive}:\{Folder Name}.lnk

Step 6

Search and delete AUTORUN.INF files created by WORM_DORKBOT.MB that contain these strings

[ Learn More ]
[AutoRun]
{GARBAGE_CHARACTERS}
shellexecute=RECYCLER\{Random File Name}.exe
{GARBAGE_CHARACTERS}
icon=shell32.dll,7
{GARBAGE_CHARACTERS}
shell\open\command=RECYCLER\{Random File Name}.exe
{GARBAGE_CHARACTERS}
action=Open folder to view files
{GARBAGE_CHARACTERS}
shell\explore\command=RECYCLER\{Random File Name}.exe
{GARBAGE_CHARACTERS}
useautoplay=1

Step 7

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