Analysis by: Sabrina Lei Sioting
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Propagates via removable drives, Via physical/removable drives, Dropped by other malware

This worm arrives via removable drives. It may be dropped by other malware.

It also has rootkit capabilities, which enables it to hide its processes and files from the user.

  TECHNICAL DETAILS

File Size: 118,282 bytes
Memory Resident: Yes
Initial Samples Received Date: 06 Mar 2012
Payload: Hides files and processes, Connects to URLs/IPs

Arrival Details

This worm arrives via removable drives.

It may be dropped by other malware.

Installation

This worm drops the following copies of itself into the affected system:

  • %User Profile%\Application Data\{random characters}.exe

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)

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
{malware file name} = "%User Profile%\Application Data\{malware file name}.exe"

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 characters}.exe

Rootkit Capabilities

This worm also has rootkit capabilities, which enables it to hide its processes and files from the user.

Other Details

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

  • http://api.{BLOCKED}ania.com/

NOTES:

This worm 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: 9.200
FIRST VSAPI PATTERN FILE: 8.820.03
FIRST VSAPI PATTERN DATE: 06 Mar 2012
VSAPI OPR PATTERN File: 8.821.00
VSAPI OPR PATTERN Date: 07 Mar 2012

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Scan your computer with your Trend Micro product and note files detected as WORM_DORKBOT.FU

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

Delete the registry entry with an unknown data 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
    • {malware file name} = "%User Profile%\Application Data\{malware file name}.exe"

Step 5

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. {drive letter}:\RECYCLER

Step 6

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