VBS.Sorry.C

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Discovered: November 29, 2000
Updated: February 13, 2007 11:52:46 AM
Also Known As: Mcon, TTFLoader, VBS.Fonts
Type: Worm


VBS.Sorry.C is a variant of VBS.Sorry.A. It is a Visual Basic Script worm that copies itself to several folders on a computer hard drive and on network drives. The worm also drops an mIRC configuration file that searches for computers infected with the SubSeven Trojan. It then copies itself and executes on computers that it finds are infected with the SubSeven Trojan.

Previous definitions detected this as VBS.Fonts.



Configure Windows for maximum protection
Because this virus spreads by using shared folders on networked computers, to ensure that the virus does not reinfect the computer after it has been removed, Symantec suggests sharing with read-only access or using password protection. For instructions on how to do this, see your Windows documentation or the document How to configure shared Windows folders for maximum network protection .



Antivirus Protection Dates

  • Initial Rapid Release version December 04, 2000
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version December 04, 2000
  • Latest Daily Certified version September 28, 2010 revision 036

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

Writeup By: Brian Ewell

Discovered: November 29, 2000
Updated: February 13, 2007 11:52:46 AM
Also Known As: Mcon, TTFLoader, VBS.Fonts
Type: Worm


This worm is a Visual Basic Script worm. This worm is identical in functionality to VBS.Sorry.A except for the activity described in step 9.

This worm does the following when it is executed:

  1. It tries to determine if a computer is already infected. If the worm finds multiple copies of itself on the computer, it deletes the extra copies. The worm then deletes the following files, which are common names of other well-known viruses:
    • Network.vbs
    • Msfg.vbs
    • Winsock.vbs
    • A24.vbs
    • Mscfg.exe
    • Ashield.pif
    • Netstat.pif
  2. The virus copies itself to C:\Windows\Fonts\Ttfloader.vbs. If the worm is not running from the Startup folder, or if it is not named Ttfloader.vbs, it deletes itself, displays the following message, and exits:


  3. The worm then attempts to execute Ttfloader.vbs from the \Windows\Fonts folder and makes the following changes to the Windows registry:
    • To the key:

      HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

      it adds the value:

      tfload = wscript.exe windows\fonts\ttfloader.vbs
    • To the key:

      HKEY_CURRENT_USER\Software\Microsoft\Windows Script Host\Settings

      it adds the value:

      Timeout = 0
    • In the key:

      HKEY_LOCAL_MACHINE\Software\Microsoft\Internet Explorer\Main

      it adds or changes the value to:

      Start Page = http://www.zonelabs.com/

      (This enables the virus to start on reboot, never time out when making network connections, and changes the Internet Explorer start page.)
  4. The worm begins to find locations to which it can copy itself. The worm enumerates all drives (including mapped drives).
    • If the drive is a hard drive or a RAM drive, the worm checks for mIRC folders, where it creates a viral Script.ini file and then copies itself to the \Windows\Fonts folder as Sndload.vbs.
    • If the worm finds folders where the name matches anything in the following list, it copies itself to that folder using a randomly selected file name. (The random file name is generated from the Recent Documents list.)
      • pub
      • ftproot
      • wwwroot
      • my
      • download
      • upload
      • share
      • game
      • warez
    • Spaces are appended to the base file name and the extension .vbs is added. For example, if Readme.txt is in the Recent Documents list, the worm will use the file name: Readme.txt .vbs.
    • If the worm finds folders that match the following names, it will delete those folders:
      • chode
      • foreskin
      • d_ckhair
    • If the drive is a removable drive (including floppy drives) or a network drive, the worm copies itself to the drive using the same random file name algorithm. The worm also searches for folders matching Drive:\*win*\StartUp and copies itself as Sndload.vbs. This is generally the Windows StartUp folder. The worm copies itself to folders matching the strings in the following list using a random file name as it did earlier :
      • share
      • download
      • downloads
  5. The worm begins searching for open shares on specific subnets. The worm creates a temporary file with randomly generated IP addresses targeting some subnets more than others. The worm will randomly choose a subnet from one of the following groups:
    • 24.*.*.*
    • 172.128.*.*
    • 152.163-175.*.*
    • 205.163.*.*
    • 4.30-45.*.*
    • 151.196-206.*.*
    • 63.194-207.*.*
    • 216.76-79.*.*
    • 3-243.*.*
  6. The worm pings each IP address and determines if there is a reply.
  7. The worm obtains all the open shares on the computer and maps the network share. It then searches for folders matching Drive:\*win*\Startup and copies itself as Sndload.vbs. If the worm finds any of the folders in the following list, it copies itself as a random file name using the Recent documents list and appending the .vbs extension.
    • share
    • download
    • downloads
  8. The worm removes the network drive.
  9. Each time the worm copies itself to another computer, it adds the line "HOST FOUND!" to the \Windows\System\Ttfload.dll file.

If the computer is infected with the additional mIRC component, the worm will search for computers infected with the SubSeven trojan, where it will upload and execute itself.

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: Brian Ewell

Discovered: November 29, 2000
Updated: February 13, 2007 11:52:46 AM
Also Known As: Mcon, TTFLoader, VBS.Fonts
Type: Worm


To repair damage done by the worm, you need to complete the following tasks:

  • Delete all files that Norton AntiVirus (NAV) detects as infected by VBS.Sorry.C.
  • Restore the Internet Explorer Start Page if desired.
  • Delete the registry entries made by the worm.

Please refer to the appropriate sections for instructions on complete each task.

To delete the infected files:
  1. Run LiveUpdate to make sure that you have the most recent virus definitions.
  2. Start NAV and run a full system scan. Unless you are using NAV 2001, make sure that NAV is set to scan all files.
  3. Delete any files that are detected as infected with VBS.Sorry.C.

To restore the Internet Explorer Start Page:
  1. Start Internet Explorer, and go the Web page that you want to set as your home page.
  2. Click Tools, and then click Internet Options.
  3. In the Home page section of the General tab, click "Use Current."

To remove the registry entries made by the worm:

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.
  1. Click Start, and then click Run. The Run dialog box appears.
  2. Type regedit and then click OK. The Registry Editor opens.
  3. Browse to and select the following subkey:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
  4. In the right pane, locate and delete the following value:

    tfload = wscript.exe windows\fonts\ttfloader.vbs
  5. Browse to and select the following subkey:

    HKEY_CURRENT_USER\Software\Microsoft\Windows Script Host\Settings
  6. In the right pane, locate and delete the following value:

    Timeout = 0
  7. Close the Registry Editor.


Writeup By: Brian Ewell