Threat Explorer

The Threat Explorer is a comprehensive resource consumers can turn to for daily, accurate, up-to-date information on the latest threats, risks and vulnerabilities.



13 September 2002
13 February 2007
Also Known As:
VBS_NEDAL.A [Trend], VBS/Amalad.a [McAfee], VBS/Nedal-A [Sophos], VBS.VBSWG.AS [CA], VBS/Nedal [Panda], I-Worm.Melhack [AVP]
Systems Affected:

VBS.Melhack.B is an intended mass mailing worm that is written in Visual Basic. It copies itself as OsamaLaden.vbs into two locations.

The virus contains bugs that keep it from performing most of the intended actions. One such intended action is to send email messages to all contacts in the Microsoft Outlook Address Book.

Antivirus Protection Dates

  • Initial Rapid Release version 16 September 2002
  • Latest Rapid Release version 20 August 2008 revision 017
  • Initial Daily Certified version 16 September 2002
  • Latest Daily Certified version 20 August 2008 revision 016
  • Initial Weekly Certified release date 18 September 2002
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

When VBS.Melhack.B runs, it performs these actions:

It copies itself to:
  • %system%\OsamaLaden.vbs
  • %windir%\OsamaLaden.vbs

  • %windir% is a variable. The worm locates the Windows installation folder (by default this is C:\Windows or C:\Winnt) and copies itself to that location.
  • %system% is a variable. The worm locates the System folder and copies itself to that location. By default this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).

It changes the registered Windows user to OsamaBinLaden by changing the value

RegisteredOwner OsamaBinLaden

in the registry key


It adds the values

OsamaBinLaden wscript.exe %system%\OsamaLaden.vbs %
OsamaLaden C:\OsamaLaden.bat

to the registry key


so that the virus starts when you start Windows.

The virus contains bugs that keep it from performing most of the actions that it intended. One such intended action is to send email messages to all contacts in the Microsoft Outlook Address Book; the message has the following characteristics:

Subject:  Osama Bin Laden Comes Back!
Attachment: There is no attachment. The virus is contained within the HTML body of the email message.

Another intended action is to overwrite (with the virus) files that have one of the following extensions:
  • .vbs
  • .vbe
  • .gif
  • .bmp
  • .avi
  • .mp3
  • .mpg
  • .zip
  • .cab
  • .mdb
  • .xls
  • .lnk
  • .doc
  • .txt
  • .rtf


Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.

NOTE: These instructions are for all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.
  1. Update the virus definitions.
  2. Run a full system scan, and delete all files that are detected as VBS.Melhack.B.
  3. Reverse the changes that the virus made to the Windows registry.
For details on how to do this, read the following instructions.

To update the virus definitions:
All virus definitions receive full quality assurance testing by Symantec Security Response before being posted to our servers. There are two ways to obtain the most recent virus definitions:
  • Run LiveUpdate, which is the easiest way to obtain virus definitions. These virus definitions are posted to the LiveUpdate servers one time each week (usually Wednesdays) unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, look at the Virus Definitions (LiveUpdate) line at the top of this write-up.
  • Download the definitions using the Intelligent Updater. Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). They must be downloaded from the Symantec Security Response Web site and installed manually. To determine whether definitions for this threat are available by the Intelligent Updater, look at the Virus Definitions (Intelligent Updater) line at the top of this write-up.

    Intelligent Updater virus definitions are available here. For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, click here.

To scan for and delete the infected files:
  1. Start your Symantec antivirus program, and make sure that it is configured to scan all files.
  2. Run a full system scan.
  3. If any files are detected as infected with VBS.Melhack.B, click Delete.

To reverse the changes that the virus made to the registry:

CAUTION : Symantec strongly recommends that you back up the registry before you make any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify only the keys that are specified. Read the document How to make a backup of the Windows registry for instructions.
  1. Click Start, and click Run. The Run dialog box appears.
  2. Type regedit and then click OK. The Registry Editor opens.
  3. Navigate to the key

  4. In the right pane, delete the values:

    OsamaBinLaden wscript.exe %system%\OsamaLaden.vbs %
    OsamaLaden C:\OsamaLaden.bat
  5. Navigate to the key

  6. In the right pane, double-click

    RegisteredOwner OsamaBinLaden
  7. Change the text to specify the registered owner of the operating system, and then click OK.
  8. Exit the Registry Editor.

Writeup By: Douglas Knowles