Discovered: May 08, 2005
Updated: February 13, 2007 12:38:37 PM
Also Known As: Win32.Mytob.{CO, CS} [Computer Associates], [Kaspe, W32/Mytob.gen@MM [McAfee], W32/Mytob-{BC, CF} [Sophos], WORM_MYTOB.{EC, ED} [Trend Micro]
Type: Worm
Systems Affected: Windows

W32.Mydoom.BO@mm is a worm that uses its own SMTP engine to send an email to addresses that it gathers from the compromised computer. The worm also opens a back door on TCP port 6677.

Removing entries from the Hosts file
If this threat has modified the Windows Hosts file, there are two ways to remove these entries:

  • Install and run the current version of LiveUpdate. This will remove only the entries that refer to Symantec domains.
  • Manually edit the Hosts file and remove all the entries that the threat added.

To run the current version of LiveUpdate
  1. Click download LiveUpdate.

    If you are not reading this Web page on the computer that is getting the error notice, the address for downloading the file is:

    If necessary, you can type this address into the address bar of the problem computer. Changes to the Hosts file will not stop you from getting to this site.

  2. Save the file to the Windows desktop.
  3. Double-click the lusetup.exe icon on the desktop to install LiveUpdate.
  4. Run LiveUpdate.
  5. Did you see the message "LU1860: LiveUpdate has detected a potential security compromise on your computer"?
    • If you did, let LiveUpdate "Remove these entries from the hosts files" (Recommended).
      This should allow LiveUpdate to run.
    • If you did not, that was not the cause of the problem. Return to the Removal section.

To manually edit the Hosts file and remove all the entries that the risk added

Note: The location of the Hosts file may vary and some computers may not have this file. For example, if the file exists in Windows 98, it will usually be in C:\Windows; and it is located in the C:\WINNT\system32\drivers\etc folder in Windows 2000. There may also be multiple copies of this file in different locations.

Follow the instructions for your operating system:
  • Windows 95/98/Me/NT/2000
    1. Click Start, point to Find or Search, and then click Files or Folders.
    2. Make sure that "Look in" is set to (C:) and that "Include subfolders" is checked.
    3. In the "Named" or "Search for..." box, type:


    4. Click Find Now or Search Now.
    5. For each Hosts file that you find, right-click the file, and then click Open With.
    6. Deselect the "Always use this program to open this program" check box.
    7. Scroll through the list of programs and double-click Notepad.
    8. When the file opens, delete all the entries added by the risk. (See the Technical Details section for a complete list of entries.)
    9. Close Notepad and save your changes when prompted.

Antivirus Protection Dates

  • Initial Rapid Release version May 08, 2005
  • Latest Rapid Release version January 27, 2018 revision 020
  • Initial Daily Certified version May 08, 2005
  • Latest Daily Certified version January 28, 2018 revision 007
  • Initial Weekly Certified release date May 09, 2005

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

Writeup By: Eric Chien

Discovered: May 08, 2005
Updated: February 13, 2007 12:38:37 PM
Also Known As: Win32.Mytob.{CO, CS} [Computer Associates], [Kaspe, W32/Mytob.gen@MM [McAfee], W32/Mytob-{BC, CF} [Sophos], WORM_MYTOB.{EC, ED} [Trend Micro]
Type: Worm
Systems Affected: Windows

When W32.Mydoom.BO@mm is executed, it performs the following actions.

  1. Copies itself as %System%\1hellbot.exe.

    Note: %System% is a variable that refers to the System folder. By default this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).

  2. Adds the value:

    "HELLBOT TEST" = "1hellbot.exe"

    to the registry subkeys:


    so that the threat runs every time Windows starts.

  3. Creates the mutex named "H-e-l-l-B-o-t-3-!!!", so that only one instance of the threat runs on the compromised computer

  4. Opens a back door by connecting to an IRC channel on the domain using TCP port 6677. This allows the remote attacker to perform any of the following actions:

    • Download and execute files.
    • Perform other IRC commands determined by the attacker.
    • Reboot the compromised computer.

  5. Retrieves email addresses from the Windows Address Book and from the following locations:

    • %Windir%\Temporary Internet Files
    • %UserProfile%\Local Settings\Temporary Internet Files
    • %System%

      %Windir% is a variable that refers to the Windows installation folder. By default, this is C:\Windows (Windows 95/98/Me/XP) or C:\Winnt (Windows NT/2000).
      %UserProfile% is a variable that refers to the current user's profile folder. By default, this is C:\Documents and Settings\<Current User> (Windows NT/2000/XP).

      The worm also searches all local drives from C to Y for email addresses in files that have the following extensions:

    • htm*
    • sht*
    • php
    • asp
    • dbx
    • tbb
    • adb
    • wab
    • txt

  6. Attempts to send itself as and email using its own SMTP engine. The email will have the following characteristics:

    One of the following, with a .edu domain:
    • john
    • alex
    • michael
    • james
    • mike
    • kevin
    • david
    • george
    • sam
    • andrew
    • jose
    • leo
    • maria
    • jim
    • brian
    • serg
    • mary
    • ray
    • tom
    • peter
    • robert
    • bob
    • jane
    • joe
    • dan
    • dave
    • matt
    • steve
    • smith
    • stan
    • bill
    • bob
    • jack
    • fred
    • ted
    • adam
    • brent
    • alice
    • anna
    • brenda
    • claudia
    • debby
    • helen
    • jerry
    • jimmy
    • julie
    • linda
    • sam

      The worm may also spoof an address from one of those found on the computer.

