Threat Explorer

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VBS.Tune.B

VBS.Tune.B

Discovered:
29 September 2000
Updated:
13 February 2007

VBS.Tune.B is a worm written in the Visual Basic Scripting language. It is a variant of VBS.Tune that spreads using Microsoft Outlook, mIRC, Pirch9x, and mapped drives.

This worm creates six copies of itself and modifies System.ini, Win.ini, and the Windows registry.

Antivirus Protection Dates

  • Initial Rapid Release version 03 October 2000
  • Latest Rapid Release version 28 September 2010 revision 054
  • Initial Daily Certified version 03 October 2000
  • Latest Daily Certified version 28 September 2010 revision 036
  • Initial Weekly Certified release date pending
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

VBS.Tune.B creates six copies of itself when executed and modifies the Windows registry, System.ini, and Win.ini. The worm creates entries in these locations that execute one of the copies when Microsoft Windows is started. The inserted files are as follows:
  • C:\Windows\System\VideobsGirl.vbs
  • C:\Windows\Iosys.vbs
  • [Tempfolder]\~df48e3tmp.vbs
  • C:\Windows\System\Kernel.oxc
  • C:\Windows\Winsck.vbs
  • C:\Windows\System\Explorer.oxc

When these files are inserted, the worm changes another registry key. This key creates/changes the file association for .oxc files to be executed as VB scripts.
The worm first attempts to spread across mapped drives by checking the status of all drive letters between C and Z. If the status is mapped or fixed, the worm copies itself to the root of the drive as Logosys.vbs.

The worm also includes an sprd function that contains the email routine. The sprd function emails the worm to everyone in the Microsoft Outlook address book. It then sets a registry key to prevent the email routine from being triggered more than once. The body of the message reads as follows:

Hey, you really need to check out this attached file I sent you...please check it out as soon as possible

The worm checks to see if mIRC or Pirch9x is installed on the computer. If either of them is found, the worm creates a script that spreads via IRC (Internet Relay Chat). mIRC must be installed in the default path, or the worm is unable to find it.

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.

To repair damage done by VBS.Tune:
  • Run a full system scan, and delete any infected files. Do a full shutdown of the computer, and then restart.
  • Delete any values that are loading from the registry's \Run key that refer to Tune.vbs.
  • Remove references to Tune.vbs from the Run= and Load= lines of the Win.ini file.
  • Remove references to Tune.vbs from the Shell= line of the System.ini file.

For detailed instructions on how to do this, see the sections that follow.

NOTE: The procedure described in this document is somewhat complex. We assume that you are familiar with basic Windows and DOS procedures. If you are not, then we suggest that you obtain the services of a qualified computer consultant.

Run a full system scan
After making sure that you have current virus definitions, run a full system scan. Make sure that Norton AntiVirus is set to scan all files. Delete any files that are found to be infected.

When the scan has finished, exit all programs, shut down the computer, and then turn off the power. Leave the computer off for at least thirty seconds. This is necessary to clear memory. Do not use the reset button or perform a normal restart from Windows.

NOTE: You will likely see error messages when Windows restarts. Click OK or Ignore as needed.

Edit the registry
You must remove the values that were added to the Windows registry by the worm. Follow these steps to do this:

CAUTION : We strongly recommend that you back up the system registry before making any changes to it. Incorrect changes to the registry may result in permanent data loss or corrupted files. Be sure to modify the specified keys only. See the document How to back up the Windows registry before proceeding.

To edit the registry:
  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 and select the following subkey:

    HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
  4. In the right pane, look for any values that refer to Tune.vbs. These may have Tune.vbs as part of the value, or they may be displayed as one or both of the following:

    \ScanRegistry
    \TaskMonitor
  5. If you find any of these, then select them, press Delete, and click Yes to confirm the deletion.
  6. Navigate to and select the following subkey:

    HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunServoces
  7. In the right pane, look for any values that refer to Tune.vbs. These may have Tune.vbs as part of the value, or they may be displayed as one or both of the following:

    \ScanRegistry
    \TaskMonitor
  8. If you find any of these, then select them, press Delete, and click Yes to confirm the deletion.
  9. Click the Registry menu, and click Exit to save the changes and exit the Registry Editor.

To edit system files
This worm also makes changes to two system files. Follow these steps to remove the changes:
  1. Click Start, and click Run.
  2. Type sysedit and then click OK. The System Configuration Editor appears.
  3. Click the Window menu and click C:\WINDOWS\WIN.INI. The Win.ini window is brought to the front.

    NOTE: This menu item may appear slightly different if Windows is installed in a different location.
  4. In the [windows] section at the beginning of the file, look for the following lines:

    load=
    run=
  5. On both lines, look for references to Tune.vbs. If found, carefully delete these references. Make sure that you delete only these references, and not the lines that follow.
  6. Click the Window menu, and then click C:\WINDOWS\SYSTEM.INI. The System.ini window is brought to the front.
  7. In the [boot] section at the beginning of the file, look for the line that begins with:

    shell=Explorer.exe
  8. Look for an additional reference that has been added to it. It may appear similar to the following:

    shell=Explorer.exe Explorer.Vbs
  9. Remove the reference to Explorer.vbs. When you are finished the line must appear as follows:

    shell=Explorer.exe
  10. Click the File menu, and click Save.
  11. Exit the System Configuration Editor.

This completes the removal of the worm. Run another full system scan.

NOTE: If you are using the mIRC, Pirch programs, and you find that these programs no longer operate properly, you will need to either restore the following files from an uninfected backup, or reinstall the software:
  • C:\Mirc\Script.ini
  • C:\Mirc\Mirc.ini
  • C:\Pirch98\Events.ini
  • C:\Pirch98\Pirch98.ini


Writeup By: Neal Hindocha