Threat Explorer

The Threat Explorer is a comprehensive resource consumers can turn to for daily, accurate, up-to-date information on the latest threats, risks and vulnerabilities.

VBS.Numgame@mm

VBS.Numgame@mm

Discovered:
15 February 2002
Updated:
13 February 2007
Also Known As:
GuessGame, VBS_NUMGAME.A

VBS.Numgame@mm is a VBScript threat that may arrive by email from a known contact. It contains the following information:

Subject: Are you <contact name> my valentine?
Message : Hi <contact name> my valentine, remember me? I ain't seen you in ages! Anyway, check-out and play the attached guess-the-number-game to guess who I am. See you soon, bye-bye!"
Attachment: GuessGame.html (or GuessGame.vbe)

This script contains instructions to modify system settings and delete files. It may also modify the system date to "04-08-1981".

Antivirus Protection Dates

  • Initial Rapid Release version 19 February 2002
  • Latest Rapid Release version 28 September 2010 revision 054
  • Initial Daily Certified version 19 February 2002
  • Latest Daily Certified version 28 September 2010 revision 036
  • Initial Weekly Certified release date 19 February 2002
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

This VBScript threat at first appears to be a "guess the number" game. If the script is run, you may see a dialog box, from which you can pick a number. (The numbers are randomly generated.)

The script may request that you play again. If you choose to do so, the script runs the additional code that is described in the rest of this write-up. If you do not play it again, then the script may exit harmlessly.

This mass-mailing VBScript may create the following files on the computer:
  • \Windows\System\GuessGame.vbe
  • \Windows\System\GuessGame.vbs
  • \Windows\System\GuessGame.bat

The script attempts to activate Microsoft Outlook. If it is successful, it searches the contacts folder and send email to each one that it finds. The email is in the following format:

Subject: Are you <contact name> my valentine?
Message : Hi <contact name> my valentine, remember me? I ain't seen you in ages! Anyway, check-out and play the attached guess-the-number-game to guess who I am. See you soon, bye-bye!"
Attachment: GuessGame.html (or GuessGame.vbe)

The script creates the GuessGame.bat file with instructions to set the system date to "04-08-1981".

The script attempts to disable system file protection in Windows NT/2000/XP by modifying the value of

SFCDisable

in the registry key

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon

The default setting of this value is "0", which enables this feature.

The script may also attempt to disable desktop icons or files by modifying or creating the value

NoDesktop

in the registry key

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer

The script carries a damaging file-deletion payload. It seeks files with the following extensions: .asp, .aspx, .cab, .com, .cpl, .dat, .dll, .doc, .drv, .exe, .hta, .htm, .html, .inf, .ini, .jpg, .mdb, .mp3, .ocx, .ppt, .sys, .txt, .vxd, and .xls, and attempts to delete them from several folders. The following folder names are based on installation and actual environment settings; names in quotes are hard coded in the script:
  • AllUsersDesktop
  • AllUsersPrograms
  • Desktop
  • MyDocuments
  • Programs
  • Windows
  • Windows\System
  • Temp
  • Windows\"COMMAND"
  • Windows\"INF"
  • Windows\"SYSBCKUP"
  • Windows\"SYSTEM32"
  • [root local drive]
  • [root local drive]\"My Documents"
  • [root local drive]\"Documents and Settings"
  • [root local drive]\"Program Files"
  • [root local drive]\"Inetpub"

The script continues with file deletion at the network level, attempting to delete all shared files and folders from available network drives, selecting every other one as a target.

This script also attempts to delete the following registry keys:

HKEY_CURRENT_USER\Control Panel
HKEY_CURRENT_USER\InstallLocationsMRU
HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer
HKEY_CURRENT_USER\Software\Microsoft\Office
HKEY_CURRENT_USER\Software\Microsoft\Windows
HKEY_CURRENT_USER\Software\ODBC
HKEY_LOCAL_MACHINE\Enum
HKEY_LOCAL_MACHINE\Software\Microsoft\Internet Explorer
HKEY_LOCAL_MACHINE\Software\Microsoft\Office
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows
HKEY_LOCAL_MACHINE\System

This script attempts to create a file-deletion-and-folder-removal Trojan as Autoexec.bat, and copy it to the root of all available mapped drives. The Autoexec.bat file contains instructions to search every folder on the local drive, delete all files, and then remove the folder.

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.

Obtain the most recent virus definitions. There are two ways to do this:
    • Run LiveUpdate. LiveUpdate is the easiest way to obtain virus definitions. These virus definitions have undergone full quality assurance testing by Symantec Security Response and are posted to the LiveUpdate servers one time each week (usually Wednesdays) unless there is a major virus outbreak. To determine if definitions for this threat are available by LiveUpdate, look at the Virus Definitions (LiveUpdate) line at the top of this write-up.
    • Download the definitions using the Intelligent Updater. Intelligent Updater virus definitions have undergone full quality assurance testing by Symantec Security Response. They are posted on U.S. business days (Monday through Friday). They must be downloaded from the Symantec Security Response Web site and installed manually. To determine if definitions for this threat are available by the Intelligent Updater, look at the Virus Definitions (Intelligent Updater) line at the top of this write-up.

      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.
  1. 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.
  2. Run a full system scan.
  3. Delete all files that are detected as VBS.Numgame@mm.

NOTE: If the script has run, it is likely that you will have to reinstall the operating system, most software, and restore .dat files from a clean backup.
Writeup By: Patrick Nolan