VBS.Boost@mm

SUMMARY

VBS.Boost@mm is an intended mass-mailing worm written in Microsoft Visual Basic (VB) Script that uses Microsoft Outlook to spread. There have been no reports of this worm in the wild.

Protection

• Virus Definitions (LiveUpdate™ Weekly) March 26, 2003
• Virus Definitions (Intelligent Updater) March 24, 2003

TECHNICAL DETAILS

VBS.Boost@mm is a mass-mailing worm that uses Microsoft Outlook to spread. When the worm is executed, it does the following:

1. Sends itself to all the addresses in the Outlook Address Book. The email has the following characteristics:
   
   Subject: Application Booster
   Message: Try the Free Application Boost Pack, NOW !!!!
   Attachment: Appboost.vbs or "Installation Program"
   
2. Adds the value:
   
   AppBoost WScript.exe <script name (usually Appboost.vbs)>
   
   to the registry key:
   
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionRun
   
   so that the worm runs when you start Windows.
   
3. Copies itself as Appboost.exe.
   
4. Changes the default value of the registry key:
   
   HKEY_CLASSES_ROOTexefileshellopencommand
   
   to:
   
   appboost.exe ""%1"" %*"
   
   This action forces the computer to run Appboost.exe before attempting to run any application with a .exe extension.
   
5. Writes itself as C:Test.exe (hard-coded).
   
6. May also write itself as:
   
   Appbsvc.exe
   Appboost.exe
   
   in the Desktop, My Documents, or Startup folders.

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.Boost@mm.
3. Delete and edit the values that were added to the registry.
   

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 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).
• 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).
  
  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.Boost@mm, click Delete.

3. Deleting and editing the values from the registry

CAUTION: Symantec strongly recommends that you back up the registry before you make any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify the specified keys only. Read the document, "How to make a backup of the Windows registry," for instructions.

1. Click Start, and then click Run. (The Run dialog box appears.)
2. Type regedit
   
   Then click OK. (The Registry Editor opens.)
   
3. Navigate to the key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
4. In the right pane, delete the value: AppBoost
5. Navigate to and select the key:
   
   HKEY_LOCAL_MACHINESoftwareClassesexefileshellopencommand
   
   NOTE: The HKEY_LOCAL_MACHINESoftwareClasses key contains many subkey entries that refer to other file extensions. One of these file extensions is .exe. Changing this extension can prevent any files ending with a .exe extension from running. Make sure that you completely browse through this path until you reach the command subkey.
   
   Modify the HKEY_LOCAL_MACHINESoftwareClassesexefileshellopencommand subkey, shown in the following figure:
   
   <<=== NOTE: Modify this key.
   
6. In the right pane, double-click the (Default) value.
7. Delete the current value data, and then type:
   
   "%1" %*
   
   That is, type the characters: quote-percent-one-quote-space-percent-asterisk.
   
   NOTES
   • Under Windows 95/98/Me/NT, the Registry Editor automatically encloses the value within quotation marks. When you click OK, the (Default) value should look exactly like this:
     
     ""%1" %*"  
     
   • Under Windows 2000/XP, the additional quotation marks will not appear. When you click OK, the (Default) value should look exactly like this:
     
     "%1" %*
     
   • Make sure that you completely delete all the value data in the command key before typing the correct data. If you leave a space at the beginning of the entry, any attempt to run the program files will result in the error message, "Windows cannot find .exe." If this occurs, restart the entire process from the beginning of this document and make sure that you completely remove the current value data.
     
8. Exit the Registry Editor.