Discovered: October 16, 2001
Updated: February 13, 2007 11:37:28 AM
Type: Worm


VBS.Loveletter.CV@mm is a Visual Basic Script (VBS) worm that sends email to all contacts that are in the Microsoft Outlook address book. It copies itself into the \Windows\System folder as Msword.vbs and Thwin.vbs, and deletes up to five files with one of the following extensions: .xls, .doc, .wav, .dwg, .mp3, .bak, .wav, .bmp, .htm, .hlp, .chm, .jpg, .gif, .scr, .ttf, .mid, .cdr, .mdb, .dbf, or .ico. It saves a list of the files that it deleted in the file \Windows\System\ListWin.txt. It also tries to copy itself as A:\Unsch.doc.vbs.

Antivirus Protection Dates

  • Initial Rapid Release version October 16, 2001
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version October 16, 2001
  • 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: Dave Adamczyk

Discovered: October 16, 2001
Updated: February 13, 2007 11:37:28 AM
Type: Worm


When VBS.Loveletter.CV@mm is executed, it performs the following actions:

First it copies itself to the \Windows\System folder as:

  • Msword.vbs
  • Thwin.vbs
  • The original file name that you received as an email attachment.

    NOTE: This file name will vary. In one submission that was received by Symantec Security Response, the file name was "Hotmail - Carpeta Bandeja de entrada.htm.vbs"

Next it sends itself to all addresses in the Microsoft Outlook address book. The message has the following characteristics:

Subject: <The original file name that you received as an email attachment, minus the last 7 characters>
Message:   <Recipient name> Eres algo especial...escríbeme  (English translation: You are something special... Write to me)

Attachment: <the original file name>

Next, it creates the value

THWIN  C:\WINDOWS\SYSTEM\THWIN.vbs

in the registry key

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

which causes the worm to run when you start Windows.

It then displays the following message:

ERROR
Error de lectura. No se puede abrir el archivo.

English translation: Read error. Cannot open file.

Next it randomly chooses one of the following file extensions: .xls, .doc, .wav, .dwg, .mp3, .bak, .wav, .bmp, .htm, .hlp, .chm, .jpg, .gif, .scr, .ttf, .mid, .cdr, .mdb, .dbf, or .ico. It then deletes the first five files with that extension that it finds.

The second time that the worm runs, it waits 10 minutes and then attempts to copy itself as Msword.vbs to drive A if a floppy disk is loaded in the drive.

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: Dave Adamczyk

Discovered: October 16, 2001
Updated: February 13, 2007 11:37:28 AM
Type: Worm


To remove this worm, delete files detected as VBS.Loveletter.CV@mm, examine the ListWin.txt to find the names of the files deleted by the worm, and remove the value that the worm added to the registry /Run key.

To delete VBS.Loveletter.CV@mm:

  1. Run LiveUpdate to make sure that you have the most recent virus definitions.
  2. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files. For instructions on how to do this, read the document How to configure Norton AntiVirus to scan all files.
  3. Run a full system scan.
  4. Delete all files that are detected as VBS.Loveletter.CV@mm.

To examine the ListWin.txt. file:
This file contains a list of the files that the worm deleted.
  1. Using Windows Explorer, locate and double-click the \Windows\System\ListWin.txt file.
  2. If any of the files in the list are files that you need, replace then from clean backup copies.
  3. (Optional) Delete the ListWin.txt file if you want.

To edit the registry:

CAUTION : We strongly recommend that you back up the system registry before you make any changes. Incorrect changes to the registry could result in permanent data loss or corrupted files. Please make sure that you modify only the keys that are specified. Please see the document How to back up the Windows registry before you proceed.
  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 following key:

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

    THWIN  C:\WINDOWS\SYSTEM\THWIN.vbs
  5. Click Registry, and click Exit.


Writeup By: Dave Adamczyk