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Discovered: September 14, 2004
Updated: February 13, 2007 12:27:31 PM
Also Known As: Win32.Mydoom.Z [Computer Assoc, Email-Worm.Win32.Mydoom.x [Kas, W32/Mydoom.gen@MM [McAfee], W32/MyDoom-X [Sophos], WORM_MYDOOM.X [Trend Micro]
Type: Worm
Systems Affected: Windows

W32.Mydoom.W@mm is a mass-mailing worm that attempts to perform a Distributed Denial of Service (DDoS) attack against www.symantec.com.

Antivirus Protection Dates

  • Initial Rapid Release version September 14, 2004
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version September 14, 2004
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date September 15, 2004

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

Technical Description

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

  1. Creates the following registry keys:


  2. Creates the mutex "Sept-Symantec-Attack" so that only one instance of the worm can be executed.

  3. Deletes the files in the Windows Temp folder.

  4. Inserts the following files:
    • %Temp%\Services.exe: This file will be detected as Backdoor.Zincite.A.
    • %System%\About_Mydoom.txt: This is a text file and should be manually deleted.
    • %System%\Doompic.jpg: This is a JPEG file and should be manually deleted.
    • %System%\log32zx.exe: This file will be detected as Keylogger.Trojan.
    • %System%\Downxz.bat: This file will be detected as Download.Trojan.

  5. Copies itself as:
    • %System%\oz11111.exe
    • %Windir%\oz2.exe

  6. Adds the following values:

    "Microsoft Windows updaterD"="%system%\log32zx.exe"

    to one of these registry keys:


  7. Performs a DDoS attack against www.symantec.com by sending a GET request on TCP port 80 every 300ms between 9/1/2004 and 10/1/2004.

  8. Querys the registry entry HKEY_CURRENT_USER\Software\Kazaa\Transfer\DlDir0, and, if successful, it will attempt to copy itself to that folder as <filename>.<ext>.

    where <filename> is one of the following:
    • Virus
    • XXX Pictures
    • XXX Videos
    • xbox emulator
    • ps2 emulator
    • Hotmail hacker
    • yahoo hacker
    • klez
    • SoBig
    • mydoom
    • netsky
    • Upload
    • crack
    • Winzip
    • kazz
    • Winrar
    • mirc
    • cleaner
    • SeX
    • Vaho
    • Fixtool
    • Winamp

      and <ext> is one of the following string:
    • exe
    • scr
    • pif
    • bat

  9. Retrieves email addresses from the Microsoft Outlook Address Book, and from files on fixed disks, ram disks, and in the following folders:
    • %userprofile%\Local Settings\Temporary Internet Files
    • %userprofile%\Desktop
    • %userprofile%\My Documents
    • %userprofile%\Application Data
    • %windir%\Temporary Internet Files
    • %windir%\Desktop
    • %windir%\My Documents
    • %windir%\Application Data
    • %system%

      The worm also queries the registry key:

      HKEY_CURRENT_USER\Software\Microsoft\WAB\WAB4\Wab File Name

      and searches the folders found listed in the key for the email addresses.

      The worm only looks for the email addresses in the files that have the following extensions:
    • txt
    • htm
    • htm
    • mbx
    • mdx
    • xml
    • jsp
    • xls
    • uin
    • msg
    • wsh
    • cgi
    • eml
    • cfg
    • vbs
    • sht
    • php
    • asp
    • dbx
    • tbb
    • adb
    • pl
    • wab

      The worm will ignore any email address that contain the following strings:
    • avp
    • syma
    • icrosof
    • panda
    • sopho
    • borlan
    • inpris
    • example
    • mydomai
    • nodomai
    • ruslis
    • .gov
    • gov.
    • .mil
    • foo.
    • berkeley
    • unix
    • math
    • bsd
    • mit.e
    • gnu
    • fsf.
    • ibm.com
    • kernel
    • linux
    • fido
    • usenet
    • iana
    • ietf
    • rfc-ed
    • sendmail
    • arin.
    • ripe.
    • isi.e
    • isc.o
    • acketst
    • pgp
    • tanford.e
    • utgers.ed
    • mozilla
    • spm
    • spam
    • www
    • secur
    • abuse
    • admin
    • microsoft
    • support
    • ntivi
    • unix
    • bsd
    • linux
    • listserv
    • certific
    • google
    • account
    • root
    • info
    • samples
    • postmaster
    • webmaster
    • noone
    • nobody
    • nothing
    • anyone
    • someone
    • your
    • you
    • me
    • bugs
    • rating
    • site
    • contact
    • soft
    • no
    • somebody
    • privacy
    • service
    • help
    • not
    • submit
    • feste
    • ca
    • gold-certs
    • the.bat
    • page

  10. Uses its own SMTP engine to send itself to the email addresses that it finds.

    Note: If the server name of the recipients is <hostname>, the worm will attempt to use one of the following servers as the SMTP server:
    • mx.<hostname>
    • mail.<hostname>
    • smtp.<hostname>
    • mx1.<hostname>
    • mxs.<hostname>
    • mail1.<hostname>
    • replay.<hostname>
    • ns.<hostname>
    • gate.<hostname>
    • mx2.<hostname>
    • mx3.<hostname>
    • mx4.<hostname>

