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WORM_DORKBOT.EF

October 09, 2012
 Analysis by: Kathleen Notario
 ALIASES:

Worm:Win32/Dorkbot.gen!A (Microsoft); W32.IRCBot (Symantec); Backdoor.Tofsee.DN (Fsecure); Worm.Win32.Ngrbot.auo (Kaspersky)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • 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:

126,976 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

26 Aug 2011

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:

  • %User Profile%\Application Data\Fhwuwz.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
Fhwuwz = "%User Profile%\Application Data\Fhwuwz.exe"

Other Details

This worm connects to the following possibly malicious URL:

  • ng.{BLOCKED}allone.com
  • ng.{BLOCKED}ketbaby.com
  • ng.{BLOCKED}opperz11.com
  • ng.{BLOCKED}ousez11.com
  • ng.{BLOCKED}oan.com

It deletes the initially executed copy of itself

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

8.826.02

FIRST VSAPI PATTERN DATE:

09 Mar 2012

VSAPI OPR PATTERN File:

8.827.00

VSAPI OPR PATTERN Date:

10 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

Identify and terminate files detected as WORM_DORKBOT.EF

[ Learn More ]
  1. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  2. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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
    • Fhwuwz = "%User Profile%\Application Data\Fhwuwz.exe"

Step 4

Scan your computer with your Trend Micro product to delete files detected as WORM_DORKBOT.EF. 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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