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09 September 2002
13 February 2007
Also Known As:
Systems Affected:

VBS.Lavra.B.Worm is a Trojan horse that is written in Microsoft Visual Basic Script. It attempts to delete antivirus and personal firewall software. In an attempt to spread, it copies itself as numerous files to the shared folders of several file-sharing programs.

NOTE: Definitions dated prior to September 12, 2002 may detect this as VBS.Thambl.

Antivirus Protection Dates

  • Initial Rapid Release version 09 September 2002
  • Latest Rapid Release version 28 September 2010 revision 054
  • Initial Daily Certified version 09 September 2002
  • Latest Daily Certified version 28 September 2010 revision 036
  • Initial Weekly Certified release date 11 September 2002
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

When VBS.Lavra.B.Worm runs, it does the following:

It copies itself as:
  • C:\Windows\Lbamht.vbs
  • C:\WinNT\Lbamht.vbs

It attempts to delete the following files:
  • C:\AntiViral Toolkit Pro\*.*
  • C:\Program Files\Command Software\F-PROT95\*.*
  • C:\Program Files\McAfee\VirusScan\*.*
  • C:\Program Files\Norton AntiVirus\*.*
  • C:\Toolkit\FindVirus\*.*
  • C:\Program Files\Panda Software\Panda Antivirus Titanium\*.*
  • C:\PC-Cillin 95\*.*
  • C:\PC-Cillin 97\*.*
  • C:\Program Files\Trend Micro\PC-cillin 2002\*.*
  • C:\Program Files\Zone Labs\ZoneAlarm\*.*
  • C:\Program Files\Tiny Personal Firewall\*.*

It then copies itself as numerous files into the shared folders of these peer-to-peer file-sharing programs:
  • C:\Program Files\Grokster\My Grokster\CristinaAguilera.Jpg.vbs
  • C:\Program Files\Grokster\My Grokster\AVP-Spanish Patch.Zip.VBS
  • C:\Program Files\Grokster\My Grokster\Norton Antivirus 2002 Crack.Zip.vbs
  • C:\Program Files\Grokster\My Grokster\SilviaSaintDoubleAnalAction.jpg.vbs
  • C:\Program Files\Grokster\My Grokster\Panda Titanium
  • C:\Program Files\Grokster\My Grokster\LasKetChupXXX.jpg.vbs
  • C:\ARCHIV~1\Grokster\My Grokster\CristinaAguilera.Jpg.vbs
  • C:\ARCHIV~1\Grokster\My Grokster\AVP-Spanish Patch.Zip.VBS
  • C:\ARCHIV~1\Grokster\My Grokster\Norton Antivirus 2002 Crack.Zip.vbs
  • C:\ARCHIV~1\Grokster\My Grokster\SilviaSaintDoubleAnalAction.jpg.vbs
  • C:\ARCHIV~1\Grokster\My Grokster\Panda Titanium
  • C:\ARCHIV~1\Grokster\My Grokster\LasKetChupXXX.jpg.vbs

  • C:\Program Files\Morpheus\My Shared Folder\CristinaAguilera.Jpg.vbs
  • C:\Program Files\Morpheus\My Shared Folder\AVP-Spanish Patch.Zip.VBS
  • C:\Program Files\Morpheus\My Shared Folder\Norton Antivirus 2002 Crack.Zip.vbs
  • C:\Program Files\Morpheus\My Shared Folder\SilviaSaintDoubleAnalAction.jpg.vbs
  • C:\Program Files\Morpheus\My Shared Folder\Panda Titanium
  • C:\Program Files\Morpheus\My Shared Folder\LasKetChupXXX.jpg.vbs
  • C:\archiv~1\Morpheus\My Shared Folder\CristinaAguilera.Jpg.vbs
  • C:\archiv~1\Morpheus\My Shared Folder\AVP-Spanish Patch.Zip.VBS
  • C:\archiv~1\Morpheus\My Shared Folder\Norton Antivirus 2002 Crack.Zip.vbs
  • C:\archiv~1\Morpheus\My Shared Folder\SilviaSaintDoubleAnalAction.jpg.vbs
  • C:\archiv~1\Morpheus\My Shared Folder\Panda Titanium
  • C:\archiv~1\Morpheus\My Shared Folder\LasKetChupXXX.jpg.vbs

  • C:\Program Files\ICQ\shared files\CristinaAguilera.Jpg.vbs
  • C:\Program Files\ICQ\shared files\AVP-Spanish Patch.Zip.VBS
  • C:\Program Files\ICQ\shared files\Norton Antivirus 2002 Crack.Zip.vbs
  • C:\Program Files\ICQ\shared files\SilviaSaintDoubleAnalAction.jpg.vbs
  • C:\Program Files\ICQ\shared files\Panda Titanium
  • C:\Program Files\ICQ\shared files\LasKetChupXXX.jpg.vbs
  • C:\archiv~1\ICQ\shared files\CristinaAguilera.Jpg.vbs
  • C:\archiv~1\ICQ\shared files\AVP-Spanish Patch.Zip.VBS
  • C:\archiv~1\ICQ\shared files\Norton Antivirus 2002 Crack.Zip.vbs
  • C:\archiv~1\ICQ\shared files\SilviaSaintDoubleAnalAction.jpg.vbs
  • C:\archiv~1\ICQ\shared files\Panda Titanium
  • C:\archiv~1\ICQ\shared files\LasKetChupXXX.jpg.vbs

