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26 November 2002
13 February 2007
Systems Affected:

VBS.Hypoth@mm is a mass-mailing worm that uses Microsoft Outlook to email itself. It infects .vbs and .vbe files and renames audio and video files.

Antivirus Protection Dates

  • Initial Rapid Release version 26 November 2002
  • Latest Rapid Release version 28 September 2010 revision 054
  • Initial Daily Certified version 26 November 2002
  • Latest Daily Certified version 28 September 2010 revision 036
  • Initial Weekly Certified release date 26 November 2002
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

VBS.Hypoth@mm copies itself to the \Windows\System folder as one or more of the following file names:
  • Runmsdsk32.vbs
  • Sitelist.vbs
  • Winnt32.vbs
  • Jokes.vbs
  • Confidential.vbs
  • Runmnt32.vbs
  • Holidaypics.vbs
  • Securityupdate.vbs
  • Update.vbs
  • Updatesecurity.vbs
  • Updateinstaller.vbs
  • Updatesetup.vbs
  • Readme.vbs
  • <random characters>.vbs

It adds one of these values, with a value data that refers to one of the files in the previous list:


to the registry key


so that the worm runs when you start Windows.

Next, using MAPI, it uses Microsoft Outlook to send email to all addresses in the Outlook Address Book. It records addresses of the sent email in the registry key


so that the worm only mails itself once to each address.

The email will be one of the following:

Subject: Hey <Recipient's Name>!
Message Body:
<Recipient's Name>! Get free mp3s from the web site that i go to! I can get almost any music that I want, just look at all the cool sites that I went to in the attachments.
Attachment: Sitelist.vbs

Subject:   Hello <Recipient's Name>!
Message Body:
Have fun with these great jokes!
<Sender's Name>
Attachment: Jokes.vbs

Subject: Here is that file you wanted, <Recipient's Name>.
Message Body:
This is the file you wanted - don't let anyone else see it!
<Sender's Name>
Attachment: Confidential.vbs

Subject: Check this out, <Recipient's Name>!
Message Body:
Hello <Recipient's Name>, check out these pictures of my last holiday! Don't get jealous!
<Sender's Name>
Attachment: Holidaypics.vbs

Subject: Urgent Update!
Message Body:
<Recipient's Name>,
Your computer will need this update to protect your computer from new email viruses. I installed this update and it works fine.
Attachment: SecurityUpdate.vbs, Update.vbs, UpdateSecurity.vbs, UpdateInstaller.vbs, UpdateSetup.vbs, or Readme.vbs

After sending itself out by email, the worm searches all drives for .vbs or .vbe files and appends an obfuscated version of itself to those files.

Finally, the worm adds the extension .vbs to all .mp3, .mp2, .mpg, .mpe, .mpeg, .avi, and .mov files. For example, Song.mp3 would become Song.mp3.vbs. The worm may append itself to these files on subsequent executions and potentially corrupt the audio and video files.


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.

NOTE: These instructions are for 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.
  3. Delete all files that are detected as VBS.Hypoth@mm.
  4. Delete the value that it added to the registry key

For details on how to do this, read the following instructions.

To update the virus definitions:
All virus definitions receive full quality assurance testing by Symantec Security Response before being posted to our servers. There are two ways to obtain the most recent virus definitions:
  • Run LiveUpdate, which is the easiest way to obtain virus definitions. These virus definitions are posted to the LiveUpdate servers once each week (usually Wednesdays) unless there is a major virus outbreak. To determine whether 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 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 whether 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.

To scan for and delete the infected files:
  1. Start your Symantec antivirus program, and make sure that it is configured to scan all files.
  2. Run a full system scan.
  3. If any files are detected as infected with VBS.Hypoth@mm, click Delete.

To delete the value 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 only the keys that are specified. Read the document How to make a backup of the Windows registry for instructions.
  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 key

  4. In the right pane, delete any of these values:

  5. Exit the Registry Editor.

Writeup By: Eric Chien