Discovered: March 03, 2004
Updated: February 13, 2007 12:18:31 PM
Also Known As: W32/Mydoom.h@MM [McAfee], Win32.Mydoom.H [Computer Assoc, WORM_MYDOOM.H [Trend]
Type: Worm
Systems Affected: Windows

The W32.Mydoom.H@mm worm:

  • Is a mass-mailing worm that opens a backdoor on TCP ports 80 and 1080.
  • Can download and execute arbitrary files.
  • Performs a Denial of Service (DoS) against

The worm arrives as an attachment with the file extension .bat, .com, .cmd, .exe, .pif, .scr, or .zip. The From: line of the email may be spoofed.

  • Symantec Consumer products that support Worm Blocking functionality automatically detect this threat as it attempts to spread.
  • Virus definitions version 60302u (extended version 03/02/2004 rev 21) detect this threat as W32.Mydoom.G@mm.
  • W32.Mydoom.H@mm has an MD5 hash value of 0X47CC271E765E6CDF0562E692CE805B35.

Antivirus Protection Dates

  • Initial Rapid Release version March 04, 2004
  • Latest Rapid Release version May 31, 2016 revision 036
  • Initial Daily Certified version March 04, 2004
  • Latest Daily Certified version June 01, 2016 revision 005
  • Initial Weekly Certified release date March 10, 2004

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

Discovered: March 03, 2004
Updated: February 13, 2007 12:18:31 PM
Also Known As: W32/Mydoom.h@MM [McAfee], Win32.Mydoom.H [Computer Assoc, WORM_MYDOOM.H [Trend]
Type: Worm
Systems Affected: Windows

When W32.Mydoom.H@mm is executed, it does the following:

  1. Creates a mutex, "<string>theta," where <string> is a function of an infected computer's name. This allows only one instance of the worm to execute in memory.

  2. May create a file in the %Temp% folder that contains randomly generated data. The worm opens the file with Notepad.exe.

    Note: %Temp% is a variable. The worm locates the temporary folder and copies itself to that location. By default, this is C:\Windows\TEMP (Windows 95/98/Me), or C:\WINNT\Temp (Windows NT/2000), or C:\Document and Settings\<UserName>\Local Settings\Temp (Windows XP).

  3. Creates two files in the %System% folder:
    • <random>.exe or <random>.scr: A copy of the worm executable.
    • <random>.dll: A .dll file that implements the worm's backdoor functionality

      where <random> represents the file names, which are randomly generated and consist of one upper- or lower-case letter, followed by a varying number of lower-case letters. For example: Abcde.dll or fghi.exe.

      Note: %System% is a variable: The worm locates the System folder and copies itself to that location. By default, this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).

  4. Opens a backdoor listening on TCP ports 80 and 1080, using the .dll component, which acts as a proxy server and can also download and execute the arbitrary files.

  5. Terminates numerous processes and attempts to delete the associated files. The worm targets the processes and files that antivirus software uses, and some associated with other worms.