  • C:\Program Files\Bearshare\Shared\CristinaAguilera.Jpg.vbs
  • C:\Program Files\Bearshare\Shared\AVP-Spanish Patch.Zip.VBS
  • C:\Program Files\Bearshare\Shared\Norton Antivirus 2002 Crack.Zip.vbs
  • C:\Program Files\Bearshare\Shared\SilviaSaintDoubleAnalAction.jpg.vbs
  • C:\Program Files\Bearshare\Shared\Panda Titanium
  • C:\Program Files\Bearshare\Shared\LasKetChupXXX.jpg.vbs
  • C:\archiv~1\Bearshare\Shared\CristinaAguilera.Jpg.vbs
  • C:\archiv~1\Bearshare\Shared\AVP-Spanish Patch.Zip.VBS
  • C:\archiv~1\Bearshare\Shared\Norton Antivirus 2002 Crack.Zip.vbs
  • C:\archiv~1\Bearshare\Shared\SilviaSaintDoubleAnalAction.jpg.vbs
  • C:\archiv~1\Bearshare\Shared\Panda Titanium
  • C:\archiv~1\Bearshare\Shared\LasKetChupXXX.jpg.vbs

  • C:\Program Files\KaZaA\My Shared Folder\CristinaAguilera.Jpg.vbs
  • C:\Program Files\KaZaA\My Shared Folder\AVP-Spanish Patch.Zip.VBS
  • C:\Program Files\KaZaA\My Shared Folder\Norton Antivirus 2002 Crack.Zip.vbs
  • C:\Program Files\KaZaA\My Shared Folder\SilviaSaintDoubleAnalAction.jpg.vbs
  • C:\Program Files\KaZaA\My Shared Folder\Panda Titanium
  • C:\Program Files\KaZaA\My Shared Folder\LasKetChupXXX.jpg.vbs
  • C:\ARCHIV~1\KaZaA\My Shared Folder\CristinaAguilera.Jpg.vbs
  • C:\ARCHIV~1\KaZaA\My Shared Folder\AVP-Spanish Patch.Zip.VBS
  • C:\ARCHIV~1\KaZaA\My Shared Folder\Norton Antivirus 2002 Crack.Zip.vbs
  • C:\ARCHIV~1\KaZaA\My Shared Folder\SilviaSaintDoubleAnalAction.jpg.vbs
  • C:\ARCHIV~1\KaZaA\My Shared Folder\Panda Titanium
  • C:\ARCHIV~1\KaZaA\My Shared Folder\LasKetChupXXX.jpg.vbs

The Trojan adds the values

LARVA    C:\windows\lbamht.vbs
LARVAx   C:\winnt\lbamht.vbs

to the registry key


so that it runs each time that you start Windows.

On Windows 95/98/Me only, the Trojan adds the lines

@Start C:\Windows\lbamht.vbs>null
@Start C:\Winnt\lbamht.vbs>null

to the C:\Autoexec.bat file so that the Trojan runs when you start Windows.


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.

  • These instructions are for all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.
  • If the Trojan was successful in deleting Norton AntiVirus, reinstall that program before you can continue with the removal procedure.
  1. Update the virus definitions.
  2. Run a full system scan, and delete all files that are detected as VBS.Lavra.B.Worm.
  3. Delete the values

    LARVA    C:\windows\lbamht.vbs
    LARVAx   C:\winnt\lbamht.vbs

    that the Trojan added to the registry key

  4. (Windows 95/98/Me only) Delete the lines

    @Start C:\Windows\lbamht.vbs>null
    @Start C:\Winnt\lbamht.vbs>null

    that the Trojan added to the C:\Autoexec.bat file.
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.Lavra.B.Worm, click Delete.

To delete the values that the Trojan added 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 these values:

    LARVA    C:\windows\lbamht.vbs
    LARVAx   C:\winnt\lbamht.vbs
  5. Exit the Registry Editor.

To delete the lines that the Trojan added to the Autoexec.bat file:
This is necessary only on Windows 95/98/Me-based computers.

NOTE: (For Windows Me users only) Due to the file-protection process in Windows Me, a backup copy of the file that you are about to edit exists in the C:\Windows\Recent folder. Symantec recommends that you delete this file before you continue with the steps in this section. To do this using Windows Explorer, go to C:\Windows\Recent, and in the right pane select the Win.ini file and delete it. It will be regenerated as a copy of the file that you are about to edit when you save your changes to that file.
  1. Click Start, and click Run.
  2. Type the following, and then click OK.

    edit c:\autoexec.bat

    The MS-DOS Editor opens.
  3. Look for these two lines:

    @Start C:\Windows\lbamht.vbs>null
    @Start C:\Winnt\lbamht.vbs>null
  4. If one or both exist, then for each one select the entire line. Be sure that you have not selected any other text, and then press Delete.
  5. Click File, and click Save.
  6. Click File, and click Exit.

Writeup By: Kaoru Hayashi