      One of the following: 

    • Notice: **Last Warning**
    • Your email account access is restricted
    • Your Email Account is Suspended For Security Reasons
    • Notice:***Your email account will be suspended***
    • Security measures
    • Email Account Suspension
    • *IMPORTANT* Please Validate Your Email Account
    • *IMPORTANT* Your Account Has Been Locked

      Message body: 
      One of the following: 

    • Once you have completed the form in the attached file , your account records will not be interrupted and will continue as normal.
    • To unblock your email account acces, please see the attachement.
    • Please see the attachement.
    • We have suspended some of your email services, to resolve the problem you should read the attached document.
    • To safeguard your email account from possible termination, please see the attached file.
    • please look at attached document.
    • Account Information Are Attached!

      One of the following: 

    • email-doc
    • info
    • text
    • doc
    • your_details
    • document_full
    • INFO
    • info-text

      With one of the following file extensions:

    • .pif
    • .scr
    • .exe
    • .cmd
    • .bat
    • .zip

      Note: If the attachment is a .zip file, a copy of the worm is contained within. The file name within the .zip file is the same as the .zip file.

  7. Attempts to end the following processes, some of which may be security related:

    • regedit.exe
    • msconfig.exe
    • cmd.exe
    • taskmgr.exe
    • netstat.exe
    • zapro.exe
    • navw32.exe
    • navapw32.exe
    • zonealarm.exe
    • wincfg32.exe
    • PandaAVEngine.exe

  8. Adds the following text to the Hosts file to block access to several security-related Web sites:
    -=Copyright (C) 2005-2006 [REMOVED] Team All Rights Reserved.=-


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: Eric Chien

Discovered: May 08, 2005
Updated: February 13, 2007 12:38:37 PM
Also Known As: Win32.Mytob.{CO, CS} [Computer Associates], [Kaspe, W32/Mytob.gen@MM [McAfee], W32/Mytob-{BC, CF} [Sophos], WORM_MYTOB.{EC, ED} [Trend Micro]
Type: Worm
Systems Affected: Windows

Removal using the W32.Mydoom@mm Removal Tool
Symantec Security Response has developed a removal tool to clean the infections of W32.Mydoom.BO@mm. Use this removal tool first, as it is the easiest way to remove this threat.

Manual Removal:
The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

  1. Disable System Restore (Windows Me/XP).
  2. Update the virus definitions.
  3. Run a full system scan and delete all the files detected.
  4. Delete any values added to the registry.
For specific details on each of these steps, read the following instructions.

1. To disable System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:
When you are completely finished with the removal procedure and are satisfied that the threat has been removed, reenable System Restore by following the instructions in the aforementioned documents.

For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article: Antivirus Tools Cannot Clean Infected Files in the _Restore Folder (Article ID: Q263455).

2. To update 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 document: Virus Definitions (LiveUpdate).
  • Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted daily. 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 document: Virus Definitions (Intelligent Updater).

    The latest Intelligent Updater virus definitions can be obtained here: Intelligent Updater virus definitions. For detailed instructions read the document: How to update virus definition files using the Intelligent Updater.

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

    Note: If your Symantec antivirus product reports that it cannot delete a detected file, Windows may be using the file. To fix this, run the scan in Safe mode. For instructions, read the document: How to start the computer in Safe Mode. Once you have restarted in Safe mode, run the scan again.

    After the files are deleted, restart the computer in Normal mode and proceed with the next section.

    Warning messages may be displayed when the computer is restarted, as the threat has not been fully removed at this point. Please ignore these messages and just click OK. These messages will not appear when the computer is restarted after the removal instructions have been fully completed. The messages displayed may be similar to the following:

    Title: [File path]
    Message body: Windows cannot find [file name]. Make sure you typed the name correctly, and then try again. To search for a file, click the Start button, and then click Search.

4. To delete the value from the registry
Important: Symantec strongly recommends that you back up the registry before making any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify the specified subkeys only. For instructions refer to the document: How to make a backup of the Windows registry.
  1. Click Start > Run.
  2. Type regedit
  3. Click OK.

    Note: If the registry editor fails to open the threat may have modified the registry to prevent access to the registry editor. Security Response has developed a tool to resolve this problem. Download and run this tool, and then continue with the removal.

  4. Navigate to the subkey:


  5. In the right pane, delete the value:

    "HELLBOT TEST" = "1hellbot.exe"

  6. Navigate to the subkey:


  7. In the right pane, delete the value:

    "HELLBOT TEST" = "1hellbot.exe"

  8. Exit the Registry Editor.

Writeup By: Eric Chien