    The worm terminates the following processes by name:
    • adaware.exe
    • alevir.exe
    • arr.exe
    • au.exe
    • backweb.exe
    • bargains.exe
    • belt.exe
    • blss.exe
    • bootconf.exe
    • bpc.exe
    • brasil.exe
    • bundle.exe
    • bvt.exe
    • cfd.exe
    • cmd32.exe
    • cmesys.exe
    • datemanager.exe
    • dcomx.exe
    • divx.exe
    • dllcache.exe
    • dllreg.exe
    • dpps2.exe
    • dssagent.exe
    • emsw.exe
    • explore.exe
    • fsg_4104.exe
    • gator.exe
    • gmt.exe
    • hbinst.exe
    • hbsrv.exe
    • hotfix.exe
    • hotpatch.exe
    • htpatch.exe
    • hxdl.exe
    • hxiul.exe
    • idle.exe
    • iedll.exe
    • iedriver.exe
    • iexplorer.exe
    • inetlnfo.exe
    • infus.exe
    • infwin.exe
    • init.exe
    • intdel.exe
    • isass.exe
    • istsvc.exe
    • jdbgmrg.exe
    • kazza.exe
    • keenvalue.exe
    • kernel32.exe
    • launcher.exe
    • lnetinfo.exe
    • loader.exe
    • mapisvc32.exe
    • md.exe
    • mfin32.exe
    • mmod.exe
    • mostat.exe
    • msapp.exe
    • msbb.exe
    • msblast.exe
    • mscache.exe
    • msccn32.exe
    • mscman.exe
    • msdm.exe
    • msdos.exe
    • msiexec16.exe
    • mslaugh.exe
    • msmgt.exe
    • msmsgri32.exe
    • msrexe.exe
    • mssys.exe
    • msvxd.exe
    • netd32.exe
    • nssys32.exe
    • nstask32.exe
    • nsupdate.exe
    • onsrvr.exe
    • optimize.exe
    • patch.exe
    • pgmonitr.exe
    • powerscan.exe
    • prizesurfer.exe
    • prmt.exe
    • prmvr.exe
    • ray.exe
    • rb32.exe
    • rcsync.exe
    • run32dll.exe
    • rundll.exe
    • rundll16.exe
    • ruxdll32.exe
    • sahagent.exe
    • save.exe
    • savenow.exe
    • sc.exe
    • scam32.exe
    • scrsvr.exe
    • scvhost.exe
    • service.exe
    • servlce.exe
    • servlces.exe
    • showbehind.exe
    • sms.exe
    • smss32.exe
    • soap.exe
    • spoler.exe
    • spoolcv.exe
    • spoolsv32.exe
    • srng.exe
    • ssgrate.exe
    • start.exe
    • stcloader.exe
    • support.exe
    • svc.exe
    • svchostc.exe
    • svchosts.exe
    • svshost.exe
    • system.exe
    • system32.exe
    • sysupd.exe
    • teekids.exe
    • trickler.exe
    • tsadbot.exe
    • tvmd.exe
    • tvtmd.exe
    • webdav.exe
    • win-bugsfix.exe
    • win32.exe
    • win32us.exe
    • winactive.exe
    • window.exe
    • windows.exe
    • wininetd.exe
    • wininit.exe
    • wininitx.exe
    • winlogin.exe
    • winmain.exe
    • winnet.exe
    • winppr32.exe
    • winservn.exe
    • winssk32.exe
    • winstart.exe
    • winstart001.exe
    • wintsk32.exe
    • winupdate.exe
    • wnad.exe
    • wupdater.exe
    • wupdt.exe

      and any processes containing the following strings:
    • avpupd
    • avwupd
    • beagle
    • click
    • d3du
    • f**k (censored)
    • hotactio
    • intren
    • penis
    • porn
    • pussy
    • reged
    • sperm
    • taskmg
    • taskmo
    • updat
    • upgrad
    • utpost.
    • wkufind

  6. Iterates through all the drives (hard drive, remote drive, or RAM drive), C through Z, and does one of the following:
    • Creates randomly named copies of itself as a .exe file in randomly selected folders.
    • Creates .zip archive files using randomly generated file names.

  7. Adds the value:

    "<random lowercase letters>" = "%System%\<the filename of the worm>"

    to one of these registry keys:
    • HKEY_CURRENT_USER\Software\Microsft\Windows\CurrentVersion\Run
    • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

      so that the worm runs when you restart Windows.

  8. Adds the value:

    "(Default)" = "%System%\<random dll filename>.dll"

    to the registry keys:
    • HKEY_CLASSES_ROOT\CLSID\{E6FB5E20-DE35-11CF-9C87-00AA005127ED}\
    • HKEY_CLASSES_ROOT\CLSID\{35CEC8A3-2BE6-11D2-8773-92E220524153}\

      so that Explorer.exe loads the backdoor dll.

  9. Checks for the existence of the file, C:\Feedlist. If this file does not exist, the worm attempts to perform a DoS attack against or This routine begins 10-20 minutes after the worm is first executed. The DoS is performed by creating between 8-80 new threads that send GET requests and use a direct connection to port 80. There is no cut-off date for the DoS.