      The email has the following characteristics:

      The From address is spoofed. It may create an email address using one of the following names or a random name:
    • Leon
    • Tom
    • Marcus
    • Troy
    • Walter
    • Eric
    • Matthew
    • Kenneth
    • Charles
    • Tommy
    • Jim
    • Francisco
    • Ricky
    • Dennis
    • Scott
    • Jason
    • George
    • Richard
    • Lloyd
    • Jay
    • Leroy
    • Carl
    • Jerry
    • Frank
    • Kevin
    • Donald
    • David
    • Bill
    • Oscar
    • Mario
    • Henry
    • Joshua
    • Jeffrey
    • Anthony
    • Mark
    • William
    • Ronnie
    • Miguel
    • Bernard
    • Douglas
    • Gregory
    • Larry
    • Ronald
    • Paul
    • Michael
    • Jon
    • Clifford
    • Alexander
    • Harold
    • Raymond
    • Jose
    • Brian
    • Daniel
    • Robert
    • Alex
    • Theodore
    • Barry
    • Peter
    • Andrew
    • Timothy
    • Edward
    • Thomas
    • John
    • Calvin
    • Micheal
    • Randall
    • Patrick
    • Stephen
    • Gary
    • Steven
    • JosephJames

      followed by one of the following:
    • _1
    • _22
    • _33
    • _44
    • _16
    • _22
    • _98
    • _26
    • _12

      and will include one of the following domains:
    • aol.com
    • msn.com
    • yahoo.com
    • hotmail.com
    • cox.net
    • yahoo.co.uk
    • mail.com
    • t-online.de
    • dailymail.co.uk

      Attachment: <filename>    .<ext>

      <filename> is one of the following:
    • message.qbp
    • letter.qbp
    • report.qbp
    • bqc.qbp
    • bqcument.qbp
    • information.qbp
    • error.qbp
    • Fix.qbp
    • check.qbp
    • read.qbp
    • screen.qbp
    • file.qbp

      <ext> is one of the following:
    • pif
    • scr
    • exe
    • cmd
    • bat

      Subject: (One of the following)
    • Re:Help
    • Hi
    • FW:Hi
    • Hello
    • Re:Test
    • Failn
    • Delivery status Notification
    • Important
    • Re:Important
    • FW:Important
    • Information
    • FW:Information
    • Re:Information
    • Read
    • FW:Read
    • Re:Read
    • Re:Question
    • Re:Hi
    • Hi!
    • News
    • Re:News
    • Thanks
    • Re:Thanks
    • FW:Thanks
    • Re:Hello!
    • Hello
    • Hello!
    • FW:Hello


      +++ Attachment: No Virus found                 (or +++ Attachment: No Infection found)

      where <msg> is one of the following:
    • test
    • Please read the important document.
    • I have attached document.
    • Waiting for a Response. Please read the attachment.
    • Thanks!
    • Please see the attached file for details
    • Please read the attached file!
    • Please confirm!
    • Please answer quickly!
    • For more details see the attachment.
    • For further details see the attachment.
    • Monthly news report.
    • Virus removal tool
    • apply this patch!
    • fun game!
    • lol!
    • fun!
    • See the file.
    • screensaverlol!
    • See the file.
    • Your archive is attached.
    • check!
    • Error
    • !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
    • Hello Check the attachment.
    • Here is the attachment.
    • :-)
    • Here is my photo.:-)

      and <avprod> is one of the following:
    • Norton AntiVirus - www.symantec.com
    • F-Secure AntiVirus - www.f-secure.com
    • Norman AntiVirus - www.norman.com
    • Panda AntiVirus - www.pandasoftware.com
    • Kaspersky AntiVirus - www.kaspersky.com
    • MC-Afee AntiVirus - www.mcafee.com
    • Bitdefender AntiVirus - www.bitdefender.com
    • MessageLabs AntiVirus - www.messagelabs.com


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.


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 as W32.Mydoom.W@mm.
  4. Delete the value that was 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, re-enable 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 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 Virus Definitions (Intelligent Updater).

    The Intelligent Updater virus definitions are available: Read "How to update virus definition files using the Intelligent Updater" for detailed instructions.

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 as infected with W32.Mydoom.W@mm, click Delete.

    If your Symantec antivirus product reports that it cannot delete an infected 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, you can leave the computer in Safe mode and proceed with section 4. When that is done, restart the computer in Normal mode.)

4. To delete the value from the registry

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 keys only. Read the document, "How to make a backup of the Windows registry ," for instructions.
  1. Click Start > Run.
  2. Type regedit

    Then click OK.

  3. Navigate to these keys:


  4. In the right pane, delete these values:

    "Microsoft Windows updaterD"="%system%\log32zx.exe"

  5. Exit the Registry Editor.

Writeup By: Robert X Wang