VBS.Lunnet.A

SUMMARY

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.

Protection

• Virus Definitions (LiveUpdate™ Weekly) March 12, 2003
• Virus Definitions (Intelligent Updater) March 6, 2003

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 0 - 49
• Number of Sites: 0 - 2
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Easy

Damage

• Damage Level: Medium
• Deletes Files: Formats the C: drive
• Degrades Performance: Attempts a Denial of Service attack

Distribution

• Distribution Level: Medium
• Target of Infection: Kazaa and Grokster

TECHNICAL DETAILS

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

1. Copies itself to:
   • C:Program FilesKazaaMy Shared FolderYtunnel Pro Crack.exe.vbs
   • C:Program FilesKaZaA LiteMy Shared FolderYtunnel Pro Crack.exe.vbs
   • C:Program FilesGroksterMy GroksterYtunnel Pro Crack.exe.vbs
     
     NOTE: These folders are the default sharing folders for KaZaA and Grokster.
     
     
2. Searches for the following folders:
   • C:Program FilesY!Tunnel
   • C:Program FilesY!Tunnel SP1
   • C:Program FilesY!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":

• Turn off and remove unneeded services. By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server. These services are avenues of attack. If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates.
• If a blended 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 (for example, all Windows-based computers should have the current Service Pack installed.). Additionally, please apply any security updates that are mentioned in this writeup, in trusted Security Bulletins, or on vendor Web sites.
• 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.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate infected computers quickly to prevent further compromising your organization. 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.

REMOVAL

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.
   • For Norton AntiVirus consumer products: Read the document, "How to configure Norton AntiVirus to scan all files."
   • For Symantec AntiVirus Enterprise products: Read the document, "How to verify that a Symantec Corporate antivirus product is set to scan All 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:WindowsRecent 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:WindowsRecent 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.