  10. Searches drives C to Z for the files with the following extensions:
    • .avi
    • .doc
    • .jpg
    • .mp3
    • .mp4
    • .wav
    • .wma
    • .xls

      The worm creates new copies of itself, using the file names it finds, plus a .exe or .scr extension.

      For example, if it finds a file named "file.doc," it may copy itself as "file.doc.exe." In addition, it may overwrite some .pif files.

  11. Searches drives C to Z for the files that have the following extensions, and for any files whose names contain "Inbox:"
    • .adb
    • .asp
    • .dbx
    • .eml
    • .htm
    • .mbx
    • .mht
    • .mmf
    • .msg
    • .nch
    • .php
    • .rtf
    • .sht
    • .tbb
    • .txt
    • .uin
    • .wab

      If the drive is a hard drive or RAM drive, the worm will retrieve the email addresses from the files it finds.

  12. Retrieves the email addresses from the %Temporary Internet Files% folder and the Windows address book.

    Note: %Temporary Internet Files% is a variable. The worm locates the Temporary Internet Files folder and copies itself to that location. By default, this is C:\Windows\Temporary Internet Files (Windows 95/98/Me), or C:\Document and Settings\<UserName>\Local Settings\Temporary Internet Files (Windows NT/2000/XP).

  13. The worm avoids the email addresses that contain certain strings, including:
    • berkeley
    • bsd
    • fsf.
    • gnu.
    • google.
    • kernel.
    • mozilla.
    • packetstorm
    • rfc-edit
    • secur
    • sendmail.
    • slashdot.
    • sourceforge
    • unix
    • urlon
    • ymante

  14. Uses its own engine to send itself, or its .zip archive, to the email addresses it finds. The email has the following characteristics:

    From: (The senders name may be one of the following)
    • alex
    • bill
    • bob
    • james
    • john
    • kevin
    • peter
    • sales
    • sales
    • sales
    • sam
    • stan
    • tom
    • <random characters>

      with one of the following domains:
    • <random characters>.edu

      Note: The worm may also use the email addresses it finds from the local files.

      Subject: (One of the following)
    • <blank>
    • :)
    • :-)
    • Address verification
    • Alert
    • Attention
    • Auto-reply
    • Automatic notification
    • Bank information
    • Daily Report
    • Email verification
    • Empty
    • Expired account
    • For your eyes only
    • Interesting
    • Micro$oft
    • Microsoft
    • Please, confirm the registration
    • Registration
    • Registration rejected
    • Rejected
    • Reply
    • Request
    • Response
    • See you soon
    • Warning
    • You have been successfully registered
    • Your account details
    • Your account is about to be expired
    • Your account is expired
    • Your details
    • Your profile
    • Your request
    • Your request
    • account details
    • anna
    • beauty
    • confirmed
    • corrupted
    • dear friend!
    • details
    • do you love me
    • do you still love me
    • document
    • excel
    • excuse me
    • from me
    • fw:
    • greetings
    • hello
    • hello
    • hello my friend
    • hello! :)
    • here
    • here is the document
    • hey
    • hey!
    • hi!
    • hi! :)
    • how are you?
    • i can tell you the future
    • i need you
    • important
    • jessica
    • join
    • just some stuff
    • kate
    • kleopatra
    • maria
    • melissa
    • message
    • micro$oft must die. support us!
    • missed
    • my details
    • my photos
    • notification
    • pamela
    • photo
    • please read
    • price
    • price list
    • price-list
    • pricelist
    • question
    • re:
    • read!!!
    • report
    • see you
    • service
    • some stuff
    • spreadsheet
    • stuff
    • summary
    • thank you
    • thanks
    • thanks!
    • unknown
    • verification
    • we're experiencing technical problems
    • we're unable to process your request
    • your account
    • your archive
    • your chance
    • your document
    • your letter
    • your music
    • your website

