Analysis by: Rika Joi Gregorio
ALIASES:

Trojan.Win32.Jorik.Nrgbot.bvf(Kaspersky), a variant of Win32/Injector.VZA trojan(Eset), W32/Injector.WXP!tr(Fortinet)

 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.

  TECHNICAL DETAILS

File Size: 183,808 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 22 May 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%\Windows\winlogon.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.)

It drops the following files:

  • {Drive Letter}:\RECYCLER\desktop.ini

It drops and executes the following files:

  • %User Temp%\{random}.bat - will be deleted afterwards

(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 the following copies of itself into the affected system:

  • %Application Data%\{random file name}.exe - (for Windows Vista and 7)

(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 creates the following folders:

  • %Application Data%\Windows

(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
Windows Defender = "%Application Data%\Windows\winlogon.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random file name} = "%Application Data%\{random file name}.exe" (for Windows Vista and 7)

Other System Modifications

This worm adds the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
Visual Basic

HKEY_CURRENT_USER\Software\Microsoft\
Visual Basic\6.0

Propagation

This worm creates the following folders in all removable drives:

  • {Drive Letter}:\RECYCLER

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

  • {Drive Letter}:\RECYCLER\{random}.exe

Other Details

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

  • api.wipmania.com

NOTES:

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: 9.946.07
FIRST VSAPI PATTERN DATE: 28 May 2013
VSAPI OPR PATTERN File: 9.947.00
VSAPI OPR PATTERN Date: 29 May 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 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.

 
  • In HKEY_CURRENT_USER\Software\Microsoft
    • Visual Basic

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Windows Defender = "%Application Data%\Windows\winlogon.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {random file name} = "%Application Data%\{random file name}.exe"

Step 5

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.
  • %Application Data%\Windows
  • {Drive Letter}:\RECYCLER

Step 6

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}:\RECYCLER\desktop.ini

Step 7

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