VBS.Lunnet.A

Printer Friendly Page

Discovered: March 06, 2003
Updated: February 13, 2007 11:43:51 AM
Type: Worm
Systems Affected: Windows


VBS.Lunnet.A is a Visual Basic Script worm that attempts to spread using the KaZaA and Grokster file-sharing networks. The worm also attempts a Denial of Service attack on www.ytunnel.digitalcitrus.com.

VBS.Lunnet.A adds a command to the Autoexec.bat file to format the hard drive the next time you start the computer.

Antivirus Protection Dates

  • Initial Rapid Release version March 06, 2003
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version March 06, 2003
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date March 12, 2003

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Writeup By: Eric Chien

Discovered: March 06, 2003
Updated: February 13, 2007 11:43:51 AM
Type: Worm
Systems Affected: Windows


When VBS.Lunnet.A is executed, it does the following:

  1. Copies itself to:
    • C:\Program Files\Kazaa\My Shared Folder\Ytunnel Pro Crack.exe.vbs
    • C:\Program Files\KaZaA Lite\My Shared Folder\Ytunnel Pro Crack.exe.vbs
    • C:\Program Files\Grokster\My Grokster\Ytunnel Pro Crack.exe.vbs

      NOTE: These folders are the default sharing folders for KaZaA and Grokster.

  2. Searches for the following folders:
    • C:\Program Files\Y!Tunnel
    • C:\Program Files\Y!Tunnel SP1
    • C:\Program Files\Y!Tunnel SP2

      If any of these folders exist, the worm does the following:
      • Attempts a Denial of Service attack by sending repeated ping packets to www.ytunnel.digitalcircus.com.
      • Adds the line:

        Echo y | Format C:

        to the C:\Autoexec.bat file. This command will format the C drive of your Windows 95/98/Me computer the next time you start the computer.

Recommendations

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.

Writeup By: Eric Chien

Discovered: March 06, 2003
Updated: February 13, 2007 11:43:51 AM
Type: Worm
Systems Affected: Windows


The following instructions pertain to 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 the files detected as VBS.Lunnet.A.
  3. Delete the line that was added to the Autoexec.bat file (Windows 95/98/Me only).

For specific details on each of these steps, read the following instructions.

1. Updating the virus definitions
Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:
  • Running LiveUpdate, which is the easiest way to obtain the virus definitions: These virus definitions are posted to the LiveUpdate servers once each week (usually on Wednesdays), unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, refer to the Virus Definitions (LiveUpdate), in the "Protection" section, at the top of this writeup.
  • Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). You should download the definitions from the Symantec Security Response Web site and manually install them. To determine whether definitions for this threat are available by the Intelligent Updater, refer to the Virus Definitions (Intelligent Updater), in the "Protection" section, at the top of this writeup.

    The 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.

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


3. Delete the line that was added to the Autoexec.bat file
If you are running Windows 95/98/Me, follow these steps:
  1. The function you perform depends on your operating system:
    • Windows 95/98: Go to step b.
    • Windows Me: If you are running Windows Me, the Windows Me file-protection process may have made a backup copy of the Autoexec.bat file that you need to edit. If this backup copy exists, it will be in the C:\Windows\Recent folder. Symantec recommends that you delete this file before continuing with the steps in this section. To do this:
      • Start Windows Explorer.
      • Browse to and select the C:\Windows\Recent folder.
      • In the right pane, select the Autoexec.batfile and delete it. The Autoexec.bat file will be regenerated when you save your changes to it in step f.
  2. Click Start, and then click Run.
  3. Type the following:

    edit c:autoexec.bat

    And then click OK. (The MS-DOS Editor opens.)

    NOTE: If Windows is installed in a different location, make the appropriate path substitution.
  4. Look for a line similar to:

    Echo y | Format C:
  5. If this line exists, delete it.
  6. Click File, and then click Save.
  7. Click File, and then click Exit.


Writeup By: Eric Chien