      Message: (One of the following)
    • Details are in the attached document
    • Full message is in the attached documen
    • Here is the document
    • Here is the file
    • Here it is
    • Hi! Check the attachment for details
    • Look at the attached file
    • Look at the document
    • Ok
    • Okay
    • Open the document
    • Please have a look at the attached file
    • Please read the attached file
    • Please, read and let me know what do yo
    • Please, reply
    • Re:
    • Read the attached message
    • Read the document
    • Read this
    • See attachemnt
    • See attachment
    • See the attached document
    • See the attached file for details
    • See the attached message
    • See you
    • Test
    • Your document is attached
    • Your file is attached
    • test

      Attachment: (The attachment name is randomly constructed. The base file name is selected from the following.)
    • AttachedDocument
    • AttachedFile
    • Document
    • Letter
    • MoreInfo
    • TextDocument
    • TextFile
    • account
    • all_document
    • application
    • archive
    • att
    • attach
    • attachment
    • bill
    • check
    • description
    • details
    • doc
    • document
    • file
    • for_you
    • found
    • id
    • important
    • info
    • information
    • letter
    • mail
    • message
    • message_details
    • message_part2
    • misc
    • more
    • msg
    • msg2
    • music
    • news
    • news
    • no
    • note
    • object
    • part2
    • payment
    • paypal
    • pic
    • post
    • posting
    • price
    • problem
    • ps
    • readme
    • reply
    • response
    • stuff
    • test

      The file extension is selected from the following:
    • exe
    • scr
    • pif
    • cmd
    • bat
    • com
    • zip

      The file name may include random numbers: For example, "readme4859.scr." The attachment may have two extensions, as with previous variants of Mydoom.

      The worm may use the following icon to deceive users of its true file type:


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.

Discovered: March 03, 2004
Updated: February 13, 2007 12:18:31 PM
Also Known As: W32/Mydoom.h@MM [McAfee], Win32.Mydoom.H [Computer Assoc, WORM_MYDOOM.H [Trend]
Type: Worm
Systems Affected: Windows

Removal using the Removal Tool
Symantec Security Response has developed a removal tool to clean the infections of variants of W32.Novarg/Mydoom. This is the preferred method in most cases.

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. Restart the computer in Safe mode or VGA mode.
  4. Run a full system scan and delete all the files detected as W32.Mydoom.H@mm.
  5. Delete the values that were added to the registry.
  6. Reregistering the Windows .dll files
For specific details on each of these steps, read the following instructions.

1. Disabling 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:
Note: 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. 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: Read "How to update virus definition files using the Intelligent Updater" for detailed instructions.

3. Restarting the computer in Safe mode or VGA mode

Shut down the computer and turn off the power. Wait for at least 30 seconds, and then restart the computer in Safe mode or VGA mode.
  • For Windows 95, 98, Me, 2000, or XP users, restart the computer in Safe mode. For instructions, read the document, "How to start the computer in Safe Mode."
  • For Windows NT 4 users, restart the computer in VGA mode.

4. 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.
  2. Run a full system scan.
  3. If any files are detected as infected with W32.Mydoom.H@mm, click Delete.

5. Deleting the values from the registry

WARNING: 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, and then click Run. (The Run dialog box appears.)
  2. Type regedit

    Then click OK. (The Registry Editor opens.)

  3. Navigate to each of these keys:



  4. In the right pane, delete the value that the worm added:

    "<random, lowercase letters>" = "%System%\<the filename of the worm>"

  5. Exit the Registry Editor.

6. Reregistering the Windows .dll files
This will remove the registry modifications responsible for loading the backdoor .dll file and restore the default settings.
  1. Click Start, and then click Run. (The Run dialog box appears.)
  2. Type, or copy and paste, the following text:

    regsvr32 webcheck.dll

  3. Click OK. When you see the message, "DllRegisterServer in webcheck.dll succeeded," click OK.
  4. Click Start, and then click Run.
  5. Type, or copy and paste, the following text:

    regsvr32 stobject.dll

  6. Click OK. When you see the message, "DllRegisterServer in stobject.dll succeeded," click OK.