ALIASES:

Worm:Win32/Dorkbot (Microsoft); BackDoor-FCQS!9F6E872F2C65 (McAfee); Trojan.Cryptdef!gen13 (Symantec); Worm.Win32.Ngrbot.apes (Kaspersky); Mal/Wonton-BB (Sophos); Trojan.Win32.Generic!BT (Sunbelt); Trojan horse BackDoor.SmallX.BTJ (AVG)

 PLATFORM:

Windows

 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 itself after execution.

  TECHNICAL DETAILS

File Size: 213,504 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 06 Jun 2015

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%\WindowsUpdate\Updater.exe
  • %User Profile%\Application Data\c731200
  • %User Profile%\Update\Explorer.exe
  • %User Profile%\Update\Update.exe
  • %User Profile%\themes\Asrara.exe

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

It creates the following folders:

  • %User Profile%\Application Data\WindowsUpdate
  • %User Profile%\Application Data\Update

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} 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 Update Installer = "%User Profile%\WindowsUpdate\Updater.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Taskman = "%User Profile%\WindowsUpdate\Updater.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Asrara = "%User Profile%\themes\Asrara.exe"

Other System Modifications

This worm deletes the following files:

  • %User Profile%\Update\Explorer.exe
  • %User Profile%\Update\Update.exe
  • %User Startup%\desktop.ini
  • %Common Startup%\desktop.ini
  • %User Profile%\Application Data\ScreenSaverPro.scr
  • %User Profile%\Application Data\temp.bin

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.. %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.. %Common Startup% is the system's shared Startup folder, which is usually C:\Documents and Settings\All Users\Start Menu\Programs\Startup on Windows 2000, XP, and Server 2003.)

Dropping Routine

This worm drops the following files:

  • %User Profile%\Application Data\c731200

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

Other Details

This worm connects to the following possibly malicious URL:

  • http://api.{BLOCKED}ia.com
  • {BLOCKED}.168.196

It deletes itself after execution.

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine: 9.750

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

Identify and delete files detected as WORM_DORKBOT.MNG using either the Startup Disk or Recovery Console

[ 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
    • Windows Update Installer = "%User Profile%\WindowsUpdate\Updater.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • Taskman = "%User Profile%\WindowsUpdate\Updater.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Asrara = "%User Profile%\themes\Asrara.exe"

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.
  • %User Profile%\Application Data\c731200

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.
  • %User Profile%\Application Data\WindowsUpdate
  • %User Profile%\Application Data\Update

Step 6

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

Step 7

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • %User Profile%\Update\Explorer.exe
  • %User Profile%\Update\Update.exe
  • %User Startup%\desktop.ini
  • %Common Startup%\desktop.ini
  • %User Profile%\Application Data\ScreenSaverPro.scr
  • %User Profile%\Application Data\temp.